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WO2025014948A2 - Catalyst compositions and methods thereof - Google Patents

Catalyst compositions and methods thereof Download PDF

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Publication number
WO2025014948A2
WO2025014948A2 PCT/US2024/037204 US2024037204W WO2025014948A2 WO 2025014948 A2 WO2025014948 A2 WO 2025014948A2 US 2024037204 W US2024037204 W US 2024037204W WO 2025014948 A2 WO2025014948 A2 WO 2025014948A2
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WIPO (PCT)
Prior art keywords
compound
formula
certain embodiments
ring
light
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French (fr)
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WO2025014948A3 (en
Inventor
Richard R. Schrock
Matthew P. Conley
Rene Riedel
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University of California Berkeley
University of California San Diego UCSD
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University of California Berkeley
University of California San Diego UCSD
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Publication of WO2025014948A2 publication Critical patent/WO2025014948A2/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F11/00—Compounds containing elements of Groups 6 or 16 of the Periodic Table

Definitions

  • Certain embodiments of the invention provide a method of converting a metathesis- inactive compound into a metathesis-active compound, comprising irradiating the metathesis- inactive compound with light.
  • Certain embodiments of the invention provide a method for converting a tungsten or molybdenum based ⁇ , ⁇ '-dialkyl metallacyclopentane compound into its metal-alkylidene isomer, comprising irradiating the ⁇ , ⁇ ’-dialkyl metallacyclopentane compound with light, wherein the ⁇ , ⁇ ’-dialkyl groups taken together with the ⁇ , ⁇ ’ carbons may optionally form a ring fused to the metallacyclopentane ring.
  • Certain embodiments of the invention provide a method for converting a tungsten or molybdenum based unsubstituted metallacyclopentane compound into a ⁇ , ⁇ ’-dialkyl metallacyclopentane compound.
  • Certain embodiments of the invention provide a compound of Formula II or Formula III wherein M is molybdenum (Mo) or tungsten (W); the two R groups are each independently alkyl, or the two R groups taken together with the intervening carbon atoms form a ring A, wherein one carbon atom of the ring A is optionally replaced with -(NRe)-; wherein the two R groups or the ring is each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; Z is O, or NR a ; X and Y are each independently ORb, N(Rc)2, or heteroaryl; Ra is alkyl, adamantyl, or aryl; R b is alkyl, aryl, or Si(R d ) 3 ; R c is alkyl, or aryl;
  • Certain embodiments of the invention provide a compound of Formula II, or Formula III. Certain embodiments of the invention provide one or more compounds of Formula II and/or Formula III, or mixture thereof. Certain embodiments of the invention provide a method for producing a catalyst compound of formula III or activating a compound of formula II, comprising irradiating the compound of formula II with light. Certain embodiments of the invention provide a catalyst compound or composition (e.g., metathesis compound or catalyst composition). Certain embodiments of the invention provide a method of catalyzing a metathesis reaction, comprising contacting one or more reactant compound (e.g., alkene) with a compound described herein, or a catalyst composition comprising one or more compound described herein. Certain embodiments of the invention provide a reaction as described herein.
  • reactant compound e.g., alkene
  • Certain embodiments of the invention provide a catalytic cycle, or step thereof, as described herein. Certain embodiments of the invention provide a compound (e.g., a complex, an adduct, or an intermediate) as described herein. Certain embodiments of the invention provide a method of making or using a compound, or a catalyst composition as described herein. Certain embodiments of the invention provide the use of a compound, or a catalyst composition for a metathesis reaction. Certain embodiments provide a compound as described herein. Certain embodiments provide a mixture as described herein. Certain embodiments provide a composition as described herein. Certain embodiments provide a method as described herein. The invention also provides processes and intermediates disclosed herein that are useful for preparing a compound or composition described herein.
  • a compound e.g., a complex, an adduct, or an intermediate
  • Certain embodiments of the invention provide a method of making or using a compound, or a catalyst composition as described herein.
  • Certain embodiments of the invention provide the use of a
  • FIGURES Figure 1. Molecular structure of square pyramidal trans-W( ⁇ , ⁇ '-Me 2 C 4 H 6 ). Ellipsoids are plotted at a 50% probability level. Hydrogen atoms, solvent molecules, and low occupancy disordered components are omitted for clarity. Figure 2. Eyring plot three rate constants at three temperatures for photolyses of W( ⁇ , ⁇ '- Me 2 C 4 H 6 ). Figure 3.
  • FIG 23 Partial proton NMR spectrum for Mo(NAr)(OSiPh3)2(trans-5,6-C8H14).
  • Figure 24 SCXRD of a mixture of co-crystallized Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) and Mo(NAr)(OSiPh 3 ) 2 (cis-5,6-C 8 H 14 ).
  • Figure 25 Alkylidenes obtained in solution through irradiation of Mo(NAr)(OSiPh3)2(5,6-C8H14).
  • Figure 26 SCXRD of syn-Mo(NAr)(OSiPh 3 ) 2 (trans-CHC 7 H 13 ).
  • Figure 27 Synthesis of compound having pyrrolide ligand.
  • Figure 28 Synthesis of compound having pyrrolide ligand.
  • Figure 29 Synthesis of compound having pyrrolide ligands.
  • Photoactivation a metal-alkylidene compound could be produced from a ⁇ ⁇ ⁇ ' disubstituted metallacyclopentane compound.
  • photoactivation of the ⁇ ⁇ ⁇ ' disubstituted compound into the metal-alkylidene compound may be primarily mediated through ⁇ hydrogen migration within metallacyclopentane.
  • a method for catalyzing metathesis reaction by contacting one or more reactant compound with a metathesis compound or composition described herein.
  • the metathesis catalyst composition may comprise a metathesis-active compound described herein and/or may comprise a metathesis-inactive compound that could be activated (e.g., via irradiation of light as described herein).
  • tungsten or molybdenum based ⁇ , ⁇ '- dialkyl metallacyclopentane compound and its metal-alkylidene isomer e.g., tungsten or molybdenum based ⁇ , ⁇ '- dialkyl metallacyclopentane compound and its metal-alkylidene isomer.
  • Metallacyclopentane ring is a 5-membered, MC4 ring.
  • the two carbon atoms immediately adjacent to M are ⁇ and ⁇ ' carbons, and the two carbon atoms second next to M are ⁇ , ⁇ ' carbon atoms.
  • the tungsten or molybdenum based metallacyclopentane compound described herein are disubstituted on ⁇ , ⁇ ' carbon atoms with two alkyl groups respectively.
  • the ⁇ , ⁇ '-dialkyl groups taken together with the ⁇ , ⁇ ' carbons may form a ring A that is fused to the metallacyclopentane ring, thus providing a bicyclic compound.
  • the tungsten or molybdenum based ⁇ , ⁇ '-dialkyl metallacyclopentane compound may be converted to its metal-alkylidene isomer as described herein.
  • Certain embodiments of the invention provide a compound of Formula I, Formula II, or Formula III wherein M is molybdenum (Mo) or tungsten (W); the two R groups are each independently alkyl (e.g., C 1 -C 16 or C 2 -C 8 ), or the two R groups taken together with the intervening carbon atoms form a ring A, wherein one carbon atom of the ring A is optionally replaced with -(NRe)-; wherein the two R groups or the ring is each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; Z is O, or NR a ; X and Y are each independently ORb, N(Rc)2, or heteroaryl; Ra is alkyl, adamantyl, or aryl; R b is alkyl, aryl,
  • Formula I, Formula II, or Formula III above are drawn in a manner that includes all of square pyramidal (SP), trigonal bipyramidal (TBP), syn, anti, cis, trans, or stereochemical isomers and possibilities.
  • the compound is a compound of Formula II, or Formula III.
  • the compound is a metathesis-active compound that could catalyze a metathesis reaction.
  • the compound is a metal-alkylidene compound.
  • the compound is a compound of Formula III.
  • the compound is a ⁇ ⁇ ⁇ ' disubstituted metallacyclopentane compound.
  • the compound is a compound of Formula II.
  • the compound is an unsubstituted metallacyclopentane compound.
  • the compound is a compound of Formula I.
  • illustrative examples of the two R groups and/or other groups (X, Y, Z, or M) in the compound of Formula I, Formula II, or Formula III are as follows.
  • M is tungsten (W).
  • M is molybdenum (Mo).
  • the compound of Formula I or Formula II may adopt a square pyramidal (SP) configuration.
  • the metallacyclopentane ring is disubstituted on ⁇ and ⁇ ' carbons.
  • the compound of Formual II is a trans- ⁇ ⁇ ⁇ ' disubstituted metallacyclopentane compound, wherein the two R groups are in trans- configuration.
  • the compound of Formual III is a trans- ⁇ ⁇ ⁇ ' disubstituted metal-alkylidene compound.
  • the compound of Formual II is a cis- ⁇ ⁇ ⁇ ' disubstituted metallacyclopentane compound, wherein the two R groups are in cis- configuration.
  • the compound of Formual III is a cis- ⁇ ⁇ ⁇ ' disubstituted metal-alkylidene compound.
  • the ⁇ ⁇ ⁇ ' carbons of the metal-alkylidene compound are carbon atoms that are second or third next to the metal atom.
  • the compound has structure of Formula IIa’: .
  • the compound has structure of Formula IIa’’: .
  • the compound has structure of Formula III anti .
  • the compound has structure of Formula III syn .
  • the compound has structure of Formula IIIa .
  • Formula IIIa above is drawn in a manner that is a syn metal-alkylidene compound.
  • the two R groups are each independently (C1-C16), (C2-C16), (C 3 -C 16 ), or (C 4 -C 16 ) alkyl.
  • the two R groups are each independently (C 1 -C 12 ), (C 2 -C 12 ), (C3-C12), or (C4-C12) alkyl. In certain embodiments, the two R groups are each independently (C1-C10), (C2-C10), (C 3 -C 10 ), or (C 4 -C 10 ) alkyl. In certain embodiments, the two R groups are each independently (C1-C8), (C2-C8), (C3- C8), or (C4-C8) alkyl. In certain embodiments, the two R groups are each independently (C 1 -C 6 ), (C 2 -C 6 ), (C 3 - C6), or (C4-C6) alkyl.
  • the two R groups are both methyl. In certain embodiments, the two R groups are not simultaneously methyl. In certain embodiments, the two R groups are each independently or both ethyl, propyl, butyl, pentyl, hexyl, heptanyl, or octanyl. In certain embodiments, the two R groups are each independently or both ethyl, 1- propyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptanyl, or 1-octanyl. In certain embodiments, the two R groups are both ethyl. In certain embodiments, the two R groups are each independently or both propyl (e.g., 1- propyl or isopropyl).
  • the two R groups are each independently or both butyl (e.g., 1- butyl or 2-butyl). In certain embodiments, the two R groups are each independently or both pentyl (e.g., 1- pentyl or neopentyl). In certain embodiments, the two R groups are each independently or both hexyl (e.g., 1- hexyl, or 2-hexyl). In certain embodiments, the two R groups are each independently or both heptanyl (e.g., 1-heptanyl, or 2-heptanyl). In certain embodiments, the two R groups are each independently or both octanyl (e.g., 1-octanyl, or 2-octanyl).
  • the two R groups are each independently unbranched alkyl. In certain embodiments, the two R groups are each independently branched alkyl. In certain embodiments, the two R groups as described herein are each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C 1 -C 6 ) alkyl.
  • the two R groups are each independently, optionally substituted with one or more aryl (e.g., phenyl). In certain embodiments, the two R groups are each independently, optionally substituted with one or more heteroaryl. In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkoxy (e.g., C 1 -C 6 alkoxy). In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkanoyl (e.g., C1-C6 alkanoyl). In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkoxycarbonyl (e.g., C 1 -C 6 alkoxycarbonyl).
  • aryl e.g., phenyl
  • the two R groups are each independently, optionally substituted with one or more heteroaryl.
  • the two R groups are each independently, optionally substituted with one or more alkoxy (e.g., C 1 -C 6
  • the two R groups are each independently, optionally substituted with one or more alkanoyloxy (e.g., C1-C6 alkanoyloxy).
  • the two R groups taken together with the intervening carbon atoms (i.e., ⁇ ⁇ ⁇ ' carbons), form a ring. Accordingly, in a compound of Formula II, the ring is fused to the metallacyclopentane to form a bicyclic compound.
  • the compound has structure of Formula IIb or Formula IIIb wherein the two R groups taken together with the intervening carbon atoms form a ring A that is optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl.
  • the compound has a structure of Formula IIb cis , wherein alpha and alpha’ carbon atoms of ring A are in cis configuration.
  • the compound has a structure of Formula IIbtrans, wherein alpha and alpha’ carbon atoms of ring A are in trans configuration.
  • the first carbon atom in ring A that is immediately next to the fused metallacyclopentane ring is alpha or alpha’ carbon atom of ring A
  • the second carbon atom in ring A is beta or beta’ carbon atom of ring A
  • the third carbon atom of ring A is gamma or gamma’ carbon atom of ring A.
  • the ring A is a 3, 4, 5, 6, 7, 8, 9, or 10-membered ring.
  • the ring A is a 5, or 6-membered ring.
  • the ring A is not a 5, or 6-membered ring. In certain embodiments, the ring A is a 3, or 4-membered ring. In certain embodiments, the ring A is a 7, 8, 9, or 10-membered ring. In certain embodiments, the ring A is a 7, or 8-membered ring. In certain embodiments, the ring A is a (C 3 -C 10 ) cycloalkane ring. In certain embodiments, the ring A is a (C3-C4) cycloalkane ring. In certain embodiments, the ring A is a (C 5 -C 6 ) cycloalkane ring.
  • the ring A is not a (C 5 -C 6 ) cycloalkane ring. In certain embodiments, the ring A is a (C7-C10) cycloalkane ring. In certain embodiments, the ring A is a (C8-C10) cycloalkane ring. In certain embodiments, the ring A is a (C 8 -C 9 ) cycloalkane ring. In certain embodiments, the ring A is a cyclopropane or cyclobutane ring. In certain embodiments, the ring A is a cyclopentane ring. In certain embodiments, the ring A is not a cyclopentane ring.
  • the ring A is a cyclohexane ring. In certain embodiments, the ring A is not a cyclohexane ring. In certain embodiments, the ring A is a cycloheptane ring. In certain embodiments, the ring A is a cyclooctane ring. In certain embodiments, the ring A is a cyclononane ring. In certain embodiments, the ring A is a cyclodecane ring.
  • the ring A is substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl.
  • one carbon atom of ring A is replaced with -(NRe)-.
  • a non-alpha carbon atom (e.g., beta carbon atom or gamma carbon atom) of ring A is replaced with -(NRe)-.
  • beta carbon atom of ring A is replaced with -(NRe)-.
  • the compound has structure of Formula IIb7 wherein X a is -CH 2 - or -NR e -.
  • the compound has structure of Formula IIb5 .
  • the compound is not a compound having structure of Formula IIb5.
  • the compound has structure of Formula IIb5′.
  • the compound is not a compound having structure of Formula IIb5′.
  • the compound has structure of Formula IIIb′ .
  • Formula IIIb’ above is drawn in a manner that is a syn- metal-alkylidene compound.
  • the ring A is cyclopentane. In certain embodiments, the ring A is not cyclopentane. In certain embodiments, the ring A is cyclohexane. In certain embodiments, the ring A is not cyclohexane. In certain embodiments, the compound is not a compound having structure of Formula IIIb′. In certain embodiments, wherein the compound has structure of Formula IIb6 or Formula IIb6′. . In certain embodiments, the compound is not a compound having structure of Formula IIb6 or Formula IIb6′.
  • Formula IIb, Formula IIb5, Formula IIb6, or Formula IIIb above are drawn in a manner that includes all of square pyramidal (SP), trigonal bipyramidal (TBP), syn, anti, cis, trans, or stereochemical isomers and possibilities.
  • the compound has structure of Formula IIIb anti or Formula IIIb syn .
  • the ring A is cyclopentane. In certain embodiments, the ring A is not cyclopentane. In certain embodiments, the ring A is cyclohexane. In certain embodiments, the ring A is not cyclohexane.
  • Z is O. In certain embodiments, Z is NR a .
  • Ra is aryl that is optionally substituted with one or more halo, hydroxy, amino, or (C 1 -C 6 ) alkyl (e.g., C 1 -C 4 alkyl).
  • R a is phenyl that is optionally substituted with one or more (C 1 -C 6 ) alkyl (e.g., isopropyl).
  • Ra is phenyl.
  • Ra is 2,6-diisopropylphenyl (2,6-i-Pr2C6H3).
  • Ra is pentafluorophenyl (-C6F5).
  • Ra is 2,6-dichlorophenyl.
  • R a is 2-Trifluoromethylphenyl.
  • Ra is alkyl (e.g., C1-C6 alkyl) that is optionally substituted with one or more halo, hydroxy, amino, aryl, or heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino.
  • R a is tBu.
  • Ra is methyl.
  • Ra is a methyl group substituted with one or more aryl, for example, Ra is triphenylmethyl (-C(Ph)3).
  • R a is adamantyl.
  • X and Y are each independently N(R c ) 2 . In certain embodiments, X and Y are each independently optionally substituted heteroaryl (e.g., 1-pyrrolyl, or 2,5-dimethyl-1-pyrrolyl). In certain embodiments, X and Y are each independently OR b , or N(R c ) 2 . In certain embodiments, X and Y are each independently ORb, or an optionally substituted heteroaryl (e.g., 1-pyrrolyl, or 2,5-dimethyl-1-pyrrolyl). In certain embodiments, X and Y are each independently OR b .
  • R b is alkyl (e.g., C1-C6 alkyl such as t-butyl) substituted with one or more halo (e.g., F). In certain embodiments, R b is C(CF 3 )(CH 3 ) 2 . In certain embodiments, R b is Si(R d ) 3 , wherein R d is aryl (e.g., phenyl) that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl (e.g., C1-C4 alkyl). In certain embodiments, X and Y are each OSi(Ph)3.
  • halo e.g., F
  • R b is C(CF 3 )(CH 3 ) 2 .
  • R b is Si(R d ) 3 , wherein R d is aryl (e.g., phenyl) that is optionally substituted with one or more halo,
  • X and Y are OSi(Ph) 3 and optionally substituted heteroaryl (e.g., 2,5-dimethyl-1-pyrrolyl). In certain embodiments, X and Y are each optionally substituted heteroaryl. In certain embodiments, X and Y are each pyrrole-based ligand (e.g., 2,5-dimethylpyrrole ligand). In certain embodiments, X and Y are each 2,5-dimethyl-1-pyrrolyl. In certain embodiments, X and Y are each OC(CF3)(CH3)2.
  • X and Y are optionally substituted heteroaryl (e.g., 2,5- dimethyl-1-pyrrolyl) and OC(CF 3 )(CH 3 ) 2 .
  • Rb is aryl that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl (e.g., C1-C4 alkyl).
  • Rb is phenyl that is optionally substituted with one or more (C1-C6) alkyl (e.g., C1-C4 alkyl).
  • R b is phenyl.
  • R b is alkyl (e.g., C 1 -C 8 alkyl) that is optionally substituted with one or more halo, hydroxy, amino, aryl, or heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino.
  • Rb is tBu.
  • R b is C(CF 3 )(CH 3 ) 2 , C(CF 3 ) 2 CH 3 , or C(CF 3 ) 3 .
  • Rc is aryl that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl.
  • Rc is phenyl that is optionally substituted with one or more alkyl (e.g., C 1 -C 4 alkyl). In certain embodiments, R c is phenyl. In certain embodiments, Rc is alkyl (e.g., C1-C8 alkyl) that is optionally substituted with one or more halo, hydroxy, amino, aryl, or heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino.
  • alkyl e.g., C1-C8 alkyl
  • aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino.
  • the compound having structure of Formula II is W(NCPh3)(OSiPh3)2( ⁇ , ⁇ '-Me2C4H6), or W(NCPh 3 )(OSiPh 3 ) 2 ( ⁇ , ⁇ '-Pent 2 C 4 H 6 ).
  • the compound having structure of Formula III is W(NCPh3)(OSiPh3)2(CHCH(Me)CHMe2), or W(NCPh 3 )(OSiPh 3 ) 2 (CHCH(Pent)CH(Pent)CH 3 ).
  • the compound having structure of Formula II is .
  • the compound having structure of Formula III is (including both syn and anti).
  • the compound having structure of Formula II is not . In certain embodiments, the compound having structure of Formula III is not (including both syn and anti). In certain embodiments, the compound having structure of Formula III is . In certain embodiments, the compound having structure of Formula III is not . In certain embodiments, the compound having structure of Formula II is In certain embodiments, the compound having structure of Formula III is (including both syn and anti). In certain embodiments, the compound having structure of Formula II is In certain embodiments, the compound having structure of Formula III is (including both syn and anti), or . In certain embodiments, the compound having structure of Formula II is , wherein Ar is 2,6-i-Pr 2 C 6 H 3 .
  • the compound having structure of Formula II is , wherein Ar is 2,6-i-Pr2C6H3.
  • the compound is Mo(NAr)(OSiPh 3 ) 2 (trans-5,6-C 8 H 14 ), , wherein Ar is 2,6-i-Pr 2 C 6 H 3 .
  • the compound having structure of Formula III is , (including both syn and anti) wherein Ar is 2,6-i-Pr 2 C 6 H 3 .
  • the compound having structure of Formula III is , (including both syn and anti) wherein Ar is 2,6-i-Pr 2 C 6 H 3 .
  • the compound is Mo(Nar)(OSiPh3)2(trans-CHC7H3), (including both syn and anti) wherein Ar is 2,6-i-Pr 2 C 6 H 3 .
  • the compound is syn-Mo(NAr)(OSiPh 3 ) 2 (trans-CHC 7 H 3 ).
  • the compound having structure of Formula II is , wherein R a is CPh 3, or optionally substituted aryl (e.g., 2,6-i-Pr 2 C 6 H 3 ).
  • Ra is 2,6-i-Pr2C6H3.
  • the compound having structure of Formula III is , (including both syn and anti) wherein RF 3 is C(CF 3 )(CH 3 ) 2 .
  • the compound having structure of Formula II is wherein R a is CPh 3, or optionally substituted aryl (e.g., 2,6-i-Pr 2 C 6 H 3 ).
  • Ra is 2,6-i-Pr2C6H3.
  • the compound having structure of Formula III is (structures including both syn and anti) wherein R a is CPh 3, or optionally substituted aryl (e.g., 2,6-i-Pr 2 C 6 H 3 ).
  • the compound having structure of Formula II or Formula III is a compound shown in Figures 4-11, wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound has structure of Formula II or Formula III, provided the compound is not a compound shown in Figures 4-11, wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound having structure of Formula II or Formula III is a compound of , , wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr 2 C 6 H 3 ).
  • the compound has structure of Formula II or Formula III, provided the compound is not a compound of wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr 2 C 6 H 3 ). In certain embodiments, the compound having structure of Formula III is not (including both syn and anti), or .
  • Certain embodiments of the invention provide a compound (e.g., a complex, an adduct, or an intermediate) described herein (also as described in Example 1).
  • Certain embodiments of the invention provide one or more compound (e.g., a catalyst compound), or mixture thereof, as described herein.
  • Certain embodiments of the invention provide one or more metathesis-active compound (e.g., a metathesis catalyst compound), or mixture thereof, as described herein.
  • Certain compound (e.g., a catalyst compound) described herein could be generated using the exemplary synthetic schemes described herein (also see Example 1 or Figures 4-11).
  • Catalyst Compositions Certain embodiments of the invention provide a catalyst composition comprising one or more compound(s) described herein (e.g., a compound of Formula III or Formula II).
  • the catalyst composition is a metathesis catalyst composition.
  • the catalyst composition could be activated with irradiation of light (e.g., blue light), for example, prior to catalyzing a metathesis reaction.
  • the catalyst composition could be activated or reactivated with irradiation of light prior to, during, and/or after a metathesis reaction.
  • the catalyst composition described herein encompasses initial catalyst composition (e.g., before the metathesis reaction begins) and also encompasses catalyst composition comprising a mixture of compounds formed during catalytic cycle(s) or in a reaction or method described herein.
  • the metathesis reaction may lead to the formation of metathesis-inactive compound, which may be reactivated, or converted to a metathesis-active compound by a method described herein.
  • the catalyst composition comprises a compound of Formula III as described herein.
  • the catalyst composition comprises a compound of Formula III as described herein and does not comprise a compound of Formula II as described herein.
  • the catalyst composition comprises a compound of Formula II as described herein.
  • the catalyst composition comprises a compound of Formula III as described herein and a compound of Formula II as described herein. In certain embodiments, the catalyst composition comprises a metathesis-active compound and a metathesis-inactive compound, wherein the metathesis-active compound is derived from the metathesis-inactive compound (e.g., via irradiation of light as described herein).
  • the catalyst composition comprises a compound of Formula III and a compound of Formula II, wherein the compound of Formula III is derived from the compound of Formula II (e.g., via irradiation of light as described herein); and the two R groups are each independently, optionally substituted alkyl as described herein; or the two R groups taken together with the intervening carbon atoms form a ring that is optionally substituted as described herein.
  • the catalyst composition comprises a compound of Formula IIIb and a compound of Formula IIb, wherein the compound of Formula IIIb is derived from the compound of Formula IIb (e.g., via irradiation of light as described herein).
  • the catalyst composition comprises a compound of Formula IIIa and a compound of Formula IIa’’, wherein the compound of Formula IIIa is derived from the compound of Formula IIa’’ (e.g., via irradiation of light as described herein).
  • the catalyst composition comprises two or more compounds described herein.
  • the catalyst composition comprises three or more compounds described herein.
  • the catalyst composition comprises four or more compounds described herein.
  • the catalyst composition comprises a compound having structure of Formula IIIsyn and a compound having structure of Formula IIIanti .
  • the catalyst composition comprises a compound having structure of Formula IIIsyn and a compound having structure of Formula IIIanti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.
  • the catalyst composition comprises a compound having structure of Formula IIIb syn and a compound having structure of Formula IIIb anti .
  • the catalyst composition comprises a compound having structure of Formula IIIb syn and a compound having structure of Formula IIIb anti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.
  • a catalyst composition described herein may comprise or further comprises a metal-alkylidene compound of formula V , wherein Z, M, X, Y, and the R group are as described above in Formula I, Formula II, or Formula III.
  • the compound of formula V is a metal-isopropylidene compound or wherein R is methyl.
  • the metal-isopropylidene compound is W(NCPh3)(OSiPh3)2(CMe2).
  • the compound of Formula III may be derived from the compound Formula II through metallacyclopentane alpha hydrogen migration process
  • the compound of formula V may be derived from the compound of Formula II through a metallacyclopentane ring contraction process.
  • a catalyst composition described herein may comprise a compound of Formula III and a compound of Formula V.
  • a catalyst composition described herein may comprise a compound of Formula III and a compound of Formula V at a ratio of about 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1. In certain embodiments, a catalyst composition described herein may comprise a compound of Formula III and a compound of Formula V at a ratio of about 4:1. In certain embodiments, a catalyst composition described herein may a compound of Formula III and a compound of Formula V at a ratio of about 10:1 to 2:1, or 8:1 to 3:1.
  • Certain embodiments of the invention provide a method for converting a tungsten or molybdenum based ⁇ , ⁇ '-dialkyl metallacyclopentane compound into its metal-alkylidene isomer, comprising irradiating the ⁇ , ⁇ ’-dialkyl metallacyclopentane compound with light, wherein the ⁇ , ⁇ ’-dialkyl groups taken together with the ⁇ , ⁇ ’ carbons may optionally form a ring A fused to the metallacyclopentane ring.
  • Certain embodiments of the invention provide a method for producing a catalyst compound of formula III, comprising irradiating a compound of formula II with light.
  • Certain embodiments of the invention provide a method for activating or converting a compound of formula II into a compound of formula III, comprising irradiating the compound of formula II with light.
  • the light comprises or consists of visible light.
  • the light comprises or consists of blue light.
  • the light comprises or consists of UV light.
  • the light comprises or consists of a wavelength range of about 260 to 750nm, or 380 to 750nm.
  • the light comprises or consists of a wavelength range of about 385-720nm, 390-600nm, 395-530nm, 400-525nm, 405-520nm, 405- 515nm, 405-510nm, 405 to 500nm, 410 to 490nm, or 420 to 480nm.
  • the light is blue light comprising or consisting of a wavelength range of about 380-500nm, 390-470nm, or 400-450nm.
  • the blue light comprises or consists of a wavelength of about 520, 510, 500, 490, 480, 470, 460, 450, 446, 445, 440, 430, 420, 410, 405, or 400nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 446, 445, or 405nm. In certain embodiments, the blue light comprises or consists of a wavelength of 405, 410, 420, 430, 440, 450, or 460nm.
  • the blue light comprises or consists of a wavelength that is less than about 520, 510, 500, 490, 480, 470, 460, 450, 445, 440, 430, 420, 410, 409, 408, 407, or 406nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 450, 445, 446, or 405nm. In certain embodiments, light irradiation is provided by a light source emitting a light spectrum that comprises or consists of a wavelength range described herein (e.g., about 380 to 750nm). In certain embodiments, light irradiation is provided using a narrow band light source such as LED or laser.
  • light irradiation is provided by a blue LED light source (e.g., 405nm, or 460nm). In certain embodiments, light irradiation is provided by a blue laser. In certain embodiments, light irradiation is provided by a light source as described herein (e.g., 405 ⁇ max or 445-446 nm ⁇ max LED light in Examples). As used herein, “blue light” refers to a light that comprises or consists of a wavelength range of 380-520nm or a portion thereof (e.g., 400-500nm, 445-450nm, 405-446nm, 405- 445nm, 445-446nm, or 404-406nm).
  • the light source may be a light bulb, tube, strip, or array of light sources.
  • the light source does not emit green, yellow, and/or red light.
  • the light source does not emit light with the wavelength range of about 530 to 750nm, 550 to 730nm, or 600 to 700nm.
  • light irradiation is provided using a broad band light source, e.g., that may emit a continuous spectrum of light, such as extending from UV to near infrared such as about 300-1400 nm.
  • the light is ambient light.
  • light irradiation is provided using an incandescent or fluorescent light source.
  • the light is sunlight.
  • the light comprises UV light comprising a wavelength range of about 280 to 380nm, 280 to 360nm, 280 to 315nm, 290 to 305nm, 290 to 300nm, 280 to 310nm, 315 to 360nm, or 315 to 380nm.
  • the light is UV light comprising or consisting of a wavelength range of about 280 to 380nm, 280 to 360nm, 280 to 315nm, 290 to 305nm, 280 to 310nm, 315 to 360nm, or 315 to 380nm.
  • the UV light comprises or consists of a wavelength of about 312nm.
  • light irradiation is provided by a UV light source (e.g., UV lamp).
  • the light source brightness and/or wattage may vary to suit the requirements of reactions at different scales.
  • the light source may have a wattage of about 1, 10, 50, 100, 200, 400, 600, or 800mW.
  • the light source may have a wattage of about 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000W, or higher.
  • the light source may have a wattage of about 1mW to 2000W, 60mW to 600W, or 100mW to 400W.
  • the light source may have a brightness of about 1 to 100,000, 10 to 10,000, 100 to 3000, or 1000 to 5000 lumens.
  • the compound of formula II is irradiated with light without heating (e.g., at room temperature such as at about 20-25 °C).
  • the compound of formula II is irradiated with light with cooling at a temperature that is lower than room temperature.
  • the compound of formula II is irradiated with light at a temperature that is lower than 20, 15, 10, 5, 0, -5, -10, -20, -30, -40, -50, -60, -70, -80, -90, or -100°C.
  • the compound of formula II is irradiated with light at a temperature that is lower than -40, -50, -60, -70, -80, -90, or -100°C. In certain embodiments, the compound of formula II is irradiated with light at about 5- 20°C. In certain embodiments, the compound of formula II is irradiated with light at about 0- 4°C. In certain embodiments, the compound of formula II is irradiated with light at about 0 to - 90°C, -10 to -85°C, -20 to -80°C.
  • the compound of formula II is irradiated with light at about -10, -20, -30, -40, -50, -60, -70, -80, or -90°C. In certain embodiments, the compound of formula II is irradiated with light at about -30 or -80°C. In certain embodiments, the compound of formula II is irradiated with light at about -40 to -90°C, -45 to -85°C, -50 to -80°C. In certain embodiments, the compound of formula II is irradiated with light with heating (e.g., to a temperature that is above room temperature).
  • the compound of formula II is irradiated with light at about 30-50°C, or 35-45°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is about 30, 35, 40, 45, or 50°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is at least about 30, 35, 40, 45, or 50°C.
  • light irradiation in particular, at high power
  • close proximity with a light source may convey heat
  • heating as used herein only refers to temperature control provided by a temperature control apparatus or a heating source other than the light source.
  • the compound of formula II is irradiated with light for about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23hrs, 1 day, 2 days, or longer. In certain embodiments, the compound of formula II is irradiated with light for about 0.5-16hrs, 1-12hrs, 1-9hrs, 1.5-8hrs, 2-6hrs, or 2-4hrs. In certain embodiments, the compound of formula II is irradiated with light for about 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 hrs.
  • the methods described herein may produce a compound having structure of Formula III syn and a compound having structure of Formula III anti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.
  • the methods described herein may produce a compound having structure of Formula IIIb syn and a compound having structure of Formula IIIb anti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.
  • the produced compound of formula III is a compound described herein (e.g., as described above, or in Example 1, or in Figures).
  • the produced compound of formula III the compound is not a compound of wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
  • the compound of Formula III is produced in a reaction condition that is free of acid or in the absence of proton (e.g., in a solution free of acid or proton).
  • the method for producing compound of Formula III (or activating compound of Formula II) may further produce a metallacyclopentane ring contraction product, or a metal-alkylidene compound of formula V , wherein Z, M, X, Y, and the R group are as described above in Formula I, Formula II, or Formula III.
  • the compound of formula V is a metal-isopropylidene compound or wherein R is methyl.
  • the metal-alkylidene compound is W(NCPh 3 )(OSiPh 3 ) 2 (CMe 2 ).
  • the compound of Formula III may be derived from the compound Formula II through metallacyclopentane alpha hydrogen migration process
  • the compound of formula V may be derived from the compound of Formula II through a metallacyclopentane ring contraction process.
  • a compound of Formula III and a compound of Formula V are produced at a ratio of about 10:1, 9:1, 8:1, 6:1, 5:1, 4:1, 3:1, or 2:1.
  • a compound of Formula III and a compound of Formula V are produced at a ratio of about 4:1.
  • a compound of Formula III and a compound of Formula V are produced at a ratio of about 10:1 to 2:1, or 8:1 to 3:1.
  • a compound of Formula V may be produced when irradiation of light on compound of Formula II is conducted without cooling.
  • a compound of Formula V may be produced when irradiation of light on compound of Formula II is conducted with heating.
  • a compound of Formula V is produced when irradiation of light on compound of Formula II is conducted at a temperature of about 15-35°C, 20-30°C, or 22-25°C.
  • a compound of Formula V is produced when irradiation of light on compound of Formula II is conducted at about room temperature.
  • the method for producing a catalyst compound of formula III further comprises producing compound of formula II by contacting a compound of Formula I with an alkene compound.
  • certain embodiments of the invention provide a method of producing compound of formula II by contacting a compound of Formula I with an alkene compound.
  • the alkene compound is C 3 -C 18 , C 4 -C 18 , or C 5 -C 18 alkene.
  • the alkene compound is C 3 -C 16 , C 4 -C 16 , or C 5 -C 16 alkene. In certain embodiments, the alkene compound is C3-C14, C4-C14, or C5-C14 alkene. In certain embodiments, the alkene compound is C3-C12, C4-C12, or C5-C12 alkene. In certain embodiments, the alkene compound is C 3 -C 10 , C 4 -C 10 , or C 5 -C 10 alkene. In certain embodiments, the alkene compound is C3-C8, C4-C8, or C5-C8 alkene.
  • the alkene compound is C3-C7, C4-C7, or C5-C7 alkene. In certain embodiments, the alkene compound is C 3 -C 6 , C 4 -C 6 , or C 5 -C 6 alkene. In certain embodiments, the alkene compound is propene. In certain embodiments, the alkene compound is not propene. In certain embodiments, the alkene compound is 1-butene. In certain embodiments, the alkene compound is 1-pentene. In certain embodiments, the alkene compound is 1-hexene. In certain embodiments, the alkene compound is 1-heptene. In certain embodiments, the alkene compound is 1-octene.
  • the alkene compound is 1-nonene. In certain embodiments, the alkene compound is 1-decene. In certain embodiments, the alkene compound is 1,4-pentadiene. In certain embodiments, the alkene compound is 1,5-hexadiene. In certain embodiments, the alkene compound is 1,6-heptadiene. In certain embodiments, the alkene compound is not 1,6-heptadiene. In certain embodiments, the alkene compound is 1,7-octadiene. In certain embodiments, the alkene compound is not 1,7-octadiene. In certain embodiments, the alkene compound is 1,8-nonadiene.
  • the alkene compound is 1,9-decadiene.
  • the alkene compound is substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl.
  • the alkene compound is N,N-Diallylaniline.
  • the alkene compound is Diallylamine.
  • the alkene compound is Diallyl-methyl-amine or Diallyl-ethyl-amine. In certain embodiments, the alkene compound is N,N-Di(3-butenyl)aniline. In certain embodiments, the alkene compound is dissolved in organic solution for contacting a compound of Formula I. In certain embodiments, a gaseous alkene compound is supplied (e.g., under about 1 atmospheric pressure) for contacting a compound of Formula I. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted in the dark.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of about 70-110°C, 73-100°C, 75-95°C, 78-90°C, or 80-88°C. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of about 90-110°C, 90-105°C, 90-95°C, or 95-100°C.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of about, or at least about, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90°C.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of at least about, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100°C.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted without heating (e.g., at about room temperature of about 20-25°C). In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted for about 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23hrs, 1 day, 2 days, or longer. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted for about 1-24hrs, 1-16hrs, 1-12hrs, 1-8hrs, 2-6hrs, or 2- 3hrs.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) further comprises removing volatile material (e.g., ethylene and/or organic solvent such as toluene). In certain embodiments, removing volatile material comprises applying vacuum.
  • volatile material e.g., ethylene and/or organic solvent such as toluene.
  • the producing compound of formula II comprises step a), and one or more step of b), c), d) and e): a) contacting a compound of formula I with an alkene compound, b) preventing light exposure (prior to, or during the contacting), c) heating to a temperature as described herein (e.g., 70-100°C), d) removing volatile material, and e) dissolving residue in organic solvent (e.g., toluene).
  • the producing compound of formula II comprising steps a), b), c), d), and/or e) is one round of reaction, which could be repeated for two or more times.
  • alkene compound is supplied and after a period of reaction (e.g., 2-3hrs or as described herein) volatile material is removed, overall, to improve yield, purity or drive complete conversion of a compound of formula I to the beta, beta’-disubstituted compound of Formula II.
  • a period of reaction e.g. 2-3hrs or as described herein
  • volatile material is removed, overall, to improve yield, purity or drive complete conversion of a compound of formula I to the beta, beta’-disubstituted compound of Formula II.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) could be conducted in the dark with heating at about 80-85°C for about 2-6hrs or 2-12hrs, followed by applying vacuum to remove volatile material and redissolving residues in organic solvent. This process could be repeated for two or three times or more.
  • the produced compound of formula II the compound is a compound described herein (e.g., as described above, or in Example 1, or in Figures).
  • the methods described herein may produce a mixture comprising a compound of Formula IIb cis and a compound of Formula IIb trans at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:3, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.
  • the methods described herein may produce a mixture comprising a compound of Formula IIb cis and a compound of Formula IIb trans at a ratio of about 7:3.
  • the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) further comprises heating a mixture (e.g., at 45-55°C, such as 50 °C) for 2-48hrs (e.g., 12-36hrs, or 24hrs) to generate an equilibrium mixture.
  • an equilibrium mixture comprises a compound of Formula IIbcis and a compound of Formula IIbtrans at a ratio of about1:6, 1:7, 1:8, or 3:22.
  • the produced compound of formula II the compound is not a compound of wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
  • the method for producing a compound of formula III and/or formula II further comprises firstly producing compound of formula I by contacting a metal- dichloride compound of formula IV with ethylene and/or ethyl-metal (e.g., Et2Zn or EtMgBr) as described herein , wherein Z, M, X, and Y are as described in Formula I, Formula II, or Formula III.
  • Certain embodiments of the invention provide a method for catalyzing a metathesis reaction, comprising contacting one or more reactant compounds with a catalyst compound or composition described herein (e.g., a compound of Formula III and/or a compound of Formula II).
  • the method for catalyzing a metathesis reaction comprises contacting one or more reactant compounds with a compound of Formula III.
  • the method for catalyzing a metathesis reaction comprises contacting one or more reactant compounds with a compound of Formula II.
  • the method for catalyzing a metathesis reaction further comprises activating or converting a compound of Formula II into a compound of Formula III.
  • the method for catalyzing a metathesis reaction further comprises irradiating the catalyst compound or composition with light.
  • the method further comprises irradiating the catalyst compound or composition with light prior to contacting one or more reactant compounds with the catalyst described herein (e.g., a compound of Formula III and/or a compound of Formula II).
  • the method further comprises irradiating the catalyst compound or composition with light after contacting one or more reactant compounds with the catalyst described herein (e.g., a compound of Formula III and/or a compound of Formula II).
  • the light comprises or consists of visible light.
  • the light comprises or consists of blue light.
  • the light comprises or consists of a wavelength range of about 380 to 750nm. In certain embodiments, the light comprises or consists of a wavelength range of about 385-720nm, 390-600nm, 395-530nm, 400-525nm, 405-520nm, 405-515nm, 405-510nm, 405 to 500nm, 410 to 490nm, or 420 to 480nm. In certain embodiments, the light is blue light comprising or consisting of a wavelength range of about 380-500nm, 390-470nm, or 400-450nm.
  • the blue light comprises or consists of a wavelength of about 520, 510, 500, 490, 480, 470, 460, 450, 445, 440, 430, 420, 410, 405, or 400nm. In certain embodiments, the blue light comprises or consists of a wavelength of 405, 410, 420, 430, 440, 450, or 460nm. In certain embodiments, the blue light comprises or consists of a wavelength that is less than about 520, 510, 500, 490, 480, 470, 460, 450, 445, 440, 430, 420, 410, 409, 408, 407, or 406nm.
  • the blue light comprises or consists of a wavelength of about 450, or 405nm.
  • light irradiation is provided by a light source emitting a light spectrum that comprises or consists of a wavelength range described herein (e.g., about 380 to 750nm).
  • light irradiation is provided using a narrow band light source such as LED or laser.
  • light irradiation is provided by a blue LED light source (e.g., 405nm, or 460nm).
  • light irradiation is provided by a blue laser.
  • the light source may be a light bulb, tube, strip, or array of light sources.
  • the light source does not emit green, yellow, and/or red light.
  • the light source does not emit light with the wavelength range of about 530 to 750nm, 550 to 730nm, or 600 to 700nm.
  • light irradiation is provided using a broad band light source, e.g., that may emit a continuous spectrum of light, such as extending from UV to near infrared such as about 300-1400 nm.
  • the light is ambient light.
  • light irradiation is provided using an incandescent or fluorescent light source.
  • the light is sunlight.
  • the light source brightness and/or wattage may vary to suit the requirements of reactions at different scales.
  • the light source may have a wattage of about 1, 10, 50, 100, 200, 400, 600, 800mW, or 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000W, or higher.
  • the light source may have a wattage of about 1mW to 2000W, 60mW to 600W, or 100mW to 400W.
  • the light source may have a brightness of about 1 to 100,000, 10 to 10,000, 100 to 3000, or 1000 to 5000 lumens.
  • the compound of formula II is irradiated with light without heating (e.g., at room temperature such as at about 20-25 °C). In certain embodiments, the compound of formula II is irradiated with light with cooling at a temperature that is lower than room temperature. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is lower than 20, 15, 10, 5, 0, -5, -10, -20, -30, -40, -50, -60, -70, -80, -90, or -100°C.
  • the compound of formula II is irradiated with light at a temperature that is lower than -40, -50, -60, -70, -80, -90, or -100°C. In certain embodiments, the compound of formula II is irradiated with light at about 5- 20°C. In certain embodiments, the compound of formula II is irradiated with light at about 0- 4°C. In certain embodiments, the compound of formula II is irradiated with light at about 0 to - 90°C, -10 to -85°C, -20 to -80°C.
  • the compound of formula II is irradiated with light at about -10, -20, -30, -40, -50, -60, -70, -80, or -90°C. In certain embodiments, the compound of formula II is irradiated with light at about -30 or -80°C. In certain embodiments, the compound of formula II is irradiated with light at about -40 to -90°C, -45 to -85°C, -50 to -80°C. In certain embodiments, the compound of formula II is irradiated with light with heating (e.g., to a temperature that is above room temperature).
  • the compound of formula II is irradiated with light at about 30-50°C, or 35-45°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is about 30, 35, 40, 45, or 50°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is at least about 30, 35, 40, 45, or 50°C.
  • light irradiation in particular, at high power
  • close proximity with a light source may convey heat
  • heating as used herein only refers to temperature control provided by a temperature control apparatus or a heating source other than the light source.
  • the compound of formula II is irradiated with light for about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23hrs, 1 day, 2 days, or longer. In certain embodiments, the compound of formula II is irradiated with light for about 0.5-16hrs, 1-12hrs, 1-9hrs, 1.5-8hrs, 2-6hrs, or 2-4hrs. In certain embodiments, the compound of formula II is irradiated with light for about 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 hrs. Methods for catalyzing metathesis reaction are known in the art and described herein.
  • one reactant compound is contacted with the catalyst composition.
  • two different reactant compounds i.e., a first reactant compound and a second reactant compound
  • a reactant compound is an alkene compound.
  • a reactant compound is a cyclic alkene (cycloalkene).
  • the one or more reactant compounds are alkene compounds.
  • the alkene compound is a C 2 -C 20 alkene compound. In certain embodiments, the reactant alkene compound is a C 2 -C 18 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C16 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C14 alkene compound. In certain embodiments, the reactant alkene compound is a C 2 -C 12 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C10 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C8 alkene group.
  • unsaturated fatty acid e.g., monounsaturated or polyunsaturated C3-C26
  • the reactant compound is an unsaturated C4-C24 or C6-C22 fatty acid or ester thereof. In certain embodiments, the reactant compound is an unsaturated C 8 -C 20 or C 10 -C 18 fatty acid or ester thereof.
  • the method for catalyzing a metathesis reaction is conducted in the dark. In certain embodiments, the method for catalyzing a metathesis reaction is conducted with irradiation of light. In certain embodiments, the method for catalyzing a metathesis reaction further comprises heating the catalyst composition. In certain embodiments, the method further comprises heating the catalyst composition to a temperature that is higher than about 25 °C.
  • the method for catalyzing a metathesis reaction further comprises heating the catalyst composition to about 30 ⁇ 130 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 40 ⁇ 120 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 50 ⁇ 110 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 60 ⁇ 105 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 70 ⁇ 100 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 80 ⁇ 90 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 50 to 150 o C, 60 to 140 o C, 70 to 130 o C, or 80 to 120 o C.
  • the method for catalyzing a metathesis reaction further comprises heating to at least about 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 o C. In certain embodiments, the method further comprises heating to about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 o C. In certain embodiments, the method for catalyzing a metathesis reaction is conducted for at least 5, 10, 15, 30, 45 minutes, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 36h, 48h, 72h or longer.
  • metathesis reaction is described herein and known in the art and is given its ordinary meaning in the art and refers to a chemical reaction in which two reacting species exchange partners.
  • a metathesis reaction is performed in the presence of a transition-metal catalyst.
  • a byproduct of a metathesis reaction may be ethylene.
  • a metathesis reaction may involve reaction between species comprising, for example, olefins and/or alkynes. Examples of different kinds of metathesis reactions include cross metathesis, ring-closing metathesis, ring-opening metathesis, acyclic diene metathesis, alkyne metathesis, enyne metathesis, olefin metathesis and the like.
  • a metathesis reaction may occur between two substrates which are not joined by a bond (e.g., intermolecular metathesis reaction) or between two portions of a single substrate (e.g., intramolecular metathesis reaction).
  • two substrates of a metathesis reaction are identical.
  • a metathesis reaction is an ethenolysis reaction.
  • alkyl by itself or as part of another substituent, means, unless otherwise stated, a straight or branched chain hydrocarbon radical, having the number of carbon atoms designated (i.e., C1-8 means one to eight carbons).
  • Examples include (C1-C8)alkyl, (C2-C8)alkyl, (C1-C6)alkyl, (C2-C6)alkyl, (C1-C3)alkyl, and (C3-C6)alkyl.
  • alkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, iso-butyl, sec-butyl, n-pentyl, n-hexyl, n- heptyl, n-octyl, and higher homologs and isomers.
  • aryl refers to a single all carbon aromatic ring or a multiple condensed all carbon ring system wherein at least one of the rings is aromatic.
  • an aryl group has 6 to 20 carbon atoms, 6 to 14 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms.
  • Aryl includes a phenyl radical.
  • Aryl also includes multiple condensed carbon ring systems (e.g., ring systems comprising 2, 3 or 4 rings) having about 9 to 20 carbon atoms in which at least one ring is aromatic and wherein the other rings may be aromatic or not aromatic (i.e., cycloalkyl.
  • the rings of the multiple condensed ring system can be connected to each other via fused, spiro and bridged bonds when allowed by valency requirements. It is to be understood that the point of attachment of a multiple condensed ring system, as defined above, can be at any position of the ring system including an aromatic or a cycloalkyl portion of the ring.
  • aryl groups include, but are not limited to, phenyl, indenyl, indanyl, naphthyl, 1, 2, 3, 4-tetrahydronaphthyl, anthracenyl, and the like.
  • halo or “halogen” refers to bromo, chloro, fluoro or iodo.
  • halogen refers to chloro or fluoro.
  • heteroaryl refers to a single aromatic ring that has at least one atom other than carbon in the ring, wherein the atom is selected from the group consisting of oxygen, nitrogen and sulfur; “heteroaryl” also includes multiple condensed ring systems that have at least one such aromatic ring, which multiple condensed ring systems are further described below.
  • heteroaryl includes single aromatic rings of from about 1 to 6 carbon atoms and about 1-4 heteroatoms selected from the group consisting of oxygen, nitrogen and sulfur. The sulfur and nitrogen atoms may also be present in an oxidized form provided the ring is aromatic.
  • heteroaryl ring systems include but are not limited to pyridyl, pyrimidinyl, oxazolyl or furyl.
  • “Heteroaryl” also includes multiple condensed ring systems (e.g., ring systems comprising 2, 3 or 4 rings) wherein a heteroaryl group, as defined above, is condensed with one or more rings selected from cycloalkyl, aryl, heterocycle, and heteroaryl. It is to be understood that the point of attachment for a heteroaryl or heteroaryl multiple condensed ring system can be at any suitable atom of the heteroaryl or heteroaryl multiple condensed ring system including a carbon atom and a heteroatom (e.g., a nitrogen).
  • heteroaryls include but are not limited to pyridyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrazolyl, thienyl, indolyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, furyl, oxadiazolyl, thiadiazolyl, quinolyl, isoquinolyl, benzothiazolyl, benzoxazolyl, indazolyl, quinoxalyl, and quinazolyl.
  • heteroatom is meant to include oxygen (O), nitrogen (N), sulfur (S) and silicon (Si).
  • O oxygen
  • N nitrogen
  • S sulfur
  • Si silicon
  • Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., "Stereochemistry of Organic Compounds", John Wiley & Sons, Inc., New York, 1994.
  • the compounds of the invention can contain asymmetric or chiral centers, and therefore exist in different stereoisomeric forms.
  • a compound prefixed with (+) or d is dextrorotatory.
  • these stereoisomers are identical except that they are mirror images of one another.
  • a specific stereoisomer can also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture.
  • a 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which can occur where there has been no stereoselection or stereospecificity in a chemical reaction or process.
  • the terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity.
  • Example 1 When a bond in a compound formula herein is drawn in a non-stereochemical manner (e.g. flat), the atom to which the bond is attached includes all stereochemical possibilities. Certain embodiments of the invention will be illustrated in the following non-limiting Example. Example 1.
  • W( ⁇ , ⁇ '-Me2C4H6) is consumed in a first order manner upon photolysis at 405 nm and 243 K to give primarily an alkylidene formed through ⁇ hydrogen abstraction.
  • ⁇ 20% of an isopropylidene complex is also formed through ring-contraction to give a ⁇ , ⁇ , ⁇ -trimethyltungstacyclobutane which loses propylene.
  • a bicylic tungstacyclopentane complex - prepared by treating W(NCPh3)Cl2(OSiPh3)2 with two equivalents of BrMg(CH 2 ) 5 CHCH 2 - undergoes ⁇ 95% ⁇ hydrogen abstraction upon photolysis, while a ⁇ , ⁇ '-dipentyl tungstacyclopentane complex undergoes ⁇ 87% ⁇ hydrogen abstraction upon photolysis.
  • An Eyring plot for consumption of W( ⁇ , ⁇ '-Me2C4H6) reveals that the apparent activation energy of only ⁇ 2.3 kcal mol -1 .
  • SP square pyramidal
  • W(C 4 H 8 ) complexes are thermally stable in solution in the dark, but under visible light the five-membered ring contracts to give a SP ⁇ methyl- substituted tungstacyclobutane complex (W( ⁇ -MeC3H5), eq 1), 5 the trigonal bipyramidal (TBP) form of which is the key intermediate in olefin metathesis reactions.
  • Single crystal X-ray structural analysis (Fig 1) shows its geometrical parameters to be comparable to those of the unsubstituted SP complex, 5 W(C 4 H 8 ), except the W-C bond lengths in W( ⁇ , ⁇ '-Me 2 C 4 H 6 ) (2.173, 2.163) are slightly shorter than those in W(C 4 H 8 ) (2.222, 2.202) (>95% probability on the basis of +/- 3 ⁇ ).
  • the rate of disappearance of W( ⁇ , ⁇ '-Me2C4H6) is about half the rate of disappearance of W(C4H8) in the same photochemical reactor under identical conditions (Table 1).
  • Table 1 Photolyses at 405 nm and 298 K in toluene-d8.
  • the fastest subsequent step in W(C 4 H 8 ) is a shift of a hydrogen atom from a ⁇ -CH 2 to the CH 2 group next to it in the W(C 4 H 8 ) ring, concurrent with formation of a W-C bond to give an ⁇ -methyl-W(VI) tungstacyclobutane, W( ⁇ -MeC3H5). Because 1,2-hydrogen atom shifts in free hydrocarbon radicals have prohibitively high barriers, 16 this "ring-contraction" must be “assisted" by the metal through CH agostic interactions.
  • Tetrahydrofuran, diethyl ether, dichloromethane, and toluene were dried and deoxygenated by argon purge followed by passage through activated alumina in a solvent purification system followed by storage over 4 ⁇ molecular sieves.
  • Non-halogenated and non-nitrile containing solvents were tested with a standard purple solution of sodium benzophenone ketyl in THF to confirm effective oxygen and moisture removal prior to use.
  • W(NCPh 3 )(OSiPh 3 ) 2 (C 4 H 8 ) [1] was prepared according to the published procedure.
  • Ethylene Ultra High Purity was used as received from Airgas. Elemental analyses were performed at Atlantic Microlab, Inc., Norcross, GA.
  • Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc., degassed, and dried over activated 4 ⁇ molecular sieves for at least 24 h prior to use.
  • NMR spectra were recorded on Bruker Avance 600 MHz, Bruker Avance 500 MHz and Bruker Avance 300 MHz spectrometers.
  • 1 H and 13 C chemical shifts are reported in ppm relative to tetramethylsilane using residual solvent as an internal standard.
  • 19 F and 31 P chemical shifts are reported in ppm relative to respectively fluorobenzene and H 3 PO 4 as external standards.
  • Irradiations with Blue LEDs were realized with 30 Blue 5050 SMD (nominal power 3.1 mW, on a strip), powered by a 12V DC power supply and with an inline DC dimmer.
  • the fluorescent tube installed in the laboratory is Sylvania FO32/835/ECO.
  • Emission spectra were measured with the spectrometer OceanOptics USB4000.
  • UV/Vis spectra were recorded using a Cary 60 Agilent spectrophotometer.
  • the mixture was degassed (2 freeze-pump-thaw cycles) and resubmitted to the reaction conditions. Removal of volatiles and resubmission to the reaction conditions as described was repeated until monitoring of the reaction progress by 1 H NMR spectroscopy showed complete conversion of starting material and intermediates.
  • the volatiles were removed in vacuo and the crude product was recrystallized from toluene at room temperature to obtain the title compound (190 mg, 0.162 mmol, 67% from two crops) as brown crystals.
  • Single crystal X-ray structural analysis revealed excessive twinning in the sample and a significant degree of disorder mostly concerning the pentyl substituents of the Pent2C4H6 fragment. Anal.
  • a yellow crystal (block, approximate dimensions 0.39 ⁇ 0.23 ⁇ 0.17 mm 3 ) was placed onto the tip of a MiTeGen pin and mounted on a Bruker Venture D8 diffractometer equipped with a PhotonIII detector at 180.00 K.
  • a collection strategy was calculated and complete data to a resolution of 0.82 ⁇ with a redundancy of 5.9 were collected. Three major twin domains were identified.
  • the frames were integrated with the Bruker SAINT [9] software package using a narrow-frame algorithm to 0.82 ⁇ resolution.
  • the bicyclic complexes can be prepared "directly" from the dialkoxide dichloride complexes without isolating any tungstacyclopentane intermediate using diethyl zinc as the reducing agent in the presence of 1,6-heptadiene or 1,7-octadiene.
  • An analog of a 7-tungstabicylo[3.3.0]octane complex can be prepared from diallylaniline. Eight tungstacyclopentanes and one alkylidene derived through photolysis of a 7-tungstabicylo[4.3.0]nonane complex were characterized through single crystal X-ray diffraction studies.
  • ⁇ ⁇ ⁇ '-disubstituted tungstacyclopentane complexes can be formed from terminal olefins and that they rearrange in the absence of acid to alkylidenes through a photo-induced ring-contraction or (predominantly) ⁇ hydrogen abstraction, each of which is proposed to be assisted through CH agostic reactions in the ground or excited state of the 14e tungstacyclopentane complexes.
  • the proton NMR spectrum of 1 shows two resonances for the tungstacyclopentane protons at 298 K, but four resonances at 235 K (Fig 13), consistent with interconversion of “up” and “down” ⁇ protons and “up” and “down” ⁇ protons in a square pyramidal complex through an intramolecular five- coordinate Berry-type rearrangement via an intermediate that contains a plane of symmetry passing through the carbon atoms in a WC 4 ring (on average).
  • Compounds 2a and 2b can also be prepared through addition of one equivalent of diethylzinc to W(NPh)(OR F3 ) 2 Cl 2 (THF) or W(NAr)(OR F3 ) 2 Cl 2 (THF) under ethylene (eq 2).
  • Diethylzinc is potentially more desirable than EtMgBr because the risk of “overalkylation” to give complexes that contain more than two ethyl groups is lower. Diethylzinc is also relatively cheap and potentially complicating chloride/bromide is avoided.
  • the W-C ⁇ bond lengths are 2.177(9) and 2.182(9) ⁇ , which are typical of W(VI)-C bonds in compounds of this type.
  • the H ⁇ resonance is found at 2.73 ppm in proton NMR spectra and the C ⁇ at 77.2 ppm in 13 C NMR spectra.
  • Compound 3 also can be prepared from W(NAr)(OsiPh3)2Cl2 under dinitrogen using diethylzinc in place of the Grignard reagent without isolating any intermediate; the yield is typically 84% yield on a 300 mg scale (eq 4).
  • the H ⁇ resonances are found at 2.94, 2.67, and 2.27 ppm in proton NMR spectra.
  • W(NAr)(OR F3 ) 2 (C 8 H 14 ) (5; eq 5) can be prepared from W(NAr)(OR F3 ) 2 Cl 2 , diethylzinc, and 1,7-octadiene in a manner similar to syntheses shown in equations 4 and 5 and isolated in 78% yield.
  • the phenylimido variation of 5, W(NPh)(ORF3)2(cis-C8H14) (6a), is also prepared readily, but it was found to have a cis ring junction with the C 6 ring pointing down and away from the phenylimido ligand (Fig 18).
  • NMR spectra of a sample of W(NPh)(ORF3)2(C8H14) in solution was found to be a mixture that contained 70% of the cis isomer (6a) and 30% of the trans isomer (6b).
  • Ring-down and “ring-up” isomers can also interconvert, but on a faster time-scale of the order of a typical pseudorotation process. For example, a small amount (5-10%) of the ring-up isomer of W(NAr)(OSiPh3)2(C7H12) is found in a solution of the ring-down isomer in toluene-d8 at 238 K. At 298 K these minor resonances begin to broaden, consistent with interconversion of the ring-up and ring-down isomers through a pseudorotation process that is related to interconversion of up and down protons in W(NPh)(OSiPh3)2(C4H8), for example (Fig.13).
  • diallylaniline reacts with W(NAr)(OSiPh 3 ) 2 (C 4 H 8 ) to form a tungstabicyclic compound, W(NAr)(OSiPh3)2(C6H10NPh) (8; eq 7), analogous to W(NAr)(OSiPh 3 ) 2 (C 7 H 12 ) (3).
  • the 1 H and 13 C NMR features of W(C6H10NPh) are similar to those of 3.
  • the weak low energy tails in these absorptions extend to 450 nm and overlap with the 450 nm LED light emission (half height width ⁇ 30 nm ).
  • 4 Irradiation of W(NPh)(OSiPh 3 ) 2 (C 4 H 8 ) (1) in toluene-d 8 with blue LEDs ( ⁇ Max 446 nm, ⁇ 93 mW power) under ethylene, was followed by 1 H NMR for 30 min and gave a >90% conversion of 1 to propylene and W(NPh)(OSiPh3)2(C3H6) (13).
  • the W(NPh)(OSiPh 3 ) 2 (C 3 H 6 ) complex that is formed is a mixture of TBP and SP forms, according to proton and 13 C NMR studies, with the TBP form predominating ( ⁇ 90%).
  • the characteristic resonances for the TBP form are found at 98.70 ppm (C ⁇ of TBP isomer) and -4.40 ppm (C ⁇ of TBP isomer), while the SP resonances are found at 45.31 ppm (C ⁇ of SP isomer) and 22.92 ppm (C ⁇ of SP isomer; Table A1).
  • s olvent k (10-4 s-1) W(NPh)(OSiPh3)2(C4H8) (1) tol-d8 35 W(NPh)(OSiPh3)2(C4H8) (1) thf-d8 10 W(NAr)(OSiPh 3 ) 2 (C 7 H 12 ) (3) tol-d 8 10 W(NAr)(OSiPh 3 ) 2 (C 8 H 14 ) (4) tol-d 8 11 W(NAr)(OSiPh3)2(C8H14) (4) thf-d8 7.0 W(NAr)(ORF3)2(C8H14) (5) tol-d8 3.0 W(NPh)(OR F3 ) 2 (C 8 H 14 ) (6) tol-d 8 3.0 W (NAr)(OSiPh 3 ) 2 (C 6 H 10 NPh) (8) tol-d 8 8.0 Upon photolysis in a ⁇ 93 mW LED photoreactor (445 n
  • W(NPh)(ORF3)2(C8H14) (6) upon photolysis is not much different from the other photolyses that yield the alkylidenes shown in eq 9, but W(NPh)(ORF3)2(CHC7H13) complexes are susceptible to bimolecular alkylidene coupling to give various olefin isomers (eq 11) at a rate competitive with formation of the alkylidene itself.
  • W(NAr)(ORF3)2(CHC7H13) ( Figure 22), is stable toward bimolecular decomposition under comparable concentrations ( ⁇ 0.01 mM), a fact that we ascribe to the larger size of the NAr ligand relative to the NPh ligand.
  • tungstacyclopentanes with substitution patterns different from those described here may be susceptible to thermal rearrangements to alkylidenes, but it seems unlikely that the electronic transition can be reduced in energy to a thermally accessible value in ⁇ ⁇ ⁇ '-disubstituted tungstacyclopentanes. It remains to be determined whether tungstacyclopentanes or tungstabicycloalkanes that do not fall into the category of SP ⁇ ⁇ ⁇ '-disubstituted metallacyclopentanes can be converted into alkylidenes thermally in the absence of light.
  • the bicyclic complexes can be prepared from the unsubstituted tungstacyclopentane complexes, or more conveniently from dialkoxide dichloride complexes using diethyl zinc as the reducing agent in the presence of 1,6-heptadiene or 1,7-octadiene.
  • An analog of a 7- tungstabicylo[3.3.0]octane complex can be prepared from diallylaniline, but not diallylether due to binding of the ether oxygen to the metal in a diallyether/ethylene intermediate ⁇ -substituted tungstacyclopentane complex.
  • Tetrahydrofuran, diethyl ether, dichloromethane, and toluene were dried and deoxygenated by argon purge followed by passage through activated alumina in a solvent purification system followed by storage over 4 ⁇ molecular sieves.
  • Non- halogenated and non-nitrile containing solvents were tested with a standard purple solution of sodium benzophenone ketyl in THF to confirm effective oxygen and moisture removal prior to use.
  • NaOSiPh 3 was made from Ph 3 SiOH and NaH in Et 2 O at room temperature.
  • EtMgBr was used as received from Sigma-Aldrich.
  • Ethylene Ultra High Purity was used as received from Airgas. Elemental analyses were performed at Atlantic Microlab, Inc., Norcross, GA.
  • Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc., degassed, and dried over activated 4 ⁇ molecular sieves for at least 24 h prior to use.
  • NMR spectra were recorded on Bruker Avance 600 MHz, Bruker Avance 500 MHz and Bruker Avance 300 MHz spectrometers.
  • 1 H and 13 C chemical shifts are reported in ppm relative to tetramethylsilane using residual solvent as an internal standard.
  • 19 F and 31 P chemical shifts are reported in ppm relative to respectively trichloro- fluoro-methane and H3PO4 as external standards.
  • W(NAr)(ORF3)2Cl2(THF)(600 mg, 0.79 mmol, 1 eq.) was dissolved in toluene (120 mL) in a 1L J. Young Flask. The solution was subject to three freeze-pump-thaw cycles, and then 15 psi of ethylene was added. The solution was then cooled to -78°C and Et 2 Zn (1M in hexane, 0.79 mL, 0.79 mmol, 1 eq.) was added dropwise. The solution was brought back to room temperature in the dark and stirred overnight (under ethylene). The solvents were removed from the reaction mixture in vacuo and the dark yellow residue was extracted in pentane (40 mL).
  • W(NAr)(OSiPh3)2(C8H14) (4).
  • W(NAr)(OSiPh3)2(C4H8) 100 mg, 0.104 mmol
  • 1,7-octadiene 34 mg, 0.32 mmol, 3 equiv.
  • toluene 10 mL
  • W(NAr)(ORF3)2(C8H14) (5) W(NAr)Cl 2 (OR F3 ) 2 (THF) (300 mg, 0.396 mmol, 1 equiv.), 1,7-octadiene (65 mg, 0.594 mmol, 1.5 equiv.) and toluene (60 mL) were added to a 500 mL J-Y flask. The reaction mixture was cooled to -78 °C and Et2Zn (1 equiv.) was added dropwise. The mixture was stirred overnight at room temperature and then heated in an oil bath at 80 °C and for 4 h. All volatiles were removed under vacuum and the solid residue was extracted with 10 mL of pentane.
  • W(NAr)(OSiPh3)2[ ⁇ -(CH2OCH2CH CH2)C4H7] (7) W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.104 mmol), diallyl ether (30.6 mg, 0.31 mmol, 3 equiv.), and toluene (6 mL) were added to a 100 mL J-Y flask, and the flask was heated for 20 h at room temperature. The volatiles were removed under vacuum and the solid residue was extracted into 10 mL of pentane. This solution was filtered through a plug of Celite, and the solvent was removed in vacuo to afford a yellow foam.
  • W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.1 mmol), N,N-diallylaniline (18 mg, 0.1 mmol, 1 equiv.) and toluene (10 mL) were added to a 100 mL J-Y flask, and the flask was heated at 80 °C for 6 h. The volatiles were removed under vacuum and the solid residue was extracted with 15 mL of pentane. This solution was filtered through a plug of Celite. The solvent was removed in vacuo to afford a yellow foam which was then dissolved in 2 mL of pentane and the solution was kept at -30°C. The desired compound oiled out from the pentane solution.
  • W(NAr)(CHC6H11NPh)(OSiPh3)2 (12) W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.1 mmol), N,N-diallylaniline (18 mg, 0.1 mmol, 1 equiv.) and toluene (10 mL) were added to a 100 mL J-Y flask, and the flask was heated at 80 °C for 6 h. The volatiles were removed under vacuum and the solid residue was extracted with 15 mL of pentane. This solution was filtered through a plug of Celite.
  • molybdacyclopentane complexes especially substituted ones, are that molybdacyclopentanes are likely to lose an olefin to form Mo(IV) olefin complexes more readily than tungstacyclopentanes, and secondly, that metathesis reactions could outcompete formation of molybdacyclopentanes and complicate their identification or isolation.
  • a third problem is that terminal olefins might be isomerized to internal olefins by Mo(NR)(OR')2(olefin) complexes, presumably via an allyl hydride intermediate.
  • the proton NMR spectrum of 4 is analogous to that for W(NAr)(OSiPh 3 ) 2 (trans- 5,6-C 8 H 14 ), except the ⁇ proton resonances in the bicycle are not resolved at 22 °C as they are in W(NAr)(OSiPh 3 ) 2 (trans-5,6-C 8 H 14 ).
  • the four ⁇ proton resonances in the spectrum of 4 appear between 2.5 and 3.3 ppm (see Figure 23); other resonances can be identified through proton/proton correlations.
  • the two ⁇ carbon resonances are found at v and w, and the two ⁇ carbon resonances at x and y ppm.
  • Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) has decomposed and cyclohexene
  • Mo(NAr)(OSiPh 3 ) 2 (C 2 H 4 ) are formed in what appears to be a metathesis ring-closing of 1,7-octadiene. But exactly how "free" 1,7-octadiene is formed, if that is the case, is not clear at this stage.
  • a SCXRD of a crystal grown from a pentane solution showed it to be approximately a 1:1 mixture of Mo(NAr)(OSiPh 3 ) 2 (trans-5,6-C 8 H 14 ) and Mo(NAr)(OSiPh 3 ) 2 (cis-5,6-C 8 H 14 ).
  • Other crystals obtained under other conditions are likely to have different ratios of the two compounds in a given crystal.
  • a SCXRD study of a crystal obtained from a pentane solution of the mixture of alkylidenes was found to be the syn isomer of the alkylidene derived from Mo(NAr)(OSiPh3)2(trans-5,6- C 8 H 14 ), i.e., syn-Mo(NAr)(OSiPh 3 ) 2 (trans-CHC 7 H 13 ).
  • the rate of consumption of Mo(NAr)(OSiPh3)2(5,6-C8H14) in C6D6 under 450 nm LED light was found to be ⁇ 25% of the rate of consumption of the analogous tungsten complex.

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Abstract

Certain embodiments of the invention provide metathesis catalyst compound(s) and composition. Certain embodiments of the invention provide a method of preparing or activating metathesis catalyst compound or composition.

Description

CATALYST COMPOSITIONS AND METHODS THEREOF CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to United States Provisional Application Number 63/525,864 that was filed on July 10, 2023. The entire content of the application referenced above is hereby incorporated by reference herein. BACKGROUND OF THE INVENTION Transition metal-catalyzed olefin metathesis has been shown to be useful in the synthesis of numerous valuable chemicals. Metal alkylidene complexes have been shown to perform olefin metathesis. However, in many cases, multi-step syntheses are required to generate the catalyst composition. On the other hand, metallacyclopentanes were considered as metathesis-inactive products of metathesis and may impact the catalytic performance and longevity. Thus, new methods for efficiently producing and/or regenerating metathesis catalyst compositions are needed. SUMMARY OF THE INVENTION Certain embodiments of the invention provide a method of converting a metathesis- inactive compound into a metathesis-active compound, comprising irradiating the metathesis- inactive compound with light. Certain embodiments of the invention provide a method for converting a tungsten or molybdenum based ^, ^'-dialkyl metallacyclopentane compound into its metal-alkylidene isomer, comprising irradiating the ^, ^’-dialkyl metallacyclopentane compound with light, wherein the ^, ^’-dialkyl groups taken together with the ^, ^’ carbons may optionally form a ring fused to the metallacyclopentane ring. Certain embodiments of the invention provide a method for converting a tungsten or molybdenum based unsubstituted metallacyclopentane compound into a ^, ^’-dialkyl metallacyclopentane compound. Certain embodiments of the invention provide a compound of Formula II or Formula III
Figure imgf000002_0001
wherein M is molybdenum (Mo) or tungsten (W); the two R groups are each independently alkyl, or the two R groups taken together with the intervening carbon atoms form a ring A, wherein one carbon atom of the ring A is optionally replaced with -(NRe)-; wherein the two R groups or the ring is each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; Z is O, or NRa; X and Y are each independently ORb, N(Rc)2, or heteroaryl; Ra is alkyl, adamantyl, or aryl; Rb is alkyl, aryl, or Si(Rd)3; Rc is alkyl, or aryl; Rd is aryl; Re is alkyl, or aryl; and wherein each aryl of Ra, Rb, Rc, Rd, Re and R, and each heteroaryl of R, X and Y is independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, and (C1-C6) alkyl optionally substituted with one or more halo; wherein each alkyl of Ra, Rb, Rc, and Re is independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, aryl, and heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino. Certain embodiments of the invention provide a compound of Formula II, or Formula III. Certain embodiments of the invention provide one or more compounds of Formula II and/or Formula III, or mixture thereof. Certain embodiments of the invention provide a method for producing a catalyst compound of formula III or activating a compound of formula II, comprising irradiating the compound of formula II with light. Certain embodiments of the invention provide a catalyst compound or composition (e.g., metathesis compound or catalyst composition). Certain embodiments of the invention provide a method of catalyzing a metathesis reaction, comprising contacting one or more reactant compound (e.g., alkene) with a compound described herein, or a catalyst composition comprising one or more compound described herein. Certain embodiments of the invention provide a reaction as described herein. Certain embodiments of the invention provide a catalytic cycle, or step thereof, as described herein. Certain embodiments of the invention provide a compound (e.g., a complex, an adduct, or an intermediate) as described herein. Certain embodiments of the invention provide a method of making or using a compound, or a catalyst composition as described herein. Certain embodiments of the invention provide the use of a compound, or a catalyst composition for a metathesis reaction. Certain embodiments provide a compound as described herein. Certain embodiments provide a mixture as described herein. Certain embodiments provide a composition as described herein. Certain embodiments provide a method as described herein. The invention also provides processes and intermediates disclosed herein that are useful for preparing a compound or composition described herein. BRIEF DESCRIPTION OF THE FIGURES Figure 1. Molecular structure of square pyramidal trans-W(β,β'-Me2C4H6). Ellipsoids are plotted at a 50% probability level. Hydrogen atoms, solvent molecules, and low occupancy disordered components are omitted for clarity. Figure 2. Eyring plot three rate constants at three temperatures for photolyses of W(β,β'- Me2C4H6). Figure 3. Absorption envelopes for W(C4H8) (top) and W(β,β'-Me2C4H6) (bottom) calculated by TD-DFT (see SI) with the first excited state at ~380 nm corresponding to the promotion of an electron from the W-C bonds (HOMO) into the dxy orbital (LUMO). Figure 4. Improved Synthesis of ^, ^’-Dimethyl-WC4(NCPh3)(OSiPh3)2. Figure 5. Photoinduced reactivity of ^, ^’-Dimethyl-WC4(NCPh3)(OSiPh3)2. Figure 6. Photoinduced reactivity of ^, ^’-Dimethyl-WC4(NCPh3)(OSiPh3)2. Figure 7. New Syntheses of Tungstacyclopentanes. Figure 8. Synthesis of Tungstabicycle from 1,6-Heptadiene. Figure 9. Synthesis of Tungstabicycle from 1,7-Octadiene. Figure 10. Photolysis of 1,7-Octadiene Bicycle. Figure 11. One pot Synthesis of bicycle/alkylidene from dichloride. Figure 12. Molecular structure of square pyramidal 7-tungstabicyclo[3.3.0.]octane- W(C7H12). Ellipsoids are plotted at a 50% probability level. Hydrogen atoms, solvent molecules, and low occupancy disordered components are omitted for clarity. Figure 13. Variable temperature proton NMR spectra of the tungstacyclopentane ring protons in W(NPh)(OsiPh3)2(C4H8) (1). Figure 14. Molecular structure of W(NPh)(OsiPh3)2(C4H8) (1) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 15. Molecular structure of W(NAr)(OsiPh3)2(C7H12) (3) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 16. Molecular structure of W(NAr)(OsiPh3)2(trans-C8H14) (4) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 17. Molecular structure of W(NAr)(ORF3)2(trans-C8H14) (5) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 18. Molecular structure of W(NPh)(ORF3)2(cis-C8H14) (6a) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 19. Formation of an equilibrium mixture of the cis (6a) and trans (6b) isomers of 6. Figure 20. Molecular structure of W(NPh)(ORF3)2(trans-C8H14) (6b) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 21. Molecular structure of W(NAr)(OSiPh3)2[ ^-(CH2OCH2CH=CH2)C4H7] (7) as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 22. The molecular structure of 10 as determined by SCXRD. Ellipsoids are plotted at 50% probability level. Hydrogen atoms are omitted for clarity. Figure 23. Partial proton NMR spectrum for Mo(NAr)(OSiPh3)2(trans-5,6-C8H14). Figure 24. SCXRD of a mixture of co-crystallized Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) and Mo(NAr)(OSiPh3)2(cis-5,6-C8H14). Figure 25. Alkylidenes obtained in solution through irradiation of Mo(NAr)(OSiPh3)2(5,6-C8H14). Figure 26. SCXRD of syn-Mo(NAr)(OSiPh3)2(trans-CHC7H13). Figure 27. Synthesis of compound having pyrrolide ligand. Figure 28. Synthesis of compound having pyrrolide ligand. Figure 29. Synthesis of compound having pyrrolide ligands. DETAILED DESCRIPTION New metathesis catalyst compounds and a facile method for producing such compounds are described herein. In particular, by photoactivation, a metal-alkylidene compound could be produced from a ^ ^ ^' disubstituted metallacyclopentane compound. Without wanting to bound by theory, photoactivation of the ^ ^ ^' disubstituted compound into the metal-alkylidene compound may be primarily mediated through ^ hydrogen migration within metallacyclopentane. Also described herein are methods to prepare the ^ ^ ^' disubstituted compound from an unsubstituted metallacyclopentane compound, which is obtainable from, e.g., metal dichloride precursors. In addition, also described herein is a method for catalyzing metathesis reaction by contacting one or more reactant compound with a metathesis compound or composition described herein. The metathesis catalyst composition may comprise a metathesis-active compound described herein and/or may comprise a metathesis-inactive compound that could be activated (e.g., via irradiation of light as described herein). Compounds Certain embodiments of the invention provide a tungsten or molybdenum based ^, ^'- dialkyl metallacyclopentane compound and its metal-alkylidene isomer. Metallacyclopentane ring is a 5-membered, MC4 ring. The two carbon atoms immediately adjacent to M are ^ and ^' carbons, and the two carbon atoms second next to M are ^, ^' carbon atoms. The tungsten or molybdenum based metallacyclopentane compound described herein are disubstituted on ^, ^' carbon atoms with two alkyl groups respectively. In certain embodiments, the ^, ^'-dialkyl groups taken together with the ^, ^' carbons may form a ring A that is fused to the metallacyclopentane ring, thus providing a bicyclic compound. The tungsten or molybdenum based ^, ^'-dialkyl metallacyclopentane compound may be converted to its metal-alkylidene isomer as described herein. Without wanting to be bound by theory, one ^ hydrogen may migrate within metallacyclopentane to the other ^ carbon, and/or one M-C ^ bond may sever while the other forms M=C ^ bond, converting the metallacyclopentane compound to the metal-alkylidene form. Certain embodiments of the invention provide a compound of Formula I, Formula II, or Formula III
Figure imgf000006_0001
wherein M is molybdenum (Mo) or tungsten (W); the two R groups are each independently alkyl (e.g., C1-C16 or C2-C8), or the two R groups taken together with the intervening carbon atoms form a ring A, wherein one carbon atom of the ring A is optionally replaced with -(NRe)-; wherein the two R groups or the ring is each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; Z is O, or NRa; X and Y are each independently ORb, N(Rc)2, or heteroaryl; Ra is alkyl, adamantyl, or aryl; Rb is alkyl, aryl, or Si(Rd)3; Rc is alkyl, or aryl; Rd is aryl; Re is alkyl, or aryl; and wherein each aryl of Ra, Rb, Rc, Rd, Re, and R, and each heteroaryl of R, X and Y is independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, and (C1-C6) alkyl optionally substituted with one or more halo; wherein each alkyl of Ra, Rb, Rc, and Re is independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, aryl, and heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino. Formula I, Formula II, or Formula III above are drawn in a manner that includes all of square pyramidal (SP), trigonal bipyramidal (TBP), syn, anti, cis, trans, or stereochemical isomers and possibilities. In certain embodiments, the compound is a compound of Formula II, or Formula III. In certain embodiments, the compound is a metathesis-active compound that could catalyze a metathesis reaction. In certain embodiments, the compound is a metal-alkylidene compound. In certain embodiments, the compound is a compound of Formula III. In certain embodiments, the compound is a ^ ^ ^' disubstituted metallacyclopentane compound. In certain embodiments, the compound is a compound of Formula II. In certain embodiments, the compound is an unsubstituted metallacyclopentane compound. In certain embodiments, the compound is a compound of Formula I. In certain embodiments, illustrative examples of the two R groups and/or other groups (X, Y, Z, or M) in the compound of Formula I, Formula II, or Formula III are as follows. In certain embodiments, M is tungsten (W). In certain embodiments, M is molybdenum (Mo). In certain embodiments, the compound of Formula I or Formula II may adopt a square pyramidal (SP) configuration. In certain embodiments, the metallacyclopentane ring is disubstituted on ^ and ^' carbons. In certain embodiments, the compound of Formual II is a trans- ^ ^ ^' disubstituted metallacyclopentane compound, wherein the two R groups are in trans- configuration. In certain embodiments, the compound of Formual III is a trans- ^ ^ ^' disubstituted metal-alkylidene compound. In certain embodiments, the compound of Formual II is a cis- ^ ^ ^' disubstituted metallacyclopentane compound, wherein the two R groups are in cis- configuration. In certain embodiments, the compound of Formual III is a cis- ^ ^ ^' disubstituted metal-alkylidene compound. The ^ ^ ^' carbons of the metal-alkylidene compound are carbon atoms that are second or third next to the metal atom. In certain embodiments, the compound has structure of Formula IIa’:
Figure imgf000008_0001
. In certain embodiments, the compound has structure of Formula IIa’’:
Figure imgf000008_0002
. In certain embodiments, the compound has structure of Formula IIIanti
Figure imgf000008_0003
. In certain embodiments, the compound has structure of Formula IIIsyn . In certain embodiments, the compound has structure of Formula IIIa
Figure imgf000009_0001
. Formula IIIa above is drawn in a manner that is a syn metal-alkylidene compound. In certain embodiments, the two R groups are each independently (C1-C16), (C2-C16), (C3-C16), or (C4-C16) alkyl. In certain embodiments, the two R groups are each independently (C1-C12), (C2-C12), (C3-C12), or (C4-C12) alkyl. In certain embodiments, the two R groups are each independently (C1-C10), (C2-C10), (C3-C10), or (C4-C10) alkyl. In certain embodiments, the two R groups are each independently (C1-C8), (C2-C8), (C3- C8), or (C4-C8) alkyl. In certain embodiments, the two R groups are each independently (C1-C6), (C2-C6), (C3- C6), or (C4-C6) alkyl. In certain embodiments, the two R groups are both methyl. In certain embodiments, the two R groups are not simultaneously methyl. In certain embodiments, the two R groups are each independently or both ethyl, propyl, butyl, pentyl, hexyl, heptanyl, or octanyl. In certain embodiments, the two R groups are each independently or both ethyl, 1- propyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptanyl, or 1-octanyl. In certain embodiments, the two R groups are both ethyl. In certain embodiments, the two R groups are each independently or both propyl (e.g., 1- propyl or isopropyl). In certain embodiments, the two R groups are each independently or both butyl (e.g., 1- butyl or 2-butyl). In certain embodiments, the two R groups are each independently or both pentyl (e.g., 1- pentyl or neopentyl). In certain embodiments, the two R groups are each independently or both hexyl (e.g., 1- hexyl, or 2-hexyl). In certain embodiments, the two R groups are each independently or both heptanyl (e.g., 1-heptanyl, or 2-heptanyl). In certain embodiments, the two R groups are each independently or both octanyl (e.g., 1-octanyl, or 2-octanyl). In certain embodiments, the two R groups are each independently unbranched alkyl. In certain embodiments, the two R groups are each independently branched alkyl. In certain embodiments, the two R groups as described herein are each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl. In certain embodiments, the two R groups are each independently, optionally substituted with one or more aryl (e.g., phenyl). In certain embodiments, the two R groups are each independently, optionally substituted with one or more heteroaryl. In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkoxy (e.g., C1-C6 alkoxy). In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkanoyl (e.g., C1-C6 alkanoyl). In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkoxycarbonyl (e.g., C1-C6 alkoxycarbonyl). In certain embodiments, the two R groups are each independently, optionally substituted with one or more alkanoyloxy (e.g., C1-C6 alkanoyloxy). In certain embodiments, the two R groups, taken together with the intervening carbon atoms (i.e., ^ ^ ^' carbons), form a ring. Accordingly, in a compound of Formula II, the ring is fused to the metallacyclopentane to form a bicyclic compound. In certain embodiments, the compound has structure of Formula IIb or Formula IIIb
Figure imgf000010_0001
wherein the two R groups taken together with the intervening carbon atoms form a ring A that is optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl. In certain embodiments, the compound has a structure of Formula IIbcis, wherein alpha and alpha’ carbon atoms of ring A are in cis configuration. In certain embodiments, the compound has a structure of Formula IIbtrans, wherein alpha and alpha’ carbon atoms of ring A are in trans configuration. As used herein, the first carbon atom in ring A that is immediately next to the fused metallacyclopentane ring is alpha or alpha’ carbon atom of ring A, the second carbon atom in ring A is beta or beta’ carbon atom of ring A, the third carbon atom of ring A is gamma or gamma’ carbon atom of ring A. In certain embodiments, the ring A is a 3, 4, 5, 6, 7, 8, 9, or 10-membered ring. In certain embodiments, the ring A is a 5, or 6-membered ring. In certain embodiments, the ring A is not a 5, or 6-membered ring. In certain embodiments, the ring A is a 3, or 4-membered ring. In certain embodiments, the ring A is a 7, 8, 9, or 10-membered ring. In certain embodiments, the ring A is a 7, or 8-membered ring. In certain embodiments, the ring A is a (C3-C10) cycloalkane ring. In certain embodiments, the ring A is a (C3-C4) cycloalkane ring. In certain embodiments, the ring A is a (C5-C6) cycloalkane ring. In certain embodiments, the ring A is not a (C5-C6) cycloalkane ring. In certain embodiments, the ring A is a (C7-C10) cycloalkane ring. In certain embodiments, the ring A is a (C8-C10) cycloalkane ring. In certain embodiments, the ring A is a (C8-C9) cycloalkane ring. In certain embodiments, the ring A is a cyclopropane or cyclobutane ring. In certain embodiments, the ring A is a cyclopentane ring. In certain embodiments, the ring A is not a cyclopentane ring. In certain embodiments, the ring A is a cyclohexane ring. In certain embodiments, the ring A is not a cyclohexane ring. In certain embodiments, the ring A is a cycloheptane ring. In certain embodiments, the ring A is a cyclooctane ring. In certain embodiments, the ring A is a cyclononane ring. In certain embodiments, the ring A is a cyclodecane ring. In certain embodiments, the ring A is substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl. In certain embodiments, one carbon atom of ring A is replaced with -(NRe)-. In certain embodiments, a non-alpha carbon atom (e.g., beta carbon atom or gamma carbon atom) of ring A is replaced with -(NRe)-. In certain embodiments, beta carbon atom of ring A is replaced with -(NRe)-. In certain embodiments, the compound has structure of Formula IIb7
Figure imgf000012_0001
wherein Xa is -CH2- or -NRe-. In certain embodiments, the compound has structure of Formula IIb5
Figure imgf000012_0002
. In certain embodiments, the compound is not a compound having structure of Formula IIb5. In certain embodiments, the compound has structure of Formula IIb5′.
Figure imgf000012_0003
. In certain embodiments, the compound is not a compound having structure of Formula IIb5′. In certain embodiments, the compound has structure of Formula IIIb′ . Formula IIIb’ above is drawn in a manner that is a syn- metal-alkylidene compound. In certain embodiments, the ring A is cyclopentane. In certain embodiments, the ring A is not cyclopentane. In certain embodiments, the ring A is cyclohexane. In certain embodiments, the ring A is not cyclohexane. In certain embodiments, the compound is not a compound having structure of Formula IIIb′. In certain embodiments, wherein the compound has structure of Formula IIb6 or Formula IIb6′.
Figure imgf000013_0001
. In certain embodiments, the compound is not a compound having structure of Formula IIb6 or Formula IIb6′. Formula IIb, Formula IIb5, Formula IIb6, or Formula IIIb above are drawn in a manner that includes all of square pyramidal (SP), trigonal bipyramidal (TBP), syn, anti, cis, trans, or stereochemical isomers and possibilities. In certain embodiments, the compound has structure of Formula IIIbanti or Formula IIIbsyn
Figure imgf000013_0002
. In certain embodiments, the ring A is cyclopentane. In certain embodiments, the ring A is not cyclopentane. In certain embodiments, the ring A is cyclohexane. In certain embodiments, the ring A is not cyclohexane. In certain embodiments, Z is O. In certain embodiments, Z is NRa. In certain embodiments, Ra is aryl that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl (e.g., C1-C4 alkyl). In certain embodiments, Ra is phenyl that is optionally substituted with one or more (C1-C6) alkyl (e.g., isopropyl). In certain embodiments, Ra is phenyl. In certain embodiments, Ra is 2,6-diisopropylphenyl (2,6-i-Pr2C6H3). In certain embodiments, Ra is pentafluorophenyl (-C6F5). In certain embodiments, Ra is 2,6-dichlorophenyl. In certain embodiments, Ra is 2-Trifluoromethylphenyl. In certain embodiments, Ra is alkyl (e.g., C1-C6 alkyl) that is optionally substituted with one or more halo, hydroxy, amino, aryl, or heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino. In certain embodiments, Ra is tBu. In certain embodiments, Ra is methyl. In certain embodiments, Ra is a methyl group substituted with one or more aryl, for example, Ra is triphenylmethyl (-C(Ph)3). In certain embodiments, Ra is adamantyl. In certain embodiments, X and Y are each independently N(Rc)2. In certain embodiments, X and Y are each independently optionally substituted heteroaryl (e.g., 1-pyrrolyl, or 2,5-dimethyl-1-pyrrolyl). In certain embodiments, X and Y are each independently ORb, or N(Rc)2. In certain embodiments, X and Y are each independently ORb, or an optionally substituted heteroaryl (e.g., 1-pyrrolyl, or 2,5-dimethyl-1-pyrrolyl). In certain embodiments, X and Y are each independently ORb. In certain embodiments, Rb is alkyl (e.g., C1-C6 alkyl such as t-butyl) substituted with one or more halo (e.g., F). In certain embodiments, Rb is C(CF3)(CH3)2. In certain embodiments, Rb is Si(Rd)3, wherein Rd is aryl (e.g., phenyl) that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl (e.g., C1-C4 alkyl). In certain embodiments, X and Y are each OSi(Ph)3. In certain embodiments, X and Y are OSi(Ph)3 and optionally substituted heteroaryl (e.g., 2,5-dimethyl-1-pyrrolyl). In certain embodiments, X and Y are each optionally substituted heteroaryl. In certain embodiments, X and Y are each pyrrole-based ligand (e.g., 2,5-dimethylpyrrole ligand). In certain embodiments, X and Y are each 2,5-dimethyl-1-pyrrolyl. In certain embodiments, X and Y are each OC(CF3)(CH3)2. In certain embodiments, X and Y are optionally substituted heteroaryl (e.g., 2,5- dimethyl-1-pyrrolyl) and OC(CF3)(CH3)2. In certain embodiments, Rb is aryl that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl (e.g., C1-C4 alkyl). In certain embodiments, Rb is phenyl that is optionally substituted with one or more (C1-C6) alkyl (e.g., C1-C4 alkyl). In certain embodiments, Rb is phenyl. In certain embodiments, Rb is alkyl (e.g., C1-C8 alkyl) that is optionally substituted with one or more halo, hydroxy, amino, aryl, or heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino. In certain embodiments, Rb is tBu. In certain embodiments, Rb is C(CF3)(CH3)2, C(CF3)2CH3, or C(CF3)3. In certain embodiments, Rc is aryl that is optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl. In certain embodiments, Rc is phenyl that is optionally substituted with one or more alkyl (e.g., C1-C4 alkyl). In certain embodiments, Rc is phenyl. In certain embodiments, Rc is alkyl (e.g., C1-C8 alkyl) that is optionally substituted with one or more halo, hydroxy, amino, aryl, or heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino. Certain illustrative, non-limiting examples of compounds of Formula II or Formula III are as follows. In certain embodiments, the compound having structure of Formula I, Formula II or Formula III is a compound shown in Example 1. In certain embodiments, the compound having structure of Formula II is W(NCPh3)(OSiPh3)2(β,β'-Me2C4H6), or W(NCPh3)(OSiPh3)2(β,β'-Pent2C4H6). In certain embodiments, the compound having structure of Formula III is W(NCPh3)(OSiPh3)2(CHCH(Me)CHMe2), or W(NCPh3)(OSiPh3)2(CHCH(Pent)CH(Pent)CH3). In certain embodiments, the compound having structure of Formula II is
Figure imgf000015_0001
. In certain embodiments, the compound having structure of Formula III is
Figure imgf000015_0002
(including both syn and anti). In certain embodiments, the compound having structure of Formula II is not . In certain embodiments, the compound having structure of Formula III is not
Figure imgf000016_0001
(including both syn and anti). In certain embodiments, the compound having structure of Formula III is
Figure imgf000016_0002
. In certain embodiments, the compound having structure of Formula III is not
Figure imgf000016_0003
. In certain embodiments, the compound having structure of Formula II is
Figure imgf000016_0004
In certain embodiments, the compound having structure of Formula III is
Figure imgf000016_0005
(including both syn and anti). In certain embodiments, the compound having structure of Formula II is
Figure imgf000016_0006
In certain embodiments, the compound having structure of Formula III is (including both syn and anti), or . In certain embodiments, the compound having structure of Formula II is
Figure imgf000017_0001
, wherein Ar is 2,6-i-Pr2C6H3. In certain embodiments, the compound having structure of Formula II is , wherein Ar is 2,6-i-Pr2C6H3. In certain embodiments, the compound is Mo(NAr)(OSiPh3)2(trans-5,6-C8H14),
Figure imgf000017_0002
, wherein Ar is 2,6-i-Pr2C6H3. In certain embodiments, the compound having structure of Formula III is
Figure imgf000017_0003
, (including both syn and anti) wherein Ar is 2,6-i-Pr2C6H3. In certain embodiments, the compound having structure of Formula III is
Figure imgf000017_0004
, (including both syn and anti) wherein Ar is 2,6-i-Pr2C6H3. In certain embodiments, the compound is Mo(Nar)(OSiPh3)2(trans-CHC7H3),
Figure imgf000018_0001
(including both syn and anti) wherein Ar is 2,6-i-Pr2C6H3. In certain embodiments, the compound is syn-Mo(NAr)(OSiPh3)2(trans-CHC7H3). In certain embodiments, the compound having structure of Formula II is ,
Figure imgf000018_0002
wherein Ra is CPh3, or optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, Ra is 2,6-i-Pr2C6H3. In certain embodiments, the compound having structure of Formula III is
Figure imgf000018_0003
, (including both syn and anti) wherein RF3 is C(CF3)(CH3)2. In certain embodiments, the compound having structure of Formula II is wherein Ra is CPh3, or optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, Ra is 2,6-i-Pr2C6H3. In certain embodiments, the compound having structure of Formula III is
Figure imgf000019_0001
(structures including both syn and anti) wherein Ra is CPh3, or optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound having structure of Formula II or Formula III is a compound shown in Figures 4-11, wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound has structure of Formula II or Formula III, provided the compound is not a compound shown in Figures 4-11, wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound having structure of Formula II or Formula III is a compound of
Figure imgf000020_0001
, , wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound has structure of Formula II or Formula III, provided the compound is not a compound of
Figure imgf000021_0001
wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound having structure of Formula III is not (including both syn and anti), or . Certain embodiments of the invention provide a compound (e.g., a complex, an adduct, or an intermediate) described herein (also as described in Example 1). Certain embodiments of the invention provide one or more compound (e.g., a catalyst compound), or mixture thereof, as described herein. Certain embodiments of the invention provide one or more metathesis-active compound (e.g., a metathesis catalyst compound), or mixture thereof, as described herein. Certain compound (e.g., a catalyst compound) described herein could be generated using the exemplary synthetic schemes described herein (also see Example 1 or Figures 4-11). Catalyst Compositions Certain embodiments of the invention provide a catalyst composition comprising one or more compound(s) described herein (e.g., a compound of Formula III or Formula II). In certain embodiments, the catalyst composition is a metathesis catalyst composition. In certain embodiments, the catalyst composition could be activated with irradiation of light (e.g., blue light), for example, prior to catalyzing a metathesis reaction. In certain embodiments, the catalyst composition could be activated or reactivated with irradiation of light prior to, during, and/or after a metathesis reaction. The catalyst composition described herein encompasses initial catalyst composition (e.g., before the metathesis reaction begins) and also encompasses catalyst composition comprising a mixture of compounds formed during catalytic cycle(s) or in a reaction or method described herein. The metathesis reaction may lead to the formation of metathesis-inactive compound, which may be reactivated, or converted to a metathesis-active compound by a method described herein. In certain embodiments, the catalyst composition comprises a compound of Formula III as described herein. In certain embodiments, the catalyst composition comprises a compound of Formula III as described herein and does not comprise a compound of Formula II as described herein. In certain embodiments, the catalyst composition comprises a compound of Formula II as described herein. In certain embodiments, the catalyst composition comprises a compound of Formula III as described herein and a compound of Formula II as described herein. In certain embodiments, the catalyst composition comprises a metathesis-active compound and a metathesis-inactive compound, wherein the metathesis-active compound is derived from the metathesis-inactive compound (e.g., via irradiation of light as described herein). In certain embodiments, the catalyst composition comprises a compound of Formula III and a compound of Formula II,
Figure imgf000023_0001
wherein the compound of Formula III is derived from the compound of Formula II (e.g., via irradiation of light as described herein); and the two R groups are each independently, optionally substituted alkyl as described herein; or the two R groups taken together with the intervening carbon atoms form a ring that is optionally substituted as described herein. For example, in certain embodiments, the catalyst composition comprises a compound of Formula IIIb and a compound of Formula IIb,
Figure imgf000023_0002
wherein the compound of Formula IIIb is derived from the compound of Formula IIb (e.g., via irradiation of light as described herein). In certain embodiments, the catalyst composition comprises a compound of Formula IIIa and a compound of Formula IIa’’, wherein the compound of Formula IIIa is derived from the compound of Formula IIa’’ (e.g., via irradiation of light as described herein). In certain embodiments, the catalyst composition comprises two or more compounds described herein. In certain embodiments, the catalyst composition comprises three or more compounds described herein. In certain embodiments, the catalyst composition comprises four or more compounds described herein. In certain embodiments, the catalyst composition comprises a compound having structure of Formula IIIsyn and a compound having structure of Formula IIIanti
Figure imgf000024_0001
. In certain embodiments, the catalyst composition comprises a compound having structure of Formula IIIsyn and a compound having structure of Formula IIIanti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. For example, in certain embodiments, the catalyst composition comprises a compound having structure of Formula IIIbsyn and a compound having structure of Formula IIIbanti
Figure imgf000024_0002
. In certain embodiments, the catalyst composition comprises a compound having structure of Formula IIIbsyn and a compound having structure of Formula IIIbanti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. In certain embodiments, a catalyst composition described herein may comprise or further comprises a metal-alkylidene compound of formula V
Figure imgf000025_0001
, wherein Z, M, X, Y, and the R group are as described above in Formula I, Formula II, or Formula III. In certain embodiments, the compound of formula V is a metal-isopropylidene compound or wherein R is methyl. In certain embodiments, the metal-isopropylidene compound is W(NCPh3)(OSiPh3)2(CMe2). Without wanting to be bound by theory, while the compound of Formula III may be derived from the compound Formula II through metallacyclopentane alpha hydrogen migration process, the compound of formula V may be derived from the compound of Formula II through a metallacyclopentane ring contraction process. In certain embodiments, a catalyst composition described herein may comprise a compound of Formula III and a compound of Formula V. In certain embodiments, a catalyst composition described herein may comprise a compound of Formula III and a compound of Formula V at a ratio of about 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1. In certain embodiments, a catalyst composition described herein may comprise a compound of Formula III and a compound of Formula V at a ratio of about 4:1. In certain embodiments, a catalyst composition described herein may a compound of Formula III and a compound of Formula V at a ratio of about 10:1 to 2:1, or 8:1 to 3:1. Methods Certain embodiments of the invention provide a method for converting a tungsten or molybdenum based ^, ^'-dialkyl metallacyclopentane compound into its metal-alkylidene isomer, comprising irradiating the ^, ^’-dialkyl metallacyclopentane compound with light, wherein the ^, ^’-dialkyl groups taken together with the ^, ^’ carbons may optionally form a ring A fused to the metallacyclopentane ring. Certain embodiments of the invention provide a method for producing a catalyst compound of formula III, comprising irradiating a compound of formula II with light. Certain embodiments of the invention provide a method for activating or converting a compound of formula II into a compound of formula III, comprising irradiating the compound of formula II with light. In certain embodiments, the light comprises or consists of visible light. In certain embodiments, the light comprises or consists of blue light. In certain embodiments, the light comprises or consists of UV light. In certain embodiments, the light comprises or consists of a wavelength range of about 260 to 750nm, or 380 to 750nm. In certain embodiments, the light comprises or consists of a wavelength range of about 385-720nm, 390-600nm, 395-530nm, 400-525nm, 405-520nm, 405- 515nm, 405-510nm, 405 to 500nm, 410 to 490nm, or 420 to 480nm. In certain embodiments, the light is blue light comprising or consisting of a wavelength range of about 380-500nm, 390-470nm, or 400-450nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 520, 510, 500, 490, 480, 470, 460, 450, 446, 445, 440, 430, 420, 410, 405, or 400nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 446, 445, or 405nm. In certain embodiments, the blue light comprises or consists of a wavelength of 405, 410, 420, 430, 440, 450, or 460nm. In certain embodiments, the blue light comprises or consists of a wavelength that is less than about 520, 510, 500, 490, 480, 470, 460, 450, 445, 440, 430, 420, 410, 409, 408, 407, or 406nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 450, 445, 446, or 405nm. In certain embodiments, light irradiation is provided by a light source emitting a light spectrum that comprises or consists of a wavelength range described herein (e.g., about 380 to 750nm). In certain embodiments, light irradiation is provided using a narrow band light source such as LED or laser. In certain embodiments, light irradiation is provided by a blue LED light source (e.g., 405nm, or 460nm). In certain embodiments, light irradiation is provided by a blue laser. In certain embodiments, light irradiation is provided by a light source as described herein (e.g., 405 ^max or 445-446 nm ^max LED light in Examples). As used herein, “blue light” refers to a light that comprises or consists of a wavelength range of 380-520nm or a portion thereof (e.g., 400-500nm, 445-450nm, 405-446nm, 405- 445nm, 445-446nm, or 404-406nm). The light source may be a light bulb, tube, strip, or array of light sources. In certain embodiments, the light source does not emit green, yellow, and/or red light. For example, in certain embodiments, the light source does not emit light with the wavelength range of about 530 to 750nm, 550 to 730nm, or 600 to 700nm. In certain embodiments, light irradiation is provided using a broad band light source, e.g., that may emit a continuous spectrum of light, such as extending from UV to near infrared such as about 300-1400 nm. In certain embodiments, the light is ambient light. In certain embodiments, light irradiation is provided using an incandescent or fluorescent light source. In certain embodiments, the light is sunlight. In certain embodiments, the light comprises UV light comprising a wavelength range of about 280 to 380nm, 280 to 360nm, 280 to 315nm, 290 to 305nm, 290 to 300nm, 280 to 310nm, 315 to 360nm, or 315 to 380nm. In certain embodiments, the light is UV light comprising or consisting of a wavelength range of about 280 to 380nm, 280 to 360nm, 280 to 315nm, 290 to 305nm, 280 to 310nm, 315 to 360nm, or 315 to 380nm. In certain embodiments, the UV light comprises or consists of a wavelength of about 312nm. In certain embodiments, light irradiation is provided by a UV light source (e.g., UV lamp). The light source brightness and/or wattage may vary to suit the requirements of reactions at different scales. For example, in certain embodiments, the light source may have a wattage of about 1, 10, 50, 100, 200, 400, 600, or 800mW. In certain embodiments, the light source may have a wattage of about 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000W, or higher. In certain embodiments, the light source may have a wattage of about 1mW to 2000W, 60mW to 600W, or 100mW to 400W. In certain embodiments, the light source may have a brightness of about 1 to 100,000, 10 to 10,000, 100 to 3000, or 1000 to 5000 lumens. In certain embodiments, the compound of formula II is irradiated with light without heating (e.g., at room temperature such as at about 20-25 °C). In certain embodiments, the compound of formula II is irradiated with light with cooling at a temperature that is lower than room temperature. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is lower than 20, 15, 10, 5, 0, -5, -10, -20, -30, -40, -50, -60, -70, -80, -90, or -100°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is lower than -40, -50, -60, -70, -80, -90, or -100°C. In certain embodiments, the compound of formula II is irradiated with light at about 5- 20°C. In certain embodiments, the compound of formula II is irradiated with light at about 0- 4°C. In certain embodiments, the compound of formula II is irradiated with light at about 0 to - 90°C, -10 to -85°C, -20 to -80°C. In certain embodiments, the compound of formula II is irradiated with light at about -10, -20, -30, -40, -50, -60, -70, -80, or -90°C. In certain embodiments, the compound of formula II is irradiated with light at about -30 or -80°C. In certain embodiments, the compound of formula II is irradiated with light at about -40 to -90°C, -45 to -85°C, -50 to -80°C. In certain embodiments, the compound of formula II is irradiated with light with heating (e.g., to a temperature that is above room temperature). In certain embodiments, the compound of formula II is irradiated with light at about 30-50°C, or 35-45°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is about 30, 35, 40, 45, or 50°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is at least about 30, 35, 40, 45, or 50°C. Although in certain situation, light irradiation (in particular, at high power) or close proximity with a light source may convey heat, heating as used herein only refers to temperature control provided by a temperature control apparatus or a heating source other than the light source. In certain embodiments, the compound of formula II is irradiated with light for about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23hrs, 1 day, 2 days, or longer. In certain embodiments, the compound of formula II is irradiated with light for about 0.5-16hrs, 1-12hrs, 1-9hrs, 1.5-8hrs, 2-6hrs, or 2-4hrs. In certain embodiments, the compound of formula II is irradiated with light for about 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 hrs. In certain embodiments, the methods described herein may produce a compound having structure of Formula IIIsyn and a compound having structure of Formula IIIanti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. In certain embodiments, the methods described herein may produce a compound having structure of Formula IIIbsyn and a compound having structure of Formula IIIbanti at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. In certain embodiments, the produced compound of formula III is a compound described herein (e.g., as described above, or in Example 1, or in Figures). In certain embodiments, the produced compound of formula III the compound is not a compound of
Figure imgf000028_0001
wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the compound of Formula III is produced in a reaction condition that is free of acid or in the absence of proton (e.g., in a solution free of acid or proton). In certain embodiments, the method for producing compound of Formula III (or activating compound of Formula II) may further produce a metallacyclopentane ring contraction product, or a metal-alkylidene compound of formula V
Figure imgf000029_0001
, wherein Z, M, X, Y, and the R group are as described above in Formula I, Formula II, or Formula III. In certain embodiments, the compound of formula V is a metal-isopropylidene compound or wherein R is methyl. In certain embodiments, the metal-alkylidene compound is W(NCPh3)(OSiPh3)2(CMe2). Without wanting to be bound by theory, while the compound of Formula III may be derived from the compound Formula II through metallacyclopentane alpha hydrogen migration process, the compound of formula V may be derived from the compound of Formula II through a metallacyclopentane ring contraction process. In certain embodiments, a compound of Formula III and a compound of Formula V are produced at a ratio of about 10:1, 9:1, 8:1, 6:1, 5:1, 4:1, 3:1, or 2:1. In certain embodiments, a compound of Formula III and a compound of Formula V are produced at a ratio of about 4:1. In certain embodiments, a compound of Formula III and a compound of Formula V are produced at a ratio of about 10:1 to 2:1, or 8:1 to 3:1. In certain embodiments, a compound of Formula V may be produced when irradiation of light on compound of Formula II is conducted without cooling. In certain embodiments, a compound of Formula V may be produced when irradiation of light on compound of Formula II is conducted with heating. In certain embodiments, a compound of Formula V is produced when irradiation of light on compound of Formula II is conducted at a temperature of about 15-35°C, 20-30°C, or 22-25°C. In certain embodiments, a compound of Formula V is produced when irradiation of light on compound of Formula II is conducted at about room temperature. In addition, in certain embodiments, the method for producing a catalyst compound of formula III (or activating a compound of formula II) further comprises producing compound of formula II by contacting a compound of Formula I with an alkene compound. In certain embodiments, the alkene compound is a terminal alkene compound comprising one or two terminal C=C bond. Accordingly, certain embodiments of the invention provide a method of producing compound of formula II by contacting a compound of Formula I with an alkene compound. In certain embodiments, the alkene compound is a terminal alkene compound comprising one or two terminal C=C bond. In certain embodiments, the alkene compound is C3-C18, C4-C18, or C5-C18 alkene. In certain embodiments, the alkene compound is C3-C16, C4-C16, or C5-C16 alkene. In certain embodiments, the alkene compound is C3-C14, C4-C14, or C5-C14 alkene. In certain embodiments, the alkene compound is C3-C12, C4-C12, or C5-C12 alkene. In certain embodiments, the alkene compound is C3-C10, C4-C10, or C5-C10 alkene. In certain embodiments, the alkene compound is C3-C8, C4-C8, or C5-C8 alkene. In certain embodiments, the alkene compound is C3-C7, C4-C7, or C5-C7 alkene. In certain embodiments, the alkene compound is C3-C6, C4-C6, or C5-C6 alkene. In certain embodiments, the alkene compound is propene. In certain embodiments, the alkene compound is not propene. In certain embodiments, the alkene compound is 1-butene. In certain embodiments, the alkene compound is 1-pentene. In certain embodiments, the alkene compound is 1-hexene. In certain embodiments, the alkene compound is 1-heptene. In certain embodiments, the alkene compound is 1-octene. In certain embodiments, the alkene compound is 1-nonene. In certain embodiments, the alkene compound is 1-decene. In certain embodiments, the alkene compound is 1,4-pentadiene. In certain embodiments, the alkene compound is 1,5-hexadiene. In certain embodiments, the alkene compound is 1,6-heptadiene. In certain embodiments, the alkene compound is not 1,6-heptadiene. In certain embodiments, the alkene compound is 1,7-octadiene. In certain embodiments, the alkene compound is not 1,7-octadiene. In certain embodiments, the alkene compound is 1,8-nonadiene. In certain embodiments, the alkene compound is 1,9-decadiene. In certain embodiments, the alkene compound is substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; wherein the aryl or heteroaryl is independently, optionally substituted with one or more halo, hydroxy, amino, or (C1-C6) alkyl. In certain embodiments, the alkene compound is N,N-Diallylaniline. In certain embodiments, the alkene compound is Diallylamine. In certain embodiments, the alkene compound is Diallyl-methyl-amine or Diallyl-ethyl-amine. In certain embodiments, the alkene compound is N,N-Di(3-butenyl)aniline. In certain embodiments, the alkene compound is dissolved in organic solution for contacting a compound of Formula I. In certain embodiments, a gaseous alkene compound is supplied (e.g., under about 1 atmospheric pressure) for contacting a compound of Formula I. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted in the dark. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of about 70-110°C, 73-100°C, 75-95°C, 78-90°C, or 80-88°C. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of about 90-110°C, 90-105°C, 90-95°C, or 95-100°C. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of about, or at least about, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90°C. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted with heating at a temperature of at least about, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100°C. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted without heating (e.g., at about room temperature of about 20-25°C). In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted for about 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23hrs, 1 day, 2 days, or longer. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) is conducted for about 1-24hrs, 1-16hrs, 1-12hrs, 1-8hrs, 2-6hrs, or 2- 3hrs. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) further comprises removing volatile material (e.g., ethylene and/or organic solvent such as toluene). In certain embodiments, removing volatile material comprises applying vacuum. Accordingly, in certain embodiments, the producing compound of formula II comprises step a), and one or more step of b), c), d) and e): a) contacting a compound of formula I with an alkene compound, b) preventing light exposure (prior to, or during the contacting), c) heating to a temperature as described herein (e.g., 70-100°C), d) removing volatile material, and e) dissolving residue in organic solvent (e.g., toluene). In certain embodiments, the producing compound of formula II comprising steps a), b), c), d), and/or e) is one round of reaction, which could be repeated for two or more times. In each round of reaction alkene compound is supplied and after a period of reaction (e.g., 2-3hrs or as described herein) volatile material is removed, overall, to improve yield, purity or drive complete conversion of a compound of formula I to the beta, beta’-disubstituted compound of Formula II. As one non-limiting example, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) could be conducted in the dark with heating at about 80-85°C for about 2-6hrs or 2-12hrs, followed by applying vacuum to remove volatile material and redissolving residues in organic solvent. This process could be repeated for two or three times or more. In certain embodiments, the produced compound of formula II the compound is a compound described herein (e.g., as described above, or in Example 1, or in Figures). In certain embodiments, the methods described herein may produce a mixture comprising a compound of Formula IIbcis and a compound of Formula IIbtrans at a ratio of about 30:1, 20:1, 15:1, 10:1, 9:1, 8:1, 7:3, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. In certain embodiments, the methods described herein may produce a mixture comprising a compound of Formula IIbcis and a compound of Formula IIbtrans at a ratio of about 7:3. In certain embodiments, the producing compound of formula II (by contacting a compound of Formula I with an alkene compound) further comprises heating a mixture (e.g., at 45-55°C, such as 50 °C) for 2-48hrs (e.g., 12-36hrs, or 24hrs) to generate an equilibrium mixture. In certain embodiments, an equilibrium mixture comprises a compound of Formula IIbcis and a compound of Formula IIbtrans at a ratio of about1:6, 1:7, 1:8, or 3:22. In certain embodiments, the produced compound of formula II the compound is not a compound of
Figure imgf000033_0001
wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3). In certain embodiments, the method for producing a compound of formula III and/or formula II further comprises firstly producing compound of formula I by contacting a metal- dichloride compound of formula IV with ethylene and/or ethyl-metal (e.g., Et2Zn or EtMgBr) as described herein
Figure imgf000033_0002
, wherein Z, M, X, and Y are as described in Formula I, Formula II, or Formula III. Certain embodiments of the invention provide a method for catalyzing a metathesis reaction, comprising contacting one or more reactant compounds with a catalyst compound or composition described herein (e.g., a compound of Formula III and/or a compound of Formula II). In certain embodiments, the method for catalyzing a metathesis reaction comprises contacting one or more reactant compounds with a compound of Formula III. In certain embodiments, the method for catalyzing a metathesis reaction comprises contacting one or more reactant compounds with a compound of Formula II. In certain embodiments, the method for catalyzing a metathesis reaction further comprises activating or converting a compound of Formula II into a compound of Formula III. For example, in certain embodiments, the method for catalyzing a metathesis reaction further comprises irradiating the catalyst compound or composition with light. In certain embodiments, the method further comprises irradiating the catalyst compound or composition with light prior to contacting one or more reactant compounds with the catalyst described herein (e.g., a compound of Formula III and/or a compound of Formula II). In certain embodiments, the method further comprises irradiating the catalyst compound or composition with light after contacting one or more reactant compounds with the catalyst described herein (e.g., a compound of Formula III and/or a compound of Formula II). In certain embodiments, the light comprises or consists of visible light. In certain embodiments, the light comprises or consists of blue light. In certain embodiments, the light comprises or consists of a wavelength range of about 380 to 750nm. In certain embodiments, the light comprises or consists of a wavelength range of about 385-720nm, 390-600nm, 395-530nm, 400-525nm, 405-520nm, 405-515nm, 405-510nm, 405 to 500nm, 410 to 490nm, or 420 to 480nm. In certain embodiments, the light is blue light comprising or consisting of a wavelength range of about 380-500nm, 390-470nm, or 400-450nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 520, 510, 500, 490, 480, 470, 460, 450, 445, 440, 430, 420, 410, 405, or 400nm. In certain embodiments, the blue light comprises or consists of a wavelength of 405, 410, 420, 430, 440, 450, or 460nm. In certain embodiments, the blue light comprises or consists of a wavelength that is less than about 520, 510, 500, 490, 480, 470, 460, 450, 445, 440, 430, 420, 410, 409, 408, 407, or 406nm. In certain embodiments, the blue light comprises or consists of a wavelength of about 450, or 405nm. In certain embodiments, light irradiation is provided by a light source emitting a light spectrum that comprises or consists of a wavelength range described herein (e.g., about 380 to 750nm). In certain embodiments, light irradiation is provided using a narrow band light source such as LED or laser. In certain embodiments, light irradiation is provided by a blue LED light source (e.g., 405nm, or 460nm). In certain embodiments, light irradiation is provided by a blue laser. The light source may be a light bulb, tube, strip, or array of light sources. In certain embodiments, the light source does not emit green, yellow, and/or red light. For example, in certain embodiments, the light source does not emit light with the wavelength range of about 530 to 750nm, 550 to 730nm, or 600 to 700nm. In certain embodiments, light irradiation is provided using a broad band light source, e.g., that may emit a continuous spectrum of light, such as extending from UV to near infrared such as about 300-1400 nm. In certain embodiments, the light is ambient light. In certain embodiments, light irradiation is provided using an incandescent or fluorescent light source. In certain embodiments, the light is sunlight. The light source brightness and/or wattage may vary to suit the requirements of reactions at different scales. For example, in certain embodiments, the light source may have a wattage of about 1, 10, 50, 100, 200, 400, 600, 800mW, or 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000W, or higher. In certain embodiments, the light source may have a wattage of about 1mW to 2000W, 60mW to 600W, or 100mW to 400W. In certain embodiments, the light source may have a brightness of about 1 to 100,000, 10 to 10,000, 100 to 3000, or 1000 to 5000 lumens. In certain embodiments, the compound of formula II is irradiated with light without heating (e.g., at room temperature such as at about 20-25 °C). In certain embodiments, the compound of formula II is irradiated with light with cooling at a temperature that is lower than room temperature. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is lower than 20, 15, 10, 5, 0, -5, -10, -20, -30, -40, -50, -60, -70, -80, -90, or -100°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is lower than -40, -50, -60, -70, -80, -90, or -100°C. In certain embodiments, the compound of formula II is irradiated with light at about 5- 20°C. In certain embodiments, the compound of formula II is irradiated with light at about 0- 4°C. In certain embodiments, the compound of formula II is irradiated with light at about 0 to - 90°C, -10 to -85°C, -20 to -80°C. In certain embodiments, the compound of formula II is irradiated with light at about -10, -20, -30, -40, -50, -60, -70, -80, or -90°C. In certain embodiments, the compound of formula II is irradiated with light at about -30 or -80°C. In certain embodiments, the compound of formula II is irradiated with light at about -40 to -90°C, -45 to -85°C, -50 to -80°C. In certain embodiments, the compound of formula II is irradiated with light with heating (e.g., to a temperature that is above room temperature). In certain embodiments, the compound of formula II is irradiated with light at about 30-50°C, or 35-45°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is about 30, 35, 40, 45, or 50°C. In certain embodiments, the compound of formula II is irradiated with light at a temperature that is at least about 30, 35, 40, 45, or 50°C. Although in certain situation, light irradiation (in particular, at high power) or close proximity with a light source may convey heat, heating as used herein only refers to temperature control provided by a temperature control apparatus or a heating source other than the light source. In certain embodiments, the compound of formula II is irradiated with light for about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23hrs, 1 day, 2 days, or longer. In certain embodiments, the compound of formula II is irradiated with light for about 0.5-16hrs, 1-12hrs, 1-9hrs, 1.5-8hrs, 2-6hrs, or 2-4hrs. In certain embodiments, the compound of formula II is irradiated with light for about 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 hrs. Methods for catalyzing metathesis reaction are known in the art and described herein. In addition, R Schrock, et al., Angew Chem Int Ed Engl.2003 Oct 6;42(38):4592-633. doi: 10.1002/anie.200300576. is incorporated by reference herein for all purposes. In certain embodiments, one reactant compound is contacted with the catalyst composition. In certain embodiments, two different reactant compounds (i.e., a first reactant compound and a second reactant compound) are contacted with the catalyst composition. In certain embodiments, a reactant compound is a compound comprising a C=C bond. In certain embodiments, the one or more reactant compounds are two different reactant compounds that each comprises a C=C bond. In certain embodiments, a reactant compound has one C=C bond. In certain embodiments, a reactant compound has two C=C bonds. In certain embodiments, a reactant compound has one C≡C bond. In certain embodiments, one or each reactant compound is independently an unsaturated, branched or unbranched, C2-C20 hydrocarbon chain, wherein one or more carbon of the hydrocarbon chain is optionally replaced with -O-, -N(Rs)-, -S-, divalent aryl (e.g.,-C6H4-) or heteroaryl, and wherein the hydrocarbon chain is optionally substituted on carbon with one or more substituents selected from the group consisting of halo, hydroxy, amino, mercapto, oxo (=O), and thioxo (=S), wherein Rs is H or alkyl (e.g., C1-C6). In certain embodiments, a reactant compound is an alkene compound. In certain embodiments, the alkene compound is a straight chain, branched or unbranched, or cyclic alkene compound of 2 to 20 carbon atoms comprising one or more double bond, and the alkene compound is optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, mercapto, oxo (=O), thioxo (=S), aryl, and heteroaryl. In certain embodiments, a reactant compound is a cyclic alkene (cycloalkene). In certain embodiments, the one or more reactant compounds are alkene compounds. In certain embodiments, the alkene compound is a C2-C20 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C18 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C16 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C14 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C12 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C10 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C8 alkene group. In certain embodiments, the reactant alkene compound is a C2-C6 alkene compound. In certain embodiments, the reactant alkene compound is a C2-C4 alkene compound. In certain embodiments, one reactant alkene compound is ethylene or propylene. In certain embodiments, the reactant alkene compound is optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, mercapto, oxo (=O), thioxo (=S), aryl, and heteroaryl. In certain embodiments, one reactant compound is an unsaturated fatty acid (e.g., monounsaturated or polyunsaturated C3-C26) or ester thereof. In certain embodiments, the reactant compound is an unsaturated C4-C24 or C6-C22 fatty acid or ester thereof. In certain embodiments, the reactant compound is an unsaturated C8-C20 or C10-C18 fatty acid or ester thereof. In certain embodiments, the method for catalyzing a metathesis reaction is conducted in the dark. In certain embodiments, the method for catalyzing a metathesis reaction is conducted with irradiation of light. In certain embodiments, the method for catalyzing a metathesis reaction further comprises heating the catalyst composition. In certain embodiments, the method further comprises heating the catalyst composition to a temperature that is higher than about 25 °C. In certain embodiments, the method for catalyzing a metathesis reaction further comprises heating the catalyst composition to about 30~130 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 40~120 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 50~110 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 60~105 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 70~100 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 80~90 °C. In certain embodiments, the method further comprises heating the catalyst composition to about 50 to 150oC, 60 to 140oC, 70 to 130oC, or 80 to 120oC. In certain embodiments, the method for catalyzing a metathesis reaction further comprises heating to at least about 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85oC. In certain embodiments, the method further comprises heating to about 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120oC. In certain embodiments, the method for catalyzing a metathesis reaction is conducted for at least 5, 10, 15, 30, 45 minutes, 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 36h, 48h, 72h or longer. Certain Definitions As used herein, the term “metathesis reaction” is described herein and known in the art and is given its ordinary meaning in the art and refers to a chemical reaction in which two reacting species exchange partners. In some embodiments, a metathesis reaction is performed in the presence of a transition-metal catalyst. In some cases, a byproduct of a metathesis reaction may be ethylene. A metathesis reaction may involve reaction between species comprising, for example, olefins and/or alkynes. Examples of different kinds of metathesis reactions include cross metathesis, ring-closing metathesis, ring-opening metathesis, acyclic diene metathesis, alkyne metathesis, enyne metathesis, olefin metathesis and the like. A metathesis reaction may occur between two substrates which are not joined by a bond (e.g., intermolecular metathesis reaction) or between two portions of a single substrate (e.g., intramolecular metathesis reaction). In some embodiments, two substrates of a metathesis reaction are identical. In some embodiments, a metathesis reaction is an ethenolysis reaction. The term "alkyl", by itself or as part of another substituent, means, unless otherwise stated, a straight or branched chain hydrocarbon radical, having the number of carbon atoms designated (i.e., C1-8 means one to eight carbons). Examples include (C1-C8)alkyl, (C2-C8)alkyl, (C1-C6)alkyl, (C2-C6)alkyl, (C1-C3)alkyl, and (C3-C6)alkyl. Examples of alkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, iso-butyl, sec-butyl, n-pentyl, n-hexyl, n- heptyl, n-octyl, and higher homologs and isomers. The term “aryl” as used herein refers to a single all carbon aromatic ring or a multiple condensed all carbon ring system wherein at least one of the rings is aromatic. For example, in certain embodiments, an aryl group has 6 to 20 carbon atoms, 6 to 14 carbon atoms, 6 to 12 carbon atoms, or 6 to 10 carbon atoms. Aryl includes a phenyl radical. Aryl also includes multiple condensed carbon ring systems (e.g., ring systems comprising 2, 3 or 4 rings) having about 9 to 20 carbon atoms in which at least one ring is aromatic and wherein the other rings may be aromatic or not aromatic (i.e., cycloalkyl. The rings of the multiple condensed ring system can be connected to each other via fused, spiro and bridged bonds when allowed by valency requirements. It is to be understood that the point of attachment of a multiple condensed ring system, as defined above, can be at any position of the ring system including an aromatic or a cycloalkyl portion of the ring. Non-limiting examples of aryl groups include, but are not limited to, phenyl, indenyl, indanyl, naphthyl, 1, 2, 3, 4-tetrahydronaphthyl, anthracenyl, and the like. The term “halo” or “halogen” refers to bromo, chloro, fluoro or iodo. In some embodiments, halogen refers to chloro or fluoro. The term “heteroaryl” as used herein refers to a single aromatic ring that has at least one atom other than carbon in the ring, wherein the atom is selected from the group consisting of oxygen, nitrogen and sulfur; “heteroaryl” also includes multiple condensed ring systems that have at least one such aromatic ring, which multiple condensed ring systems are further described below. Thus, “heteroaryl” includes single aromatic rings of from about 1 to 6 carbon atoms and about 1-4 heteroatoms selected from the group consisting of oxygen, nitrogen and sulfur. The sulfur and nitrogen atoms may also be present in an oxidized form provided the ring is aromatic. Exemplary heteroaryl ring systems include but are not limited to pyridyl, pyrimidinyl, oxazolyl or furyl. “Heteroaryl” also includes multiple condensed ring systems (e.g., ring systems comprising 2, 3 or 4 rings) wherein a heteroaryl group, as defined above, is condensed with one or more rings selected from cycloalkyl, aryl, heterocycle, and heteroaryl. It is to be understood that the point of attachment for a heteroaryl or heteroaryl multiple condensed ring system can be at any suitable atom of the heteroaryl or heteroaryl multiple condensed ring system including a carbon atom and a heteroatom (e.g., a nitrogen). Exemplary heteroaryls include but are not limited to pyridyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrazolyl, thienyl, indolyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, furyl, oxadiazolyl, thiadiazolyl, quinolyl, isoquinolyl, benzothiazolyl, benzoxazolyl, indazolyl, quinoxalyl, and quinazolyl. As used herein, the term "heteroatom" is meant to include oxygen (O), nitrogen (N), sulfur (S) and silicon (Si). Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., "Stereochemistry of Organic Compounds", John Wiley & Sons, Inc., New York, 1994. The compounds of the invention can contain asymmetric or chiral centers, and therefore exist in different stereoisomeric forms. It is intended that all stereoisomeric forms of the compounds of the invention, including but not limited to, diastereomers, enantiomers and atropisomers, as well as mixtures thereof such as racemic mixtures, form part of the present invention. Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L, or R and S, are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes d and l or (+) and (-) are employed to designate the sign of rotation of plane-polarized light by the compound, with (-) or 1 meaning that the compound is levorotatory. A compound prefixed with (+) or d is dextrorotatory. For a given chemical structure, these stereoisomers are identical except that they are mirror images of one another. A specific stereoisomer can also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture. A 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which can occur where there has been no stereoselection or stereospecificity in a chemical reaction or process. The terms "racemic mixture" and "racemate" refer to an equimolar mixture of two enantiomeric species, devoid of optical activity. It will be appreciated by those skilled in the art that certain compounds described herein have a chiral center may exist in and be isolated in optically active and racemic forms. Some compounds may exhibit polymorphism. It is to be understood that the present invention encompasses any racemic, optically-active, polymorphic, or stereoisomeric form, or mixtures thereof, of a compound of the invention, which possess the useful properties described herein, it being well known in the art how to prepare optically active forms (for example, by resolution of the racemic form by recrystallization techniques, by synthesis from optically-active starting materials, by chiral synthesis, or by chromatographic separation using a chiral stationary phase). When a bond in a compound formula herein is drawn in a non-stereochemical manner (e.g. flat), the atom to which the bond is attached includes all stereochemical possibilities. Certain embodiments of the invention will be illustrated in the following non-limiting Example. Example 1. Formation of Alkylidenes from Terminal Olefins via ^, ^'-Disubstituted Tungstacyclopentane Complexes Treatment of the tungstacyclopentane complex, W(NCPh3)(OSiPh3)2(C4H8), with propylene yields first a β-methyltungstacyclopentane complex (W(β-MeC4H7)) and then a trans-β,β'- dimethyltungstacyclopentane complex (W(β,β'-Me2C4H6)). W(β,β'-Me2C4H6) is consumed in a first order manner upon photolysis at 405 nm and 243 K to give primarily an alkylidene formed through ^ hydrogen abstraction. At room temperature ~20% of an isopropylidene complex is also formed through ring-contraction to give a α,α,β-trimethyltungstacyclobutane which loses propylene. A bicylic tungstacyclopentane complex - prepared by treating W(NCPh3)Cl2(OSiPh3)2 with two equivalents of BrMg(CH2)5CHCH2 - undergoes ~95% α hydrogen abstraction upon photolysis, while a β,β'-dipentyl tungstacyclopentane complex undergoes ~87% α hydrogen abstraction upon photolysis. An Eyring plot for consumption of W(β,β'-Me2C4H6) reveals that the apparent activation energy of only ~2.3 kcal mol-1. We propose that light promotes one electron from the HOMO that is comprised of both W-C bonds into a dxy orbital. "Metal-assisted" (through agostic interactions) H atom migrations then lead to either ring-contraction or (primarily) α hydrogen abstraction within the WC4 ring. These are the first reports of how W(VI) alkylidenes form from two terminal olefins and W(IV). For over 50 years an outstanding question in organometallic chemistry and catalysis has been how heterogeneous and homogeneous alkylidene complexes that are catalysts for olefin metathesis and that contain Mo, W, or Re are formed from olefins.1, 2 Recently we showed that d2 molybdenum or tungsten styrene complexes can be protonated slowly with dimethylanilinium to yield a mixture (~2:1) of styrene and phenethylidene complexes.3, 4 The intermediate is a cationic 1-phenethyl complex that can be deprotonated either at the α or the β position. A second method of preparing alkylidenes (in the absence of an acid) was found to consist of ring-contraction of unsubstituted d0 square pyramidal (SP) tungstacyclopentane complexes, W(NR)(OSiPh3)2(C4H8) (R = Ar = 2,6-i-Pr2C6H3 or R = CPh3),5 which are prepared from two equivalents of ethylene and a W(IV) complex. W(C4H8) complexes are thermally stable in solution in the dark, but under visible light the five-membered ring contracts to give a SP α methyl- substituted tungstacyclobutane complex (W(α-MeC3H5), eq 1),5 the trigonal bipyramidal (TBP) form of which is the key intermediate in olefin metathesis reactions.6 W(NAr)(OSiPh3)(OSisurf)(C4H8), formed through deposition of W(NAr)(OSiPh3)2(C4H8) on silica, also ring-contracts, photochemically or thermally, to give a catalyst that converts ethylene to propylene without forming butenes.7
Figure imgf000041_0001
W(C4H8) W(α-MeC3H5) W(C3H6) In this Example we report that β,β'-disubstituted tungstacyclopentane complexes can be prepared in the dark from olefins and they form alkylidenes upon irradiation primarily through a third mechanism, namely abstraction of a hydrogen atom from one α carbon atom in the tungstacyclopentane by the second α' carbon atom (Hα to Cα' migration), a variation of what has been called α hydrogen abstraction in dialkyls to give neopentylidene and neophylidene d0 Mo, W, and Re complexes, which has been known for almost 50 years.1, 2 Although α abstraction was considered in monocyclopentadienyl tantalacyclopentane complexes that are catalysts for catalytically dimerizing α olefins, the mechanism was found to consist of ring-contraction of the tantalacyclopentane to a tantalacyclobutane followed by rearrangement of that tantalacyclobutane to yield two dimers.8-13 Heating a solution of the unsubstituted tungstacyclopentane complex, W(NCPh3)(OSiPh3)2(C4H8)5 (W(C4H8)) in toluene-d8, under 1 atm of propylene in the dark at 100 °C produces first a β-methyl tungstacyclopentane complex, W(β-MeC4H7) (eq 2, two isomers). These complexes can be observed in 1H NMR spectra in yields as high as ~80%. According to
Figure imgf000042_0001
studies the β-methyl group in the major isomer (~65%) of W(β-MeC4H7) points "down", away from the imido ligand; in the minor isomer the methyl group points "up".
Figure imgf000042_0003
The reaction in eq 2 can be driven to >90% completion if ethylene is removed periodically. The two methyl doublets for trans-W(β,β'-Me2C4H6) are found at 0.85 and 0.75 ppm. Trans- W(β,β'-Me2C4H6) can be isolated in good yield (88%). Single crystal X-ray structural analysis (Fig 1) shows its geometrical parameters to be comparable to those of the unsubstituted SP complex,5 W(C4H8), except the W-C bond lengths in W(β,β'-Me2C4H6) (2.173, 2.163) are slightly shorter than those in W(C4H8) (2.222, 2.202) (>95% probability on the basis of +/- 3σ). Irradiation of a solution of W(β,β'-Me2C4H6) under molecular nitrogen at 405 nm in a modified J-Young NMR tube at 243 K using an LED optical fiber as the light source leads to its conversion (~89%) to primarily (~95%) the syn form of 1 (eq 3), along with ~5% 2 (eq 4). Compound 1 is formed when a hydrogen atom moves from an α carbon atom to an α' carbon atom (α hydrogen abstraction14). Compound 2 is formed when the TBP form of an unobservable α,α,β- trimethyl tungstacyclobutane complex formed through ring-contraction loses propylene (eq 4; see SI). The rate of disappearance of W(β,β'-Me2C4H6) is first order in W with k243 = 2.9 x 10-4 (R = 0.9997) s-1. At room temperature ~20% of 2 is formed. Addition of isobutene to the mixture converts all of 1 to 2 through metathesis. At room temperature the rate of disappearance of W(β,β'-Me2C4H6) is about half the rate of disappearance of W(C4H8) in the same photochemical reactor under identical conditions (Table 1).
Figure imgf000042_0002
Table 1. Photolyses at 405 nm and 298 K in toluene-d8. Compound 104 x k (s-1) Product(s) W(C4H8) 22 Contraction W(β,β'-Me2C4H6) 9.1 Abstraction ~80% W(C7H12) 5.5 Abstraction ~95% W(β,β'-pentyl2C4H6) 1.7 Abstraction ~87% Formation of 1 can be followed conveniently through observation of a multiplet for Hβ (eq 3) in its 1H NMR spectrum at ~3.75 ppm. Anti and (primarily) syn isomers are observed with Hα at 7.93 and 10.0 ppm, respectively (see SI). Variable temperature kinetic studies (Figure 2) between 243 and 298 K reveals that ΔH =2.3 kcal/mol and ΔS = 0.0 kcal/mol for consumption of W(β,β'- Me2C4H6), consistent with only a small thermal contribution to the activation energy of a photochemical process (vide infra). A reaction between W(C4H8) and 1-heptene in the dark under conditions similar to those shown in equation 1 results in formation of a β,β'-dipentyltungstacyclopentane, W(β,β'- (pentyl)2C4H6). A single crystal X-ray diffraction study (see SI) showed its geometry to be analogous to that for W(β,β'-Me2C4H6) (Fig 1). The rate constant for consumption of W(β,β'- (pentyl)2C4H6) at 298 K is 1.7 x10-4 s-1 and the yield of the alkylidene formed through α hydrogen abstraction is ~87%. The reaction between W(C4H8) and 1,6-heptadiene at 80 °C in the dark leads to formation of the symmetric 7-tungsta-bicyclo[3.3.0]octane complex, W(C7H12) (equation 5; isolated in 77% yield), which is found (Figure 2) to have a geometry analogous to that for isoelectronic Cp*TaCl2(C7H12) (Cp* = η5-C5Me5)15 in which the C5 ring points away from the Cp* ligand. Irradiation of W(C7H12) leads solely to formation of syn and anti alkylidenes in ~95% yield (10:1 ratio of syn to anti) through α hydrogen abstraction (eq 6).
Figure imgf000043_0001
The trend in the rate constants in Table 1 suggest that β,β'-disubstituted tungstacyclopentane complexes largely α abstract, and more slowly as the size of the substituents in the β and β' positions increases. We propose that conformations that are required for CHα and CHβ agostic interactions (vide infra) are likely to be more restricted for the larger and sterically more demanding and rigid tungstacyclopentanes, especially the 7-tungsta-bicyclo[3.3.0]octane derivative. Preliminary DFT calculations suggest that the LUMO in W(C4H8) and W(β,β'-Me2C4H6) is an empty dxy orbital that lies parallel to the plane of the two basal O atoms and two basal C atoms, while the HOMO is comprised of two W-C σ-bonds (see SI). Therefore this process can be described as a (σCWC)2(dxy)0 -> (σCWC)1(dxy)1 transition. The calculated absorption envelope for these transitions in W(C4H8) (Figure 3 top) and W(β,β'-Me2C4H6) (Figure 3 bottom) have maxima for the lowest energy excited state at ~380 nm. The fastest subsequent step in W(C4H8) is a shift of a hydrogen atom from a β-CH2 to the CH2 group next to it in the W(C4H8) ring, concurrent with formation of a W-C bond to give an ^-methyl-W(VI) tungstacyclobutane, W(α-MeC3H5). Because 1,2-hydrogen atom shifts in free hydrocarbon radicals have prohibitively high barriers,16 this "ring-contraction" must be "assisted" by the metal through CH agostic interactions.17, 18 (What was called an "agostic-assisted hydride shift" in a d0 tantalacyclooctane complex was calculated to be a relatively low energy process in theoretical studies44 concerning ethylene trimerization.) In W(β,β'-Me2C4H6) the fastest reaction is migration of a hydrogen atom from an α-CH2 group to the α'-CH2 group to form an alkylidene. Movement of a hydrogen atom from a β-CHMe group to an α'-CH2 group to give the (initial) ring-contraction product is an alternative at room temperature for the β,β'-dimethyl metallacyclopentane. We first proposed5 that unobservable TBP analogs of the SP tungstacyclopentane complexes reported here are the crucial intermediates for ring-contraction of W(C4H8), but we contend that a ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1 transition in the SP form of the tungstacyclopentane is a better proposal for both unsubsituted and β,β'-disubstituted tungstacyclopentanes. We propose that the photochemical step is not reversible and that hydrogen atom migrations after that step to give the initial photochemical product are fast and lead to both α abstraction and ring-contraction products (eq 3 and 4, respectively). It seems plausible that the rate of various H atom migrations in the tungstacyclobutene rings described here will depend on which configurations of the ring are favored. Migrations from a configurationally more accessible CH2 group are likely to be favored over migration from a monosubstituted (CHR) group in a tungstacyclopentane ring. Sensitivity of d0 transition metal alkyls to light has been noted for several decades.19-40 Light was found to accelerate α hydrogen abstraction in the first studies of α abstraction reactions in 14e SP CpTa(CH2-t-Bu)2Cl2 and Cp*Ta(CH2-t-Bu)2Cl2 complexes.21 α hydrogen abstraction reactions that give neopentylidene or neophylidene complexes in d0 Ta, Mo, W, and Re alkyl chemistry usually do not require light, but some α abstraction reactions do require light; formation of Re(NAr)2(CH2SiMe3)(CHSiMe3) from Re(NAr)2(CH2SiMe3)3 (with 366 nm light) is one example.32 Light has been known for some time to initiate other types of CH cleavage reactions (e.g., β hydrogen abstraction) in early metal alkyls, although virtually no detailed explanations of the role of light beyond promoting M-C and/or CH bond cleavage have appeared in the literature to our knowledge. The 14e tungstacyclopentane complexes discussed here are isostructural and isoelectronic with SP tantalum cyclopentadienyl complexes, including trans- Cp*Ta(CH2CHMeCHMeCH2)Cl2, which is in equilibrium with propylene and Cp*Ta(MeCH=CH2)Cl2.11, 13, 21 The Cp*Ta(CH2CHMeCHMeCH2)Cl2 ring contracts at 50°C to give an unobservable substituted tantalacyclobutane that does not lose an olefin, but rearranges to give 2,3-dimethyl-1-butene, the tail-to-tail or tt dimer (eq 7). These reactions are well-behaved in the dark, but accelerated in the light. No statement concerning a role for light in the catalytic dimerization of α olefins by cyclopentadienyl tantalacyclopentane complexes was provided.8-13
Figure imgf000045_0001
tt To our knowledge, this is the first report of formation of an alkylidene from terminal olefins in the absence of a source of "H" (from an external or internal source) and it happens to involve Hα abstraction within a β,β'-disubstituted metallacycloalkane ring formed from W(IV) and two terminal olefins.41-43 The ring-contraction and α abstraction products arise through competing "metal-assisted" H atom migrations (of Hα and Hβ) within a single photochemical intermediate. How and when a tungsten alkylidene might be formed in the dark from some substituted metallacyclopentane that is a variation of β,β'-disubstitution remains to be determined. α Hydrogen abstraction in square pyramidal tungstacyclopentane complexes now joins ring- contraction as a way metathesis catalysts can be formed and reformed from ethylene or terminal olefins in classical olefin metathesis systems in the absence of any alkylating agent.45 Metal reduction (to W(IV)) is no longer a problem, but a way to make alkylidenes. We expect to find that molybdenum chemistry46 will mimic much of the tungsten chemistry found so far, if we can find a way to observe mechanistic details before metathesis of olefins begins and obscures those details. An increased understanding of how alkylidenes form, and reform, from metallacyclopentane complexes ultimately could lead to significant improvements in the synthesis, design, and performance of modern Mo- or W-based homogeneous or heterogenous olefin metathesis catalysts. Supplementary Information (SI) of Example 1 General Procedures Unless otherwise noted, all manipulations were carried out using standard Schlenk or glovebox techniques under a N2 atmosphere. Tetrahydrofuran, diethyl ether, dichloromethane, and toluene were dried and deoxygenated by argon purge followed by passage through activated alumina in a solvent purification system followed by storage over 4 Å molecular sieves. Non-halogenated and non-nitrile containing solvents were tested with a standard purple solution of sodium benzophenone ketyl in THF to confirm effective oxygen and moisture removal prior to use. W(NCPh3)(OSiPh3)2(C4H8)[1] was prepared according to the published procedure. Ethylene Ultra High Purity was used as received from Airgas. Elemental analyses were performed at Atlantic Microlab, Inc., Norcross, GA. Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc., degassed, and dried over activated 4 Å molecular sieves for at least 24 h prior to use. NMR spectra were recorded on Bruker Avance 600 MHz, Bruker Avance 500 MHz and Bruker Avance 300 MHz spectrometers.1H and 13C chemical shifts are reported in ppm relative to tetramethylsilane using residual solvent as an internal standard.19F and 31P chemical shifts are reported in ppm relative to respectively fluorobenzene and H3PO4 as external standards. Irradiations with Blue LEDs were realized with 30 Blue 5050 SMD (nominal power 3.1 mW, on a strip), powered by a 12V DC power supply and with an inline DC dimmer. The fluorescent tube installed in the laboratory is Sylvania FO32/835/ECO. Emission spectra were measured with the spectrometer OceanOptics USB4000. UV/Vis spectra were recorded using a Cary 60 Agilent spectrophotometer. Experimental procedures and spectroscopic data Synthesis of W(NCPh3)(OSiPh3)2(C4H8) EtMgBr (3.0 M in Et2O, 0.29 mL, 0.881 mmol, 2.0 eq.) was added dropwise to a degassed solution of W(NCPh3)(OSiPh3)2Cl2(THF) (500 mg, 0.441 mmol, 1.0 eq.) in toluene (30 mL) under an atmosphere of ethylene (15 psi) at -78°C. The solution was left to warm to room temperature in the dark and stirred for another 2 hours (Caution: Do not seal the flask before the solution reached room temperature due to potential evaporation of condensed ethylene.) The mixture was concentrated to 10 mL and filtered through a pad of celite. The filtrate was evaporated, the yellow residue was triturated with pentane (2 x 10 mL) and Et2O (2 x 10 mL) and recrystallized from toluene at -30°C to obtain the compound in 56% yield (260 mg, 0.247 mmol) as yellow crystals. The crystals were of adequate quality for single crystal X-Ray diffraction. Synthesis of W(NCPh3)(OSiPh3)2(β,β'-Me2C4H6) A degassed solution of W(NCPh3)(OSiPh3)2(C4H8) (500 mg, 0.477 mmol) in toluene (30 mL) was stirred in a sealed 500 mL J. Young flask under an atmosphere of propylene (15 psi) at 80°C for 2 h in the dark. NMR spectroscopic analysis of an aliquot showed that a mixture of moderately photo-sensitive W(NCPh3)(OSiPh3)2(β-MeC4H7) isomers had formed which was characterized without further purification. All volatiles were removed in vacuo, the residue was redissolved in toluene (30 mL), the solution was degassed (2 freeze-pump-thaw cycles) and stirred under an atmosphere of propylene (15 psi) at 80°C for 2 h in the dark. The exchange of solvent and atmosphere as well as exposure to propylene was repeated one more time as described. After another 2 h of stirring at 80°C in the dark, the volatiles were removed in vacuo and the crude product was recrystallized from toluene at -30°C to obtain the title compound (260 mg, 0.247 mmol, XX% from two crops) as yellow crystals of adequate quality for single crystal X-ray structural analysis. Anal. Calcd for C61H57NO2Si2W: C, 68.08; H, 5.34; N, 1.30. Found: C, 67.97; H, 5.29; N, 1.41. W(NCPh3)(OSiPh3)2(β-MeC4H7) 1H NMR (600 MHz, PhMe-d8, 298 K, δ): 7.57 (m, o-CH of OSiPh3, 12H), 7.36 (m, o-CH of NCPh3, 6H), 7.16 (m, p-CH of OSiPh3, 6H), 7.06-7.03 (m, m-CH of OSiPh3, 12H), 7.01-6.99 (m, p-CH of NCPh3, 3H), 6.97-6.94 (m, m-CH of NCPh3, 6H), 3.36 (m, H-β’ of minor WMeC4H7, 1H), 2.89 (m, H-α’ of major WMeC4H7, 1H), 2.81 (m, H-β’ of major WMeC4H7, 1H), 2.71 (m, H-α’ of minor WMeC4H7, 1H), 2.59 (m, H-β of major WMeC4H7, 1H), 2.43 (m, H-α of minor WMeC4H7, 2H), 2.39 (m, H-α’ of minor WMeC4H7, 1H), 2.35 (m, H-α of major and H-β of minor WMeC4H7, 2H), 2.11 (m, H-α and H-α’ of major WMeC4H7, 2H), 1.97 (m, H-β’ of major WMeC4H7, 1H), 1.93 (m, H-β’ of minor WMeC4H7, 1H), 0.84 (d, Me of minor WMeC4H7, 3H), 0.74 (d, Me of major WMeC4H7, 3H). 13C NMR (151 MHz, C6D6, 298K, δ): 146.8 (s, C-ipso of NCPh3), 135.8 (s, C-ipso of OSiPh3), 135.8 (s, o-CH of OSiPh3), 130.1 (s, p-CH of OSiPh3), 130.0 (s, p-CH of OSiPh3), 129.3 (s, o-CH of NCPh3), 129.2 (s, o-CH of NCPh3), 128.3 (s, m-CH of NCPh3), 128.2 (s, m-CH of OSiPh3), 127.5 (s, p-CH of NCPh3), 88.8 (s, C-N), 88.7 (s, C-α of major WMeC4H7), 81.2 (s, C-α’ of major WMeC4H7), 73.6 (s, C-α of minor WMeC4H7), 64.6 (s, C-α’ of minor WMeC4H7), 46.1 (s, C-β’ of minor WMeC4H7), 44.2 (s, C-β of major WMeC4H7), 41.3 (s, C-β’ of major WMeC4H7), 41.1 (s, C-β of minor WMeC4H7), 26.8 (s, Me of major WMeC4H7), 24.9 (s, Me of minor WMeC4H7). W(NCPh3)(OSiPh3)2(β,β'-Me2C4H6) 1H NMR (600 MHz, C6D6, 298K, δ): 7.65 (m, o-CH of OSiPh3, 12H), 7.43 (m, o-CH of NCPh3, 6H), 7.18 (m, p-CH of OSiPh3, 6H), 7.09-7.06 (m, m-CH of OSiPh3, 12H), 7.03-7.00 (m, p-CH of NCPh3, 3H), 6.99-6.96 (m, m-CH of NCPh3, 6H), 2.99 (m, H-α of WMe2C4H6, 1H), 2.37 (m, H-α’ of WMe2C4H6, 1H), 2.19-2.16 (m, H-α’ of WMe2C4H6, 1H), 2.15-2.13 (m, H-α of WMe2C4H6, 1H), 1.99 (m, H-β’ of WMe2C4H6, 1H), 1.72 (m, H-β of WMe2C4H6, 1H), 0.86 (d, Me of WMe2C4H6, 3H), 0.75 (d, Me’ of WMe2C4H6, 3H). 13C NMR (151 MHz, C6D6, 298K, δ): 146.8 (s, C-ipso of NCPh3), 136.2 (s, C-ipso of OSiPh3), 135.8 (s, o-CH of OSiPh3), 130.2 (s, p-CH of OSiPh3), 130.1 (s, p-CH of OSiPh3), 129.3 (s, o-CH of NCPh3), 128.4 (s, m-CH of NCPh3), 128.3 (s, m-CH of OSiPh3), 127.5 (s, p-CH of NCPh3), 88.7 (s, C-N), 81.5 (s, 1JCW = 67.8 Hz, C-α’ of WMe2C4H6), 72.5 (s, 1JCW = 67.8 Hz, C-α of WMe2C4H6), 51.5 (s, C-β’ of WMe2C4H6), 46.9 (s, C-β of WMe2C4H6), 26.3 (s, Me of WMe2C4H6), 24.2 (s, Me’ of WMe2C4H6). Synthesis of W(NCPh3)(OSiPh3)2(C7H12) A degassed mixture of W(NCPh3)(OSiPh3)2(C4H8) (250 mg, 0.239 mmol, 1.0 eq.) and 1,6- heptadiene (23 mg, 0.239 mmol, 1.0 eq.) in toluene (10 mL) was stirred in a sealed 100 mL J. Young tube at 80°C for 3 h in the dark. All volatiles were removed in vacuo, the residue was redissolved in toluene (10 mL), the solution was degassed (2 freeze-pump-thaw cycles) and resubmitted to the reaction conditions. Removal of atmosphere and resubmission to the reaction conditions was repeated until monitoring of the reaction progress by 1H NMR spectroscopy showed complete conversion of starting material and intermediates. The volatiles were removed in vacuo and the crude product was recrystallized from toluene at -30°C to obtain the title compound (200 mg, 0.184 mmol, 77% from two crops) as a red solid. Anal. Calcd for C62H57NO2Si2W: C, 68.43; H, 5.28; N, 1.29. Found: C, 68.46; H, 5.44; N, 1.17. 1H NMR (600 MHz, C6D6, 298K, δ): 7.65 (m, o-CH of OSiPh3, 12H), 7.48 (m, o-CH of NCPh3, 6H), 7.18 (m, p-CH of OSiPh3, 6H), 7.09-7.06 (m, m-CH of OSiPh3, 12H), 7.02-6.98 (m, m-CH and p-CH of NCPh3, 9H), 3.01 (m, H-β of WC4H6Me2, 2H), 2.47-2.41 (m, H-α of WC4H6Me2, 4H), 1.57-1.51 (m, H-γ and H-δ of WC4H6Me2, 3H), 1.28 (m, H-δ of WC4H6Me2, 1H), 1.05-1.02 (m, H-γ of WC4H6Me2, 2H). 13C NMR (151 MHz, C6D6, 298K, δ): 147.2 (s, C-ipso of NCPh3), 136.0 (s, C-ipso of OSiPh3), 135.8 (s, o-CH of OSiPh3), 130.1 (s, p-CH of OSiPh3), 129.3 (s, o-CH of NCPh3), 128.4 (s, m-CH of NCPh3), 128.2 (s, m-CH of OSiPh3), 127.5 (s, p-CH of NCPh3), 88.6 (s, C-N), 76.2 (s, 1JCW = 68.4 Hz, C-α of WC7H12), 50.9 (s, C-β of WC7H12), 39.7 (s, C-γ of WC7H12), 26.1 (s, C-δ of WC7H12). Synthesis of W(NCPh3)(OSiPh3)2(β,β'-Pent2C4H6) A degassed mixture of W(NCPh3)(OSiPh3)2(C4H8) (250 mg, 0.239 mmol, 1.0 eq.) and 1-heptene (250 mg, 2.55 mmol, 11 eq.) in toluene (10 mL) was stirred in a sealed 100 mL J. Young tube at 80°C for 3 h in the dark. All volatiles were removed in vacuo, the residue was redissolved in toluene (10 mL) and 1-heptene (250 mg, 2.55 mmol, 11 eq.) was added. The mixture was degassed (2 freeze-pump-thaw cycles) and resubmitted to the reaction conditions. Removal of volatiles and resubmission to the reaction conditions as described was repeated until monitoring of the reaction progress by 1H NMR spectroscopy showed complete conversion of starting material and intermediates. The volatiles were removed in vacuo and the crude product was recrystallized from toluene at room temperature to obtain the title compound (190 mg, 0.162 mmol, 67% from two crops) as brown crystals. Single crystal X-ray structural analysis revealed excessive twinning in the sample and a significant degree of disorder mostly concerning the pentyl substituents of the Pent2C4H6 fragment. Anal. Calcd for C61H57NO2Si2W: C, 68.08; H, 5.34; N, 1.30. Found: C, 67.97; H, 5.29; N, 1.41. 1H NMR (600 MHz, C6D6, 298K, δ): 7.67 (m, o-CH of OSiPh3, 12H), 7.41 (m, o-CH of NCPh3, 6H), 7.19 (m, p-CH of OSiPh3, 6H), 7.10 (m, m-CH of OSiPh3, 12H), 7.04 (m, p-CH of NCPh3, 3H), 7.00 (m, m-CH of NCPh3, 6H), 2.96 (m, H-α of WPent2C4H6, 1H), 2.48 (m, H-α’ of WPent2C4H6, 1H), 2.06-2.02 (m, H-α, H-α’, H-β’, and H-δ of WPent2C4H6, 4H), 1.86 (m, H-β’ of WPent2C4H6, 1H), 1.57 (m, H-γ’ of WPent2C4H6, 1H), 1.48 (m, H-γ of WPent2C4H6, 1H), 1.32- 1.26 (m, WPent2C4H6, 5H), 1.17-1.11 (m, WPent2C4H6, 4H), 0.96-0.89 (m, WPent2C4H6, 9H), 0.73 (m, H-γ’ of WPent2C4H6, 1H). 13C NMR (151 MHz, C6D6, 298K, δ): 146.9 (s, C-ipso of NCPh3), 136.1 (s, C-ipso of OSiPh3), 135.8 (s, o-CH of both OSiPh3), 130.2 (s, p-CH of OSiPh3), 130.1 (s, p-CH of OSiPh3), 129.4 (s, o-CH of NCPh3), 128.4 (s, m-CH of NCPh3), 128.3 (s, m-CH of OSiPh3), 127.4 (s, p-CH of NCPh3), 88.6 (s, C-N), 78.4 (s, 1JCW = 64.8 Hz, C-α’ of WPent2C4H6), 71.0 (s, 1JCW = 66.0 Hz, C- α of WPent2C4H6), 56.0 (s, C-β’ of WPent2C4H6), 50.1 (s, C-β of WPent2C4H6), 40.7 (s, C-γ’ of WPent2C4H6), 38.1 (s, C-γ of WPent2C4H6), 32.7 (s, C-δ of WPent2C4H6), 32.6 (s, C-δ’ of WPent2C4H6), 28.0 (s, WPent2C4H6), 27.9 (s, WPent2C4H6), 23.4 (s, WPent2C4H6), 23.3 (s, WPent2C4H6), 14.5 (s, Me of WPent2C4H6), 14.5 (s, Me of WPent2C4H6). Photoinduced rearrangements General Procedure A solution of the β,β'-disubstituted tungstacyclopentane derivative (50.0 µmol) in toluene-d8 (0.50 mL) in a modified J. Young NMR tube was irradiated with 405 nm LED light (~50 mW) at a given temperature and the conversion of the starting material (SM) monitored by 1H NMR spectroscopy up to a conversion of >90%. The reaction was followed by integration of appropriately isolated signals. Plots of ln([SM]) vs. irradiation time were linear with R >= 0.95. Formation of W(NCPh3)(OSiPh3)2(CHCH(Me)CHMe2) by photolysis of W(NCPh3)(OSiPh3)2(β,β'-Me2C4H6) 1H NMR (600 MHz, C6D6, 298K, δ): 7.97 (d, W=CH-CH(CH3)-CH(CH3)2, 1H), 7.67 (m, o-CH of OSiPh3, 12H), 7.40 (m, o-CH of NCPh3, 6H), 7.18 (m, p-CH of OSiPh3, 6H), 7.13-7.10 (m, m- CH of OSiPh3, 12H), 7.02-6.99 (m, p-CH of NCPh3, 3H), 6.99-6.95 (m, m-CH of NCPh3, 6H), 3.82 (m, W=CH-CH(CH3)-CH(CH3)2, 1H), 1.20 (m, W=CH-CH(CH3)-CH(CH3)2, 1H), 0.70 (d, W=CH-CH(CH3)-CH(CH3)2, 3H), 0.65 (d, W=CH-CH(CH3)-CH(CH3)2, 3H), 0.63 (d, W=CH- CH(CH3)-CH(CH3)2, 3H). 13C NMR (151 MHz, C6D6, 298K, δ): 230.1 (s, 1JCW = 189 Hz, W=CH-CH(CH3)-CH(CH3)2), 147.5 (s, C-ipso of NCPh3), 136.3 (s, C-ipso of OSiPh3), 136.2 (s, C-ipso of OSiPh3), 135.7 (s, o- CH of OSiPh3), 135.6 (s, o-CH of OSiPh3), 130.1 (s, p-CH of OSiPh3), 129.3 (s, o-CH of NCPh3), 128.4 (s, m-CH of NCPh3), 128.2 (s, m-CH of OSiPh3), 127.2 (s, p-CH of NCPh3), 88.8 (s, C-N), 53.8 (s, W=CH-CH(CH3)-CH(CH3)2), 36.8 (s, W=CH-CH(CH3)-CH(CH3)2), 21.6 (s, W=CH- CH(CH3)-CH(CH3)2), 20.4 (s, W=CH-CH(CH3)-CH(CH3)2), 19.6 (s, W=CH-CH(CH3)- CH(CH3)2). NMR signature of isopropylidene fragment in W(NCPh3)(OSiPh3)2(CMe2) 1H NMR (600 MHz, C6D6, 298K, δ): 3.71 (s, W=C(CH3)2, 3H), 3.15 (s, W=C(CH3)2, 3H). 13C NMR (151 MHz, C6D6, 298K, δ): 233.7 (s, W=C(CH3)2), 34.9 (s, W=C(CH3)2), 20.0 (s, W=C(CH3)2). Photolysis of bicyclic derivative W(NCPh3)(OSiPh3)2(C7H12)
Figure imgf000050_0001
1H NMR (600 MHz, C6D6, 298K, δ): 8.09 (d, W(CH(C5H8)CH3, 1H), 7.67-7.64 (m, o-CH of OSiPh3, 12H), 7.40-7.37 (m, o-CH of NCPh3, 6H), 7.19 (m, p-CH of OSiPh3, 6H), 7.13-7.08 (m, m-CH of OSiPh3, 12H), 7.02-6.94 (m, p- and m-CH of NCPh3, 9H), 4.32 (m, H-β of W(CH(C5H8)CH3, 1H), 1.78 (m, H-ζ of W(CH(C5H8)CH3, 1H), 1.57 (m, H-γ of W(CH(C5H8)CH3, 1H), 1.50-1.43 (m, H-δ and H-ε of W(CH(C5H8)CH3, 2H), 1.29 (m, H-δ of W(CH(C5H8)CH3, 1H), 1.09 (m, H-ε of W(CH(C5H8)CH3, 1H), 0.95 (m, H-γ of W(CH(C5H8)CH3, 1H), 0.54 (m, W(CH(C5H8)CH3, 3H). 13C NMR (151 MHz, C6D6, 298K, δ): 226.7 (s, W(CH(C5H8)CH3)), 147.5 (s, C-ipso of NCPh3), 136.2 (s, C-ipso of OSiPh3), 135.7 (s, o-CH of OSiPh3), 130.1 (s, p-CH of OSiPh3), 129.3 (s, o- CH of NCPh3), 128.4 (s, m-CH of NCPh3), 128.2 (s, m-CH of OSiPh3), 127.2 (s, p-CH of NCPh3), 88.8 (s, C-N), 58.0 (s, C-β of W(CH(C5H8)CH3)), 41.2 (s, C-ζ of W(CH(C5H8)CH3)), 35.4 (s, C-γ of W(CH(C5H8)CH3)), 33.0 (s, C-ε of W(CH(C5H8)CH3)), 22.5 (s, C-δ of W(CH(C5H8)CH3)), 16.0 (s, W(CH(C5H8)CH3)). Computational details All DFT calculations were performed with the Gaussian 09 (c1) software package.[2] Ground state geometries were optimized using the B3LYP[3,4] functional augmented with the D3 version of Grimme’s empirical dispersion correction.[5] The SDD[6] basis set was used for tungsten and the TZVP[7,8] basis set for the other atoms. TD-DFT calculations were performed at the same level of theory for 6 excited states. X-Ray Crystallography W(NCPh3)(OSiPh3)2(β,β'-Me2C4H6) Single crystals suitable for X-ray diffraction were grown by slow cooling of a toluene solution. A yellow crystal (block, approximate dimensions 0.39 × 0.23 × 0.17 mm3) was placed onto the tip of a MiTeGen pin and mounted on a Bruker Venture D8 diffractometer equipped with a PhotonIII detector at 180.00 K. The data collection was carried out using Mo Ka radiation (l = 0.71073 Å, ImS micro-source) with a frame time of 5 seconds and a detector distance of 60 mm. A collection strategy was calculated and complete data to a resolution of 0.82 Å with a redundancy of 5.9 were collected. Three major twin domains were identified. The frames were integrated with the Bruker SAINT[9] software package using a narrow-frame algorithm to 0.82 Å resolution. Data were corrected for absorption effects using the multi-scan method (TWINABS).[10] Please refer to Table 1 for additional crystal and refinement information. The space group P-1 was determined based on intensity statistics and systematic absences. The structure was solved using the SHELX suite of programs[11,12] and refined using full-matrix least- squares on F2 within the OLEX2 suite.[13] An intrinsic phasing solution was calculated, which provided most non-hydrogen atoms from the E-map. Full-matrix least squares / difference Fourier cycles were performed, which located the remaining non-hydrogen atoms. All non-hydrogen atoms were refined with anisotropic displacement parameters. The hydrogen atoms were placed in ideal positions and refined as riding atoms with relative isotropic displacement parameters. The final full matrix least squares refinement converged to R1 = 0.0422 and wR2 = 0.0896 (F2, all data). The goodness-of-fit was 1.079. On the basis of the final model, the calculated density was 1.367 g/cm3 and F(000), 1146 e-. Disorder was modelled for a toluene molecule with 0.5 occupancy over a special position and for one of the ligands with two parts with 0.67 and 0.33 occupancies. Table 2. Crystal data and structure refinement for W(β,β'-Me2C4H6). Empirical formula C129 H122 N2 O4 Si4 W2 Formula weight 2244.34 Crystal color, shape, size yellow block, 0.39 × 0.23 × 0.17 mm3 Temperature 180.00 K Wavelength 0.71073 Å Crystal system, space group Triclinic, P-1 Unit cell dimensions a = 10.9828(8) Å a = 92.596(2)°. b = 11.8522(9) Å b = 92.217(2)°. c = 21.2554(13) Å g = 99.146(2)°. Volume 2725.9(3) Å3 Z 1 Density (calculated) 1.367 g/cm3 Absorption coefficient 2.207 mm-1 F(000) 1146 Data collection Diffractometer Bruker D8 Venture Theta range for data collection 2.349 to 25.349°. Index ranges -13<=h<=13, -14<=k<=14, 0<=l<=25 Reflections collected 142307 Independent reflections 10410 [Rint = 0.0943] Observed Reflections 8937 Completeness to theta = 25.242° 99.6 % Solution and Refinement Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.745263 and 0.383678 Solution Intrinsic methods Refinement method Full-matrix least-squares on F2 Weighting scheme w = [σ2Fo2+ AP2+ BP]-1, with P = (Fo2+ 2 Fc2)/3, A = 0.025, B = 9.85 Data / restraints / parameters 9947 / 257 / 648 Goodness-of-fit on F2 1.079 Final R indices [I>2σ(I)] R1 = 0.0422, wR2 = 0.0869 R indices (all data) R1 = 0.0498, wR2 = 0.0896 Largest diff. peak and hole 2.015 and -1.273 e.Å-3 Documents cited in Example 1: (1) Schrock, R. R.; Copéret, C. Formation of High-Oxidation-State Metal-Carbon Double Bonds. Organometallics 2017, 36, 1884-1892. (2) Ivin, K. J.; Mol, J. C. Olefin Metathesis and Metathesis Polymerization; Academic Press, 1997. (3) Liu, S.; Boudjelel, M.; Schrock, R. R.; Conley, M. P.; Tsay, C. Interconversion of Molybdenum or Tungsten d2 Styrene Complexes with d01-Phenethylidene Analogs. J. Am. Chem. Soc.2021, 143, 17209-17218. (4) Liu, S.; Conley, M. P.; Schrock, R. R. Synthesis of Mo(IV) para-Substituted Styrene Complexes and an Exploration of Their Conversion to 1-Phenethylidene Complexes. Organometallics 2022, 41, DOI: 10.1021/acs.organomet.1022c00473. (5) Boudjelel, M.; Riedel, R.; Schrock, R. R.; Conley, M. P.; Berges, A.; Carta, V. Tungstacyclopentane Ring-Contraction Yields Olefin Metathesis Catalysts. J. Am. Chem. Soc. 2022, 144, 10929–10942. (6) Schrock, R. R.; Buchmeiser, M. R.; Groos, J.; Benedikter, M. J. Group 6 High Oxidation State Alkylidene and Alkylidyne Complexes In Comp. Organomet. Chem. IV, Elsevier, 2022; pp 671-772. (7) Rodriguez, J.; Boudjelel, M.; Mueller, L. J.; Schrock, R. R.; Conley, M. P. Ring Contraction of a Tungstacyclopentane Supported on Silica: Direct Conversion of Ethylene to Propylene. J. Am. Chem. Soc.2022, 144, 18761-18765. (8) McLain, S. J.; Wood, C. D.; Schrock, R. R. Multiple Metal-Carbon Bonds.6. The Reaction of Niobium and Tantalum Neopentylidene Complexes with Simple Olefins: A Route to Metallocyclopentanes. J. Am. Chem. Soc.1977, 99, 3519-3520. (9) McLain, S. J.; Schrock, R. R. Selective Olefin Dimerization via Tantallocyclopentane Complexes. J. Am. Chem. Soc.1978, 100, 1315-1317. (10) McLain, S. J.; Wood, C. D.; Schrock, R. R. Preparation and Characterization of Tantalum(III) Olefin Complexes and Tantalum(V) Metallacyclopentane Complexes Made from Acyclic alpha Olefins. J. Am. Chem. Soc.1979, 101, 4558-4570. (11) McLain, S. J.; Sancho, J.; Schrock, R. R. Metallacyclopentane to Metallacyclobutane Ring Contraction. J. Am. Chem. Soc.1979, 101, 5451-5453. (12) McLain, S. J.; Sancho, J.; Schrock, R. R. Selective Dimerization of Monosubstituted ^- Olefins by Tantalacyclopentane Catalysts. J. Am. Chem. Soc.1980, 102, 5610-5618. (13) Schrock, R. R.; McLain, S. J.; Sancho, J. Tantalacyclopentane Complexes and their Role in the Catalytic Dimerization of Olefins. Pure and Appl. Chem.1980, 52, 729-732. (14) Schrock, R. R. An 'Alkylcarbene' Complex of Tantalum by Intramolecular ^-Hydrogen Abstraction. J. Am. Chem. Soc.1974, 96, 6796-6797. (15) Churchill, M. R.; Hollander, F. J.; Schrock, R. R.25. Crystal Structure of Bis( ^5- cyclopentadienyl)chloro(neopentylidene)tantalum. J. Am. Chem. Soc.1978, 100, 647-648. (16) Harding, L. W. Ab Initio Studies of (l,2)-Hydrogen Migrations in Open-Shell Hydrocarbons: Vinyl Radical, Ethyl Radical, and Triplet Methylcarbene. J. Am. Chem. Soc. 1981, 103, 7469-7475. (17) Brookhart, M.; Green, M. L. H.; Parkin, G. L. Agostic Interactions in transition metal compounds. Proc. Natl. Acad. Sci.2007, 104, 6908-6914. (18) Brookhart, M.; Green, M. L. H.; Wong, L. Carbon-Hydrogen-Transition Metal Bonds. Prog. Inorg. Chem.1988, 36, 1-65. (19) Schrock, R. R.; Parshall, G. W. ^-Alkyl and -Aryl Complexes of the Group 4-7 Transition Metals. Chem. Rev.1976, 76, 243-268. (20) Schrock, R. R. Preparation and Characterization of M(CH3)5 (M = Nb or Ta) and Ta(CH2C6H5)5 and Evidence for Decomposition by ^-Hydrogen Atom Abstraction. J. Organometal. Chem.1976, 122, 209-225. (21) Wood, C. D.; McLain, S. J.; Schrock, R. R. Multiple Metal Carbon Bonds.13. Preparation and Characterization of Monocyclopentadienyl Mononeopentylidene Complexes of Niobium and Tantalum Including the First Details of an ^-Abstraction Process. J. Am. Chem. Soc.1979, 101, 3210-3222. (22) Chiu, K. W.; Jones, R. A.; Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B.; Malik, K. M. A. Reactions of Hexamethyltungsten(VI) in the Presence of Trimethylphosphine - Synthesis of Methyl, Ethylidyne, Hydrido- Tungsten, Alkoxo-Tungsten, and Other Tungsten Compounds - X-Ray Crystal-Structures of Trans-Ethylidyne- (Methyl)Tetrakis(Trimethylphosphine)Tungsten(IV) and Trihydrido(Phenoxo)Tetrakis(Trimethylphosphine)Tungsten (IV). J. Chem. Soc., Dalton Trans.1981, 1204-1211. (23) Lockwood, M. A.; Clark, J. R.; Parkin, B. C.; Rothwell, I. P. Intramolecular activation of aromatic C-H bonds by tantalum alkylidene groups: evaluating 'cyclometallation resistant' aryloxide ligation. Chem. Commun.1996, 1973-1974. (24) Cai, S.; Hoffman, D. M.; Wierda, D. A. Rhenium(VII) Oxo-Alkyl Complexes: Reductive and ^-Elimination Reactions. Organometallics 1996, 15, 1023-1032. (25) Vilardo, J. S.; Lockwood, M. A.; Hanson, L. G.; Clark, J. R.; Parkin, B. C.; Fanwick, P. E.; Rothwell, I. P. Intramolecular activation of aromatic C-H bonds at tantalum(V) metal centers: evaluating cyclometallation 'resistant' and 'immune' aryloxide ligation. J. Chem. Soc., Dalton Trans.1997, 3353-3362. (26) de la Mata, F. J.; Gómez, J.; Royo, P. Synthesis and reactivity of cyclopentadienyl chloro, imido and alkylidene tungsten (VI) complexes. J. Organomet. Chem.1998, 564, 277-281. (27) Giannini, L.; Guillemot, G.; Solari, E.; Floriani, C.; Re, N.; Chiesi-Villa, A.; Rizzoli, C. Olefin Rearrangements Assisted by a Molecular Metal-Oxo Surface: The Chemistry of Calix[4]arene Tungsten(IV). J. Am. Chem. Soc.1999, 121, 2797-2807. (28) Fryzuk, M. D.; Johnson, S. A.; Rettig, S. J. Synthesis and structure of the tantalum trimethyl complex [P2N2]TaMe3 and its conversion to a tantalum methylidene species. Organometallics 1999, 18, 4059-4067. (29) Edwards, D. S.; Biondi, L. V.; Ziller, J. W.; Churchill, M. R.; Schrock, R. R. Rhenium(VII) Neopentylidene and Neopentylidyne Complexes and the X-ray Structure of Re(CCMe3)(CHCMe3)(C5H5N)2I2. Organometallics 1983, 2, 1505-1513. (30) Chamberlain, L. R.; Rothwell, I. P. Electronic absorption spectra and photochemical reactivity of group 5 metal alkyl compounds: photochemical ^-H hydrogen abstraction. J. Chem. Soc., Dalton Trans.1987, 163-167. (31) Bruno, J. W.; Kalinam, D. G.; Mintz, E. A.; Marks, T. J. Mechanistic Study of Photoinduced ^-Hydride Elimination. The Facile Photochemical Synthesis of Low-Valent Thorium and Uranium Organometallics. J. Am. Chem. Soc.1982, 104, 1860-1869. (32) Edwards, D. S.; Schrock, R. R. Rhenium(VII) Neopentylidene and Neopentylidyne Complexes. J. Am. Chem. Soc.1982, 104, 6806-6808. (33) Oskam, J. H.; Schrock, R. R. Rotational Isomers of Mo(VI) Alkylidene Complexes and Cis/Trans Polymer Structure: Investigations in Ring-Opening Metathesis Polymerization. J. Am. Chem. Soc.1993, 115, 11831-11845. (34) Toreki, R.; Schrock, R. R. Synthesis and Characterization of Re(VII) Alkylidene Alkylidyne Complexes of the Type Re(CR')(CHR')(OR)2 and Related Species. J. Am. Chem. Soc.1992, 114, 3367-3380. (35) Toreki, R.; Vaughan, G. A.; Schrock, R. R.; Davis, W. M. Metathetical Reactions of Re(VII) Alkylidene-Alkylidyne Complexes of the Type Re(CR')(CHR')[OCMe(CF3)2]2 (R' = CMe3 or CMe2Ph). J. Am. Chem. Soc.1993, 115, 127-137. (36) Stufkens, D. J.; van Outersterp, J. W. M.; Oskam, A.; Rossenaar, B. D.; Stor, G. J. The photochemical formation of organometallic radicals from a-diimine complexes having a metal- metal, metal-alkyl or metal-halide bond. Coord. Chem. Rev.1994, 132, 147-154. (37) Zhao, Y.; Yu, M.; Fu, X. Photo-cleavage of the cobalt–carbon bond: visible light-induced living radical polymerization mediated by organo-cobalt porphyrins. Chem. Comm.2013, 49, 5186-5188. (38) Schrauzer, G. N.; Grate, J. H. Sterically Induced, Spontaneous Co-C Bond Homolysis and ß-Elimination Reactions of Primary and Secondary Organocobalamins. J. Am. Chem. Soc. 1981, 103, 541-546. (39) Kress, J.; Wesolek, M.; Le, N. J. P.; Osborn, J. A. Molecular complexes for efficient metathesis of olefins. The oxo-ligand as catalyst-cocatalyst bridge and the nature of the active species. J. Chem. Soc., Chem. Commun.1981, (20), 1039-1040. (40) Poli, R. A journey into metal–carbon bond homolysis. Comptes Rendus Chimie 2021, 24, 147-175. (41) Blom, B.; Clayton, H.; Kilkenny, M.; Moss, J. R. Metallacycloalkanes - Synthesis, Structure and Reactivity of Medium to Large Ring Compounds Adv. Organomet. Chem.2006, 54, 149-205. (42) Zheng, F.; Sivaramakrishna, A.; Moss, J. R. Thermal Studies on Metallacycloalkanes. Coord. Chem. Rev.2007, 251, 2056-2071. (43) Dixon, J. T.; Green, M. J.; Hess, F. M.; Morgan, D. H. Advances in selective ethylene trimerization - a critical overview. J. Organomet. Chem.2004, 689, 3641-3668. (44) Yu, Z. X.; Houk, K. N. Why trimerization? Computational elucidation of the origin of selective trimerization of ethene catalyzed by [TaCl3(CH3)2] and an agostic-assisted hydride transfer mechanism. Angew. Chem. Int. Ed.2003, 42, 808-811. (45) Copéret, C.; Berkson, J. Z.; Chan, K. W.; de Jesus Silva, J.; Zhizhko, P. A. Olefin metathesis: what have we learned about homogeneous and heterogeneous catalysts from surface organometallic chemistry? Chem. Sci.2021, 12, 3092-3115. (46) Marinescu, S. C.; King, A. J.; Schrock, R. R.; Singh, R.; Müller, P.; Takase, M. K. Simple Molybdenum(IV) Olefin Complexes of the Type Mo(NR)(X)(Y)(olefin). Organometallics 2010, 29, 6816-6828. Example 2. Syntheses of Tungstabicycloalkanes from 1,6-Heptadiene or 1,7-Octadiene and Their Photochemical Conversions to Alkylidenes Addition of two equivalents of ethyl magnesium bromide or one of diethylzinc to W(NR)(OR')2Cl2 complexes (R = 2,6-i-Pr2C6H3 or C6H5, R' = SiPh3 or CMe2(CF3)) under ethylene gave the tungstacyclopentane complexes, W(NR)(OR')2(C4H8). After addition of 1,6-heptadiene or 1,7-octadiene these can be converted into 7-tungstabicylo[3.3.0]octane and 8- tungstabicylo[4.3.0]nonane complexes, respectively. Photolysis of the bicycles at 445 nm led to formation of terminal alkylidenes through an ^-hydrogen abstraction reaction that is proposed to involve promotion of one electron from the C-W-C HOMO into an empty dxy orbital. The bicyclic complexes can be prepared "directly" from the dialkoxide dichloride complexes without isolating any tungstacyclopentane intermediate using diethyl zinc as the reducing agent in the presence of 1,6-heptadiene or 1,7-octadiene. An analog of a 7-tungstabicylo[3.3.0]octane complex can be prepared from diallylaniline. Eight tungstacyclopentanes and one alkylidene derived through photolysis of a 7-tungstabicylo[4.3.0]nonane complex were characterized through single crystal X-ray diffraction studies. These results suggest that syntheses of tungstabicyclic complexes from dienes, and photolyses of them, may be a relatively general method of preparing metathesis-active alkylidene complexes from terminal olefins.
Figure imgf000055_0001
INTRODUCTION Long-standing questions concerning how heterogeneous and homogeneous alkylidene complexes that contain Mo, W, or Re are formed from olefins1 have recently begun to be answered. We first found that d2 molybdenum or tungsten styrene complexes can be protonated slowly with dimethylanilinium to yield a mixture (~2:1) of styrene and phenethylidene complexes.2, 3 More recently, we found that ^ ^ ^'-disubstituted tungstacyclopentane complexes can be formed from terminal olefins and that they rearrange in the absence of acid to alkylidenes through a photo-induced ring-contraction or (predominantly) ^ hydrogen abstraction, each of which is proposed to be assisted through CH agostic reactions in the ground or excited state of the 14e tungstacyclopentane complexes.4, 5, 6 If the 14e square pyramidal tungstacyclopentane complex, W(NCPh3)(OSiPh3)2(C4H8), is treated with 1,6-heptadiene, a 7- tungstabicyclo[3.3.0]octane complex, W(NCPh3)(OSiPh3)2(C7H12), is formed in high yield as a single isomer in which the C5H8 ring points away from the NCPh3 ligand (eq 1; W = W(NCPh3)(OSiPh3)2).6 Upon photolysis at 405 nm W(NCPh3)(OSiPh3)2(C7H12) undergoes only ^ abstraction to give the alkylidene, W(NCPh3)(CHC6H11)(OSiPh3)2 (eq 1). Ring-contraction does not compete with ^ abstraction in this case because of a reduced availability or mobility of the ^ hydrogens in a bicyclic complex compared to a ^ ^ ^'-dimethyltungstacyclopentane complex.6
Figure imgf000056_0001
We have proposed that the key event in photochemical ring-contractions or ^ hydrogen abstractions is promotion of an electron from a C-W-C molecular orbital (HOMO) to the empty dxy orbital (LUMO) that lies approximately parallel to the WO2C2 basal plane in the square pyramidal complex and perpendicular to the W=N triple bond. On the basis of preliminary DFT calculations we have propose this to be a ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1 transition. An absorption corresponding to this transition can be observed in UV/vis spectra at ~380 nm and the DFT calculations reproduce its (weak) intensity and position, but further details (e.g., excited state lifetime) are not yet known. It also is not known what happens in detail after this transition. It was proposed that accessibility of ^ or ^ protons toward migrations that lead to ring-contraction or ^ abstraction (eq 1) is determined by agostic CH ^ or CH ^ interactions. The only tungsten bicyclic complex that has been reported so far is W(NCPh3)(OSiPh3)2(C7H12).6 In this Example, we explore syntheses of alkylidenes from tungstacyclopentanes that are variations of W(NCPh3)(OSiPh3)2(C7H12). Among these variations are tungstacyclopentanes that contain phenylimido or trifluoro-t-butoxide ligands and bicyclic complexes prepared from 1,7- octadiene. Formation of tungstacyclopentane complexes from d2 complexes and terminal olefins is compatible with proposals that alkylidenes are formed from olefins in homogeneous7 and heterogeneous8 metathesis catalyst systems at d2 metal centers. The findings reported here suggest that formation of tungstacyclopentanes and alkylidenes from them could be relatively general. Elucidation of tungstacyclopentane chemistry and of thermally accessible reactions related to the photochemical reactions could potentially dramatically simplify syntheses of metathesis-active alkylidenes on a large scale and also lead to longer-lived catalyst activities through reformation of alkylidenes. RESULTS Synthesis of Phenylimido and Trifluoro-t-butoxide Unsubstituted Tungstacyclopentane Complexes The first monometallic tungstacyclopentane complex to be isolated and structurally characterized was W(NPh)(C4H8)[(TMSN)2C6H4] in which [(TMSN)2C6H4]2- is an o-phenylene- based bidentate diamido ligand;9 Mo(NPh)(C4H8)[(TMSN)2C6H4] was reported a few years later.10 No alkylidenes were reported to be formed from these metallacyclopentane complexes. Two equivalents of sodium triphenylsiloxide react with W(NPh)Cl4(Et2O)11 in a mixture of diethyl ether and THF to give red crystalline W(NPh)(OsiPh3)2Cl2(THF) in ~50% yield. Single crystals of a diethyl ether adduct can be grown from a mixture of dichloromethane and ether. Single crystal x-ray diffraction analysis of W(NPh)(OsiPh3)2Cl2(Et2O) showed it to contain diethyl ether bound trans to the imido ligand and triphenylsiloxide ligands trans to one another. Addition of two equivalents of ethyl magnesium bromide to a solution of W(NPh)(OsiPh3)2Cl2(THF) under ethylene led to formation of W(NPh)(OsiPh3)2(C4H8) (1; eq 2), which was isolated in ~40% yield. We presume that an ethylene complex is formed from a diethyl intermediate, and 1 through addition of ethylene to the ethylene complex. The proton NMR spectrum of 1 shows two resonances for the tungstacyclopentane protons at 298 K, but four resonances at 235 K (Fig 13), consistent with interconversion of “up” and “down” ^ protons and “up” and “down” ^ protons in a square pyramidal complex through an intramolecular five- coordinate Berry-type rearrangement via an intermediate that contains a plane of symmetry passing through the carbon atoms in a WC4 ring (on average). In the analogous W(NAr)(OsiPh3)2(C4H8) (Ar = 2,6-i-Pr2C6H3) complex4 the ^ and ^ proton resonances overlap to a significant degree but the temperature dependent proton NMR spectra are similar to what is shown for W(NPh)(OsiPh3)2(C4H8) in Fig 13. (See Table A1 for selected 13C chemical shifts for C ^ and C ^ atoms in tungstacyclopentanes.) Table A1. Chemical shifts (ppm) for C ^ atoms (with JCW values) and C ^ atoms in tungstacyclopentanes, alkylidenes, and one tungstacyclobutane (13) reported here. Compound δC ^ (ppm) δC ^ (ppm) JCW (Hz) 1 71.41 36.45 68.8 2aa 68.64 35.90 69.5 2ba 69.06 35.35 73.8 3 77.42 51.54 70.4 4 80.47, 68.26 54.58 70.1, 74.4 5 79.29, 66.96 54.68, 51.63 72.1, 74.0 6 70.58 46.90 68.1 59.53, 52.61 45.34, 36.12 68.6, 66.1 8 70.66 58.84 69.0 9 229.52 58.96 192.5 10 233.20 59.35 187.2 11 240.87 60.32 196.4 12 224.30 56.74 189.9 SP-13 45.31 22.92 43.4 TBP-13 98.70 -4.40 65.6 a Not isolated in pure form. SCXRD showed that 1 has a square pyramidal structure (Figure 14; ^ = 0.11) similar to that for the W(NAr)(OsiPh3)2(C4H8) analog.4 The W(C4H8) ring is puckered with W-C = 2.178(9) and 2.185(8). Variations include dialkoxides in which two OCMe2(CF3) ligands are present. Both W(NPh)(ORF3)2Cl2(THF) (ORF3 = OCMe2(CF3)) and W(NAr)(ORF3)2Cl2(THF) can be prepared in high yields in a manner similar to the synthesis of W(NPh)(OsiPh3)2Cl2(THF). Compounds 2a and 2b can also be prepared through addition of one equivalent of diethylzinc to W(NPh)(ORF3)2Cl2(THF) or W(NAr)(ORF3)2Cl2(THF) under ethylene (eq 2). Diethylzinc is potentially more desirable than EtMgBr because the risk of “overalkylation” to give complexes that contain more than two ethyl groups is lower. Diethylzinc is also relatively cheap and potentially complicating chloride/bromide is avoided. NR NR ZnEt2 RF3O W Cl RF3O W CH2 CH2 (3) RF3O Cl R F3 O CH2 CH2 THF R = Ph (2a) or Ar (2b) In 2a the proton NMR spectrum shows only two W(NPh)(C4H8) proton resonances at room temperature, while the spectrum of 2b shows four resonances at room temperature, consistent with a slower pseudorotation process in the case of W(NAr)(ORF3)2(C4H8), presumably due to the larger size of the NAr ligand versus the NPh ligand. Neither 2a nor 2b could be obtained in crystalline form, but they are formed in good yield according to NMR spectra of the crude product. They also have been used in situ for the synthesis of bicyclic tungstacyclopentanes in good yields (~80%; see next section). Synthesis of Bicyclic Tungstacyclopentanes We reported in Example 1 that treating the 14e square pyramidal tungstacyclopentane complex, W(NCPh3)(OsiPh3)2(C4H8), with 1,6-heptadiene leads to formation of a 7- tungstabicylo[3.3.0]octane complex, W(NCPh3)(OsiPh3)2(C7H12), in which the C5H8 ring points away from the NCPh3 ligand (eq 1). (Tantalabicycloalkane pentamethylcyclopentadienyl dichloride complexes formed from 1,6-heptadiene and 1,7-octadiene were reported some time ago12 and the 7-tantalabicyclo[3.3.0]octane complex formed from 1,6-heptadiene was crystallographically characterized.13, 14) Both ethylenes in a W(NR)(OsiPh3)2(C4H8) complex should be displaced efficiently by dienes and the resulting complexes should be the most stable ^ ^ ^’-disubstituted forms, as found in the TaCp* system. Heating a mixture of W(NAr)(OsiPh3)2(C4H8)4 (Ar = 2,6-diisopropylphenyl) and three equivalents of 1,6-heptadiene in the dark at 85 °C for 12 h led to formation of the 7- tungstabicyclo[3.3.0]octane complex, W(NAr)(OsiPh3)2(C7H12) (3), analogous to the compound shown in eq 1; it was isolated in 86% yield on a 100 mg scale. A proton NMR spectrum shows a 2:2:2:2:2:1:1 pattern for the protons in the bicycle between ~4 and ~1 ppm. A SCXRD showed 1 to be a square pyramid ( ^ = 0.09) with the five-membered ring pointing away from the imido ligand (Figure 15), analogous to what is found in the isolobal and isostructural Ta( ^5- C5Me5)Cl2(C7H12) complex13, 14 and in W(NCPh3)(OsiPh3)2(C7H12).6 The W-C ^ bond lengths are 2.177(9) and 2.182(9) Å, which are typical of W(VI)-C bonds in compounds of this type. The H ^ resonance is found at 2.73 ppm in proton NMR spectra and the C ^ at 77.2 ppm in 13C NMR spectra. (See Table A1 for a summary of 13C chemical shifts.) Compound 3 also can be prepared from W(NAr)(OsiPh3)2Cl2 under dinitrogen using diethylzinc in place of the Grignard reagent without isolating any intermediate; the yield is typically 84% yield on a 300 mg scale (eq 4). ZnEt2 W(NAr)(OSiPh3)2Cl2 1,6-heptadiene toluene
Figure imgf000060_0001
W = W(NAr)(OSiPh3)2; 3 ZnEt2 W(NAr)(OSiPh3)2Cl2 1,7-octadiene toluene
Figure imgf000060_0002
W(C8H14) (4) The reaction between W(NAr)(OsiPh3)2(C4H8) and 1,7-octadiene proceeds smoothly in the dark to yield the 8-tungstabicyclo[4.3.0.]nonane complex, W(NAr)(OsiPh3)2(C8H14) (4), as a single isomer; it was isolated in 73% yield on a 100 mg scale. A synthesis analogous to that shown in eq 5 leads to a 71% yield of 4 on a 300 mg scale. SCXRD shows 4 to be a square pyramid ( ^ = 0.15) with the six-membered ring joined to the WC4 ring in a transoid fashion (Figure 16). The C6 ring has a “chair” conformation with the W-C bonds (W-C = 1.128(16) and 1.129(16) Å) in equatorial positions in the C6 ring. The H ^ resonances are found at 2.94, 2.67, and 2.27 ppm in proton NMR spectra. (See Table A1 for 13C NMR data.) W(NAr)(ORF3)2(C8H14) (5; eq 5) can be prepared from W(NAr)(ORF3)2Cl2, diethylzinc, and 1,7-octadiene in a manner similar to syntheses shown in equations 4 and 5 and isolated in 78% yield. SCXRD shows the molecular geometry of 5 (Figure 17) to be analogous to that of 4 with ^ = 0.11. The phenylimido variation of 5, W(NPh)(ORF3)2(cis-C8H14) (6a), is also prepared readily, but it was found to have a cis ring junction with the C6 ring pointing down and away from the phenylimido ligand (Fig 18). NMR spectra of a sample of W(NPh)(ORF3)2(C8H14) in solution was found to be a mixture that contained 70% of the cis isomer (6a) and 30% of the trans isomer (6b). Heating this mixture converted it to an equilibrium mixture over a period of 24 h that contains 88% of the trans isomer (Figure 19 and eq 6); therefore the trans isomer is lower in energy by 1.3 kcal mol-1 at 50 °C in toluene-d8. The most logical method of interconversion is for an intermediate to be formed that contains a diene in which only one C=C bond is bound (eq 6). The C=C face through which the "free" olefin rebinds to W followed by formation of the WC4 ring determines whether the cis (6a) or the trans isomer (6b) is formed. The conditions for interconversion of isomers are roughly the same as the conditions required to form bicycles from unsubstituted tungstacyclopentanes, as one might expect. However, the structure of what is presumed to be a "bis-olefin" complex to a monoolefin complex intermediate (eq 6) is not known.
Figure imgf000061_0001
W(NPh)(ORF3)2(trans-C8H14) (6b), could be crystallized from the trans-rich mixture shown in Figure 19. It was found (Figure 20) to have a structure analogous to that of 5 (Figure 17) in which the two W-C bonds are in equatorial positions in the chair form of the six-membered ring. "Ring-down" and "ring-up" isomers can also interconvert, but on a faster time-scale of the order of a typical pseudorotation process. For example, a small amount (5-10%) of the ring-up isomer of W(NAr)(OSiPh3)2(C7H12) is found in a solution of the ring-down isomer in toluene-d8 at 238 K. At 298 K these minor resonances begin to broaden, consistent with interconversion of the ring-up and ring-down isomers through a pseudorotation process that is related to interconversion of up and down protons in W(NPh)(OSiPh3)2(C4H8), for example (Fig.13). The energy difference between these ring-up and ring-down isomers is also of the order of 1-2 kcal mol-1 in this case. Interconversion of ring-up and ring-down isomers of course does not require cleavage of the C ^-C ^ bond in the bicycle. Bicycles that contain O and N. Addition of (CH2=CHCH2)2O to W(NAr)(OSiPh3)2(C4H8) leads not to formation of a bicycle, but to formation of a ^-monosubstituted tungstacyclopentane (7) made from one ethylene and one of the two double bonds in diallylether. SCXRD shows that the ether oxygen coordinates to the metal (W-O = 2.327(7) Å) trans to the imido group to form a 16e pseudooctahedral complex (Figure 21). This result suggests that formation of a five-coordinate 14e is key to replacement of the second ethylene and replacement is "blocked" in 7 through formation of a 16e octahedral complex in which the ether oxygen does not readily dissociate. In contrast to diallylether, diallylaniline reacts with W(NAr)(OSiPh3)2(C4H8) to form a tungstabicyclic compound, W(NAr)(OSiPh3)2(C6H10NPh) (8; eq 7), analogous to W(NAr)(OSiPh3)2(C7H12) (3). An intermediate analogous to that shown in Figure 20 does not form, presumably because the nitrogen atom in (CH2=CHCH2)2NPh cannot bind as strongly to the metal as an oxygen. The 1H and 13C NMR features of W(C6H10NPh) are similar to those of 3. W = W(NAr)(OSiPh3)2 W(NAr)(OSiPh3)2(C6H10NPh) (8) UV/vis spectra, Photolyses, and Kinetics The weak absorption in the UV/vis spectra of W(NCPh3)(OSiPh3)2(C4H8) around 380 nm has been ascribed to a ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1 transition.6 UV/vis spectra of 3, 4, 5, and 6 all show similar weak transitions in their UV/vis spectra; the data are summarized in Table A2. The weak low energy tails in these absorptions extend to 450 nm and overlap with the 450 nm LED light emission (half height width ~30 nm ).4 Irradiation of W(NPh)(OSiPh3)2(C4H8) (1) in toluene-d8 with blue LEDs ( ^Max = 446 nm, ~93 mW power) under ethylene, was followed by 1H NMR for 30 min and gave a >90% conversion of 1 to propylene and W(NPh)(OSiPh3)2(C3H6) (13). The rate of consumption of 1 was first order in W with kobs = 3.5x10-3 s-1 (Table A3). Table A2. Summary of UV/vis spectra of four bicyclic complexes. ^max (nm) ^ (M-1 cm-1) W(NAr)(OSiPh3)2(C7H12) (3) 376 1833 W(NAr)(OSiPh3)2(C8H14) (4) 386 1877 W(NAr)(ORF3)2(C8H14) (5) 371 1444 W(NPh)(ORF3)2(C8H14) (6) 374 748 This result is essentially the same as that obtained for the consumption of W(NAr)(OSiPh3)2(C4H8) under ethylene to give propylene and square pyramidal W(NAr)(OSiPh3)2(C3H6).4 However, the W(NPh)(OSiPh3)2(C3H6) complex that is formed is a mixture of TBP and SP forms, according to proton and 13C NMR studies, with the TBP form predominating (~90%). According to HSQC{1H;13C} spectra, the characteristic resonances for the TBP form are found at 98.70 ppm (C ^ of TBP isomer) and -4.40 ppm (C ^ of TBP isomer), while the SP resonances are found at 45.31 ppm (C ^ of SP isomer) and 22.92 ppm (C ^ of SP isomer; Table A1). Only a trace of the SP isomer of W(NAr)(OSiPh3)2(C3H6) was found in NMR spectra at low temperatures.4 The rates of consumption of 1 and 4 in thf-d8 were close to rates of the reactions in tol-d8. No crystal of W(NPh)(OSiPh3)2(C3H6) suitable for an SCXRD study could be obtained. Table A3. Rate constants for consumption of tungstacyclopentane complexes at 298 K upon irradiation at 445 nm. solvent k (10-4 s-1) W(NPh)(OSiPh3)2(C4H8) (1) tol-d8 35 W(NPh)(OSiPh3)2(C4H8) (1) thf-d8 10 W(NAr)(OSiPh3)2(C7H12) (3) tol-d8 10 W(NAr)(OSiPh3)2(C8H14) (4) tol-d8 11 W(NAr)(OSiPh3)2(C8H14) (4) thf-d8 7.0 W(NAr)(ORF3)2(C8H14) (5) tol-d8 3.0 W(NPh)(ORF3)2(C8H14) (6) tol-d8 3.0 W(NAr)(OSiPh3)2(C6H10NPh) (8) tol-d8 8.0 Upon photolysis in a ~93 mW LED photoreactor (445 nm) 3, 4, 5, and 8 gave the expected alkylidenes (9, 10, 11, and 12, respectively; see Table 1 for 13C data) in high yields through ^ hydrogen abstraction. Compounds 9, 10, 11, and 12 have signature multiplet resonances for H ^ at 3.77, 3.79, 3.90, and 3.54 ppm, respectively. The doublet alkylidene H ^ resonances of those appear at 8.09, 7.98, 8.64 and 7.91 ppm for the major (syn) isomer. Using the same photoreactor (~93 mW at 445 nm), the observed rate constants for consumption of 3, 4, 5, and 8 in toluene-d8 were found to be 10, 11, 3.0, and 8.0 (units =10-4 s-1), respectively (Table A3), differ by a factor of three at most. Irradiation of 3 and 8 yielded alkylidenes 9 and 12, respectively (of the type shown in eq 8), while 4 and 5 yielded alkylidenes 10 and 11 of the type shown in equation 9. The structure of that formed from 5 was confirmed through SCXRD (Figure 21). It is the only structural confirmation of the proposed alkylidene formed through ^ abstraction. All are primarily the syn isomer in solution with the syn alkylidene H ^ doublet resonance upfield of that for the anti alkylidene (e.g., 7.98 ppm and 8.19 ppm, respectively, for 10 and 8.64 ppm and 8.91 ppm, respectively, for 11), as is typically the case for W alkylidenes of this type.
Figure imgf000063_0001
The rate of consumption of W(NPh)(ORF3)2(C8H14) (6) upon photolysis is not much different from the other photolyses that yield the alkylidenes shown in eq 9, but W(NPh)(ORF3)2(CHC7H13) complexes are susceptible to bimolecular alkylidene coupling to give various olefin isomers (eq 11) at a rate competitive with formation of the alkylidene itself. In contrast, W(NAr)(ORF3)2(CHC7H13) (Figure 22), is stable toward bimolecular decomposition under comparable concentrations (~0.01 mM), a fact that we ascribe to the larger size of the NAr ligand relative to the NPh ligand. (Tungsten alkylidenes that are smaller than neopentylidene and that are formed through reaction of a neopentylidene or neophylidene complex with an internal linear olefin have been found to couple to give W=W complexes.15, 16) The phenylimido ligand is simply too small to prevent bimolecular coupling at the concentrations found in these experiments. The metal-containing product or products formed through bimolecular decomposition of W(NPh)(ORF3)2(CHC7H13) was/were not identified. Photolysis of 6 under ethylene gives W(NPh)(ORF3)2(CHC7H13), which suggests that W(NPh)(ORF3)2(CHC7H13) is formed in the absence of ethylene.
Figure imgf000064_0001
DISCUSSION Sensitivity of d0 transition metal alkyls to light has been noted for several decades.17-38 Light was found to accelerate the background (dark) ^ hydrogen abstraction in the first studies of ^ abstraction reactions in 14e SP CpTa(CH2-t-Bu)2Cl2 and Cp*Ta(CH2-t-Bu)2Cl2 complexes.19 ^ Hydrogen abstraction reactions that give d0 alkylidene complexes from dialkyls usually do not require light, but some do require light (e.g., formation of Re(NAr)2(CH2SiMe3)(CHSiMe3) from Re(NAr)2(CH2SiMe3)3).30 Light has been known for some time to "promote" other types of CH cleavage reactions (e.g., ^ hydrogen abstraction) in early metal alkyls, but to our knowledge virtually no detailed explanations of the role of light have appeared in the literature. The evidence so far suggests that the photochemical transition that we are observing in the photolyzeable tungstacyclopentanes is a HOMO to LUMO promotion of one electron, i.e., ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1.6 Subseqent tungsten-assisted migration of a hydrogen atom selectively from H ^ to C' ^ ( ^ H abstraction) completes alkylidene formation. Ring contration (H ^ to C ^) takes place competitively (~20% at 298 K) in ^ ^ ^'-dimethyl tungstacyclopentanes, but not in the bicyclic analogs that have been examined so far. We suspect that tungstacyclopentanes with substitution patterns different from those described here may be susceptible to thermal rearrangements to alkylidenes, but it seems unlikely that the electronic transition can be reduced in energy to a thermally accessible value in ^ ^ ^'-disubstituted tungstacyclopentanes. It remains to be determined whether tungstacyclopentanes or tungstabicycloalkanes that do not fall into the category of SP ^ ^ ^'-disubstituted metallacyclopentanes can be converted into alkylidenes thermally in the absence of light. CONCLUSIONS We have shown that primarily, if not exclusively, ^ abstraction takes place upon photolysis (at ~450 nm) of 7-tungstabicylo[3.3.0]octane and 8-tungstabicylo[4.3.0]nonane complexes that contain trifluoro-t-butoxides, N(2,6-i-Pr2C6H3), or NPh ligands. Both cis and trans W(NPh)(ORF3)2(C8H14) complexes can be obtained from mixtures that contain primarily one or the other. An equilibrium mixture of the two (88% trans) can be obtained at 50 °C over a period of 24 h. The bicyclic complexes can be prepared from the unsubstituted tungstacyclopentane complexes, or more conveniently from dialkoxide dichloride complexes using diethyl zinc as the reducing agent in the presence of 1,6-heptadiene or 1,7-octadiene. An analog of a 7- tungstabicylo[3.3.0]octane complex can be prepared from diallylaniline, but not diallylether due to binding of the ether oxygen to the metal in a diallyether/ethylene intermediate ^-substituted tungstacyclopentane complex. In all cases an absorption in the vicinity of 380 nm that overlaps with the LED emission envelope is proposed to be due to promotion of one electron from the C- W-C HOMO to an empty dxy orbital, i.e., ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1. Metallacyclopentanes appear to have significant potential to be a general method of making alkylidenes from olefins and under some conditions could be a way of regenerating alkylidenes in metathesis systems thermally as well as photochemically. Experimental General. Unless otherwise noted, all manipulations were carried out using standard Schlenk or glovebox techniques under a N2 atmosphere. Tetrahydrofuran, diethyl ether, dichloromethane, and toluene were dried and deoxygenated by argon purge followed by passage through activated alumina in a solvent purification system followed by storage over 4 Å molecular sieves. Non- halogenated and non-nitrile containing solvents were tested with a standard purple solution of sodium benzophenone ketyl in THF to confirm effective oxygen and moisture removal prior to use. NaOSiPh3 was made from Ph3SiOH and NaH in Et2O at room temperature. EtMgBr was used as received from Sigma-Aldrich. Ethylene Ultra High Purity was used as received from Airgas. Elemental analyses were performed at Atlantic Microlab, Inc., Norcross, GA. Deuterated solvents were purchased from Cambridge Isotope Laboratories Inc., degassed, and dried over activated 4 Å molecular sieves for at least 24 h prior to use. NMR spectra were recorded on Bruker Avance 600 MHz, Bruker Avance 500 MHz and Bruker Avance 300 MHz spectrometers. 1H and 13C chemical shifts are reported in ppm relative to tetramethylsilane using residual solvent as an internal standard.19F and 31P chemical shifts are reported in ppm relative to respectively trichloro- fluoro-methane and H3PO4 as external standards. Irradiations with Blue LEDs were realized with 30 Blue 5050 SMD (on a strip with nominal power 3.1 mW each), powered by a 12V DC power supply with an inline DC dimmer. W(NPh)(OSiPh3)2Cl2(THF) W(NPh)Cl4(Et2O)11 (0.5 g, 1.02 mmol, 1 eq) was dissolved in a mixture of Et2O (20 mL) and THF (4 mL) in a vial and a stir bar was added. The vial was placed at -30°C in the fridge of the glovebox and left overnight. Then it was taken out from the fridge and NaOSiPh3 (0.62 g, 2.08 mmol, 2 eq) was added as a solid in portions over twenty minutes. The colour of the solution changed slowly from dark green to break red, accompanied by a precipitate formation after stirring at room temperature for 2 h. Then, the volatiles were removed under vacuum and the solid residue was washed with 5 mL of Et2O and 10 mL of pentane followed by extraction in dichloromethane. The filtrate was concentrated to 15 mL, added few drops of THF and stood at -30°C in order to obtain red crystalline compound in three corps, which were washed twice with cold CH2Cl2 (4 mL) and then once with pentane (6 mL) to afford W(NPh)(OSiPh3)2Cl2(THF) in ~45% yield (0.44 g). The red crystals appear as a pink powder when crushed. The benzene solution of this compound is orange. The single crystals suitable for diffraction can be grown from a concentrated solution of dichloromethane. Anal. Calcd for C52H57Cl2NO3Si2W: C, 57.03; H, 4.47; N, 1.45. Found: C, 56.75; H, 4.41; N, 1.47. W(NPh)(ORF3)2Cl2(THF). W(NPh)Cl4(Et2O) (0.5 g, 1.02 mmol, 1 eq) was dissolved in a mixture of Et2O (20 mL) and THF (5 mL) and a stir bar was added. In another vial LiOCMe2CF3 (273 mg, 2.04 mmol, 2 eq) was dissolved in Et2O (5 mL). Both the vials were left at -30°C overnight. Then the ether solution of LiOCMe2CF3 was added dropwise to W(NPh)Cl4(Et2O) solution over ten minutes. The color of the solution changed slowly from dark green to red, and finally to yellow after 2 h. This solution was filtered through a plug of Celite, the volatiles were removed in vacuo, and the solid residue was recrystallized from pentane at -30°C to afford golden yellow crystals in 85% yield (0.58 g). Anal. Calcd for C18H25Cl2F6NO3W: C, 32.17; H, 3.75; N, 2.08. Found: C, 32.18; H, 3.70; N, 2.10. W(NAr)(ORF3)2Cl2(THF). A solution of W(NAr)Cl4(Et2O) (0.5 g, 0.87 mmol, 1 eq) in a mixture of Et2O (20 mL) and THF (5 mL) at -30 °C was added to a solution of LiOCMe2CF3 (233 mg, 1.74 mmol, 2 eq) in Et2O (5 mL) at -30 °C dropwise over a period of ten minutes. The color of the solution changed slowly from dark green to red, and finally light yellow after stirring the solution at room temperature for 20 h. This solution was filtered through a plug of Celite, the volatiles were removed in vacuo and the solid was recrystallized from pentane at -30°C to afford golden yellow crystals in 90% yield (0.59 g). Anal. Calcd for C24H37Cl2F6NO3W: C, 38.12; H, 4.93; N, 1.85. Found: C, 38.33; H, 4.93; N, 1.85. W(NPh)(OSiPh3)2(C4H8) (1). W(NPh)(OSiPh3)2Cl2(THF) (600 mg, 0.62 mmol, 1 eq.) was dissolved in toluene (120 mL) in a 1L J. Young Flask. The solution was freeze pump thaw three times, and then 15 psi of ethylene was added. The solution was then cooled to -78°C and EtMgBr (3M in Et2O, 0.41 mL, 1.24 mmol, 2 eq.) was added dropwise. The solution was brought back to room temperature in the dark, and stirred for 12 hours (under ethylene). The solvents were removed from the reaction mixture and the dark yellow residue was extracted in pentane (60 mL) and the mixture was filtered. The filtrate was concentrated to 10 mL and stood at -30°C. Compound 2 was filtered off as a yellow solid in ~40% yield (220 mg, 0.25 mmol). The single crystals of adequate quality for X-Ray diffraction analysis were grown from a concentrated solution of diethyl ether. Compound 2 should be stored in the dark as it is sensitive to ambient light in solution. Anal. Calcd for C52H55NO2Si2W : C, 62.65; H, 4.92; N, 1.59. Found: C, 62.63; H, 4.86; N, 1.65. W(NPh)(ORF3)2(C4H8) (2a). W(NPh)(ORF3)2Cl2(THF)(600 mg, 0.89 mmol, 1 eq.) was dissolved in toluene (120 mL) in a 1L J. Young Flask. The solution was freezing pump thaw three times, and then 15 psi of ethylene was added. The solution was then cooled to -78°C and Et2Zn (1M in hexane, 0.89 mL, 0.89 mmol, 1 eq.) was added dropwise. The solution was brought back to room temperature in the dark and stirred overnight (under ethylene). The solvents were removed from the reaction mixture and the dark yellow residue was extracted in pentane (40 mL) and the mixture was filtered. The filtrate was concentrated to 5 mL and stood at -30°C. The desired product could not be obtained in crystalline form, only through removal of all solvents in vacuo. W(NAr)(ORF3)2(C4H8) (2b). W(NAr)(ORF3)2Cl2(THF)(600 mg, 0.79 mmol, 1 eq.) was dissolved in toluene (120 mL) in a 1L J. Young Flask. The solution was subject to three freeze-pump-thaw cycles, and then 15 psi of ethylene was added. The solution was then cooled to -78°C and Et2Zn (1M in hexane, 0.79 mL, 0.79 mmol, 1 eq.) was added dropwise. The solution was brought back to room temperature in the dark and stirred overnight (under ethylene). The solvents were removed from the reaction mixture in vacuo and the dark yellow residue was extracted in pentane (40 mL). The mixture was filtered and the filtrate was concentrated to 5 mL and stood at -30°C. The desired product could not be obtained as a crystalline solid. W(NAr)(OSiPh3)2(C7H12) (3) In a 100 mL J-Y flask, W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.104 mmol), 1,6-heptadiene (30 mg, 0.32 mmol, 3 equiv.) and toluene (10 mL) were added. Then the tube was heated with a stir bar in an oil bath at 85 °C and stirred for 12 h. Then, the volatiles were removed under vacuum and the solid residue was extracted in 10 mL of pentane. This solution was filtered through a plug of celite, and the filtrate was concentrated to 0.5 mL. Next, this pentane solution was kept at - 30°C to obtain yellow crystalline solid. This solid compound was washed once with cold pentane (0.2 mL) to afford W(NAr)(OSiPh3)2(C7H12) in ~86% yield (92 mg). The single crystals suitable for diffraction can be grown from a concentrated solution of n-pentane. Anal. Calcd for C55H59NO2Si2W: C, 65.66; H, 5.91; N, 1.39. Found: C, 65.81; H, 6.04; N, 1.52. W(NAr)(OSiPh3)2(C8H14) (4). In a 100 mL J-Y flask, W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.104 mmol), 1,7-octadiene (34 mg, 0.32 mmol, 3 equiv.) and toluene (10 mL) were added. Then the tube was heated with a stir bar in an oil bath at 85 °C and stirred for 12 h. Then, the volatiles were removed under vacuum and the solid residue was extracted in 10 mL of pentane. This solution was filtered through a plug of celite, and the filtrate was concentrated to 0.5 mL. Next, few drops of diethyl ether were added to this pentane solution and kept at -30°C to obtain yellow crystalline solid. This solid compound was washed twice with cold pentane (0.2 mL x 2) to afford W(NAr)(OSiPh3)2(C8H14) in ~73% yield (78 mg). The single crystals suitable for diffraction can be grown from a concentrated solution of diethyl ether. Anal. Calcd for C56H61NO2Si2W: C, 65.94; H, 6.03; N, 1.37. Found: C, 65.72; H, 6.22; N, 1.53. W(NAr)(ORF3)2(C8H14) (5). W(NAr)Cl2(ORF3)2(THF) (300 mg, 0.396 mmol, 1 equiv.), 1,7-octadiene (65 mg, 0.594 mmol, 1.5 equiv.) and toluene (60 mL) were added to a 500 mL J-Y flask. The reaction mixture was cooled to -78 °C and Et2Zn (1 equiv.) was added dropwise. The mixture was stirred overnight at room temperature and then heated in an oil bath at 80 °C and for 4 h. All volatiles were removed under vacuum and the solid residue was extracted with 10 mL of pentane. This solution was filtered through a plug of Celite, and the solvent was removed in vacuo. The residue was dissolved in ~ 1 mL diethyl ether and the solution was stored at -30°C to give a yellow crystalline solid. This solid compound was washed twice with cold ether (0.2 mL x 2). A second batch of crystals was obtained from the supernatant ether solution. The total overall yield of W(NAr)(ORF3)2(C8H14) was 78% (87 mg). Single crystals suitable for diffraction were grown from a concentrated solution of diethyl ether. Anal. Calcd for C28H43F6NO2W: C, 46.48; H, 5.99; N, 1.94. Found: C, 46.28; H, 5.94; N, 1.89. W(NPh)(ORF3)2(C8H14) (6) W(NPh)Cl2(ORF3)2(THF) (600 mg, 0.89 mmol, 1 eq.), 1,7-octadiene (294 mg, 2.67 mmol, 3 eq.) and toluene (120 mL) were added to a 500 mL JY flask. The reaction mixture was cooled to -78 °C and Et2Zn (0.89 mL, 1 eq.) was added dropwise. The mixture was stirred overnight at room temperature. The volatiles were removed under vacuum and the solid residue was extracted with 60 mL of pentane. This solution was filtered through a plug of Celite, and the volatiles were removed in vacuo. The residue was dissolved in pentane (3 mL) and this solution was kept at - 30°C to obtain yellow crystalline solid. This solid compound was washed once with cold pentane (0.2 mL) to afford W(NPh)(ORF3)2(C8H18) in 68% isolated yield (386 mg). Anal. Calcd for C22H31F6NO2W: C, 41.33; H, 4.89; N, 2.19. Found: C, 40.84; H, 4.73; N, 2.32. W(NAr)(OSiPh3)2[ ^-(CH2OCH2CH=CH2)C4H7] (7) W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.104 mmol), diallyl ether (30.6 mg, 0.31 mmol, 3 equiv.), and toluene (6 mL) were added to a 100 mL J-Y flask, and the flask was heated for 20 h at room temperature. The volatiles were removed under vacuum and the solid residue was extracted into 10 mL of pentane. This solution was filtered through a plug of Celite, and the solvent was removed in vacuo to afford a yellow foam. This residue was dissolved in 2 mL of diethyl ether and the solution was kept at -30°C to obtain yellow crystalline solid. This solid compound was washed once with cold diethyl ether (0.2 mL) to afford W(NAr)(OSiPh3)2(C7H12) in 46% yield (49 mg). Single crystals suitable for diffraction were grown from a concentrated solution of diethyl ether. Anal. Calcd for C56H61NO3Si2W: C, 64.92; H, 5.93; N, 1.35. Found: C, 64.91; H, 5.90; N, 1.39. W(NAr)(OSiPh3)2(C6H10NPh) (8). W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.1 mmol), N,N-diallylaniline (18 mg, 0.1 mmol, 1 equiv.) and toluene (10 mL) were added to a 100 mL J-Y flask, and the flask was heated at 80 °C for 6 h. The volatiles were removed under vacuum and the solid residue was extracted with 15 mL of pentane. This solution was filtered through a plug of Celite. The solvent was removed in vacuo to afford a yellow foam which was then dissolved in 2 mL of pentane and the solution was kept at -30°C. The desired compound oiled out from the pentane solution. The supernatant was decanted and the oily residue was exposed to vacuum to give a bright yellow foam solid W(NAr)(OSiPh3)2(C6H10N) in 61% yield (66 mg). Anal. Calcd for C60H62N2O2Si2W: C, 66.53; H, 5.77; N, 2.59. Found: C, 66.74; H, 5.78; N, 2.58. W(NAr)(CHC6H11)(OSiPh3)2 (9) Compound 1 (10 mg, 0.01 mmol) was dissolved in C6D6 (0.5 mL) in a J. Young NMR tube. The mixture was irradiated with LEDs ( ^Max = 446 nm, 93 mW). The reaction was followed by 1H NMR for 35 minutes with (>90% conversion of 1 to 4). A larger scale synthesis was carried out by dissolving compound 1 W(NAr)(OSiPh3)2(C7H12) (100 mg, 0.10 mmol), in toluene (10 mL) in a 100 mL J Y flask. A stir bar was added and the solution was then irradiated with blue LEDs ( ^Max = 446 nm, 93 mW) at room temperature. Irradiation was continued until all starting material was converted to product (monitored by 1H NMR spectroscopy). Then, the volatiles were removed under vacuum and the solid residue was extracted in 10 mL of pentane. This solution was filtered through a plug of Celite, and the filtrate was evaporated to dryness to give a yellow foam. Thks residue was dissolved in ~0.3 mL Et2O followed by the addition of ~0.5 mL of pentane and placed at −30 °C for few days. Yellow crystals were formed, which were washed with cold pentane twice, and dried under vacuum to afford W(NAr)(CHC6H11)(OSiPh3)2(4) in 61% yield (61 mg). Anal. Calcd for C28H43F6NO2W: C, 65.66; H, 5.91; N, 1.39. Found: C, 65.69; H, 5.92; N, 1.33. W(NAr)(CHC7H13)(OSiPh3)2 (10) Compound 2 (10 mg, 0.01 mmol) was dissolved in toluene-d8 (0.5 mL) in a J. Young NMR tube. The mixture was irradiated with Blue LEDs ( ^Max = 446 nm, 93 mW) and the reaction was followed by 1H NMR for 40 minutes (>92% conversion of 2 to 5). A larger scale synthesis of this compound was performed by dissolving compound 2 W(NAr)(OSiPh3)2(C7H12) (170 mg, 0.167 mmol), in toluene (15 mL) in a 100 mL J Y flask, which was then irradiated with blue LEDs ( ^Max = 446 nm, 93 mW). Irradiation was continued at room temperature until all starting material was converted to product (monitored by 1H NMR spectroscopy). The volatiles were removed in vacuo and the solid residue was extracted into ~10 mL of pentane. This solution was filtered through a plug of Celite, and the filtrate was evaporated to dryness to give a orange foam. This residue was dissolved in ~1.5 mL of pentane and the solution was placed at −30 °C for few days to give an orange crystalline solid which was then washed with cold pentane twice, and dried in vacuo to afford W(NAr)(CHC6H11)(OSiPh3)2(5) in 68% yield (116 mg). Anal. Calcd for C28H43F6NO2W: C, 65.94; H, 6.03; N, 1.37. Found: C, 65.93; H, 6.04; N, 1.32. W(NAr)(CHC7H13)(ORF3)2 (11) Compound 3 (8 mg, 0.01 mmol) was dissolved in C6D6 (0.5 mL) in a J. Young NMR tube. The mixture was irradiated with Blue LEDs ( ^Max = 446 nm, 93 mW). The reaction was followed by 1H NMR for 90 minutes with ~ 92% conversion of 3 to 6. A larger scale synthesis was performed by adding compound 2 W(NAr)(OSiPh3)2(C7H12) (90 mg, 0.124 mmol) to toluene (10 mL) in a 100 mL J Y flask. The solution was stirred and irradiated with blue LEDs ( ^Max = 446 nm, 93 mW). Irradiation was continued at room temperature until all starting material was converted to product (monitored by 1H NMR spectroscopy). The volatiles were removed in vacuo and the solid residue was extracted with ~10 mL of pentane. This mixture was filtered through a plug of Celite, and the filtrate was evaporated to dryness to give a orange solid. This solid was dissolved in ~0.2 mL of pentane and the solution was stood at −30 °C for few days. Yellow crystals formed, which were washed with cold pentane once, and dried in vacuo to afford W(NAr)(CHC7H13)(ORF3)2(6) in 72% yield (65 mg). Single crystals suitable for diffraction were grown from a concentrated solution in pentane. Anal. Calcd for C28H43F6NO2W: C, 46.48; H, 5.99; N, 1.94. Found: C, 45.36; H, 6.20; N, 1.91. W(NAr)(CHC6H11NPh)(OSiPh3)2 (12) W(NAr)(OSiPh3)2(C4H8) (100 mg, 0.1 mmol), N,N-diallylaniline (18 mg, 0.1 mmol, 1 equiv.) and toluene (10 mL) were added to a 100 mL J-Y flask, and the flask was heated at 80 °C for 6 h. The volatiles were removed under vacuum and the solid residue was extracted with 15 mL of pentane. This solution was filtered through a plug of Celite. The solvent was removed in vacuo to afford a yellow foam which was then dissolved in 2 mL of pentane and the solution was kept at -30°C. The desired compound oiled out from the pentane solution. The supernatant was decanted and the oily residue was exposed to vacuum to give a bright yellow foam solid W(NAr)(OSiPh3)2(C6H10N) in 61% yield (66 mg). Anal. Calcd for C60H62N2O2Si2W: C, 66.53; H, 5.77; N, 2.59. Found: Observation of W(NPh)(OSiPh3)2(C3H6) (13) Compound 2a (15 mg, 0.017 mmol) was dissolved in toluene-d8 (0.5 mL) in a J. Young NMR tube. The contents were subjected to a freeze-pump-thaw (FPT) procedure and 15 psi of C2H4 was then added. The mixture was irradiated with Blue LEDs ( ^Max = 446 nm, 93 mW). The reaction was followed by 1H NMR for 30 minutes to yield propylene and 13 (>90% conversion of 2a to 13). Observation of W(NPh)(OSiPh3)2(C3H6) Photolysis of 6 under ethylene as described for photolysis of 2a above also gives trigonal bipyramidal W(NPh)(ORF3)2(C3H6). References in Example 2: (1) Schrock, R. R.; Copéret, C. Formation of High-Oxidation-State Metal-Carbon Double Bonds. Organometallics 2017, 36, 1884-1892. (2) Liu, S.; Boudjelel, M.; Schrock, R. R.; Conley, M. P.; Tsay, C. Interconversion of Molybdenum or Tungsten d2 Styrene Complexes with d01-Phenethylidene Analogs. J. Am. Chem. Soc.2021, 143, 17209-17218. (3) Liu, S.; Conley, M. P.; Schrock, R. R. Synthesis of Mo(IV) para-Substituted Styrene Complexes and an Exploration of Their Conversion to 1-Phenethylidene Complexes. Organometallics 2022, 41, DOI: 10.1021/acs.organomet.1022c00473. (4) Boudjelel, M.; Riedel, R.; Schrock, R. R.; Conley, M. P.; Berges, A.; Carta, V. Tungstacyclopentane Ring-Contraction Yields Olefin Metathesis Catalysts. J. Am. Chem. Soc. 2022, 144, 10929–10942. (5) Rodriguez, J.; Boudjelel, M.; Mueller, L. J.; Schrock, R. R.; Conley, M. P. Ring Contraction of a Tungstacyclopentane Supported on Silica: Direct Conversion of Ethylene to Propylene. J. Am. Chem. Soc.2022, 144, 18761-18765. (6) Riedel, R.; Schrock, R. R.; Conley, M. P.; Carta, V. Formation of Alkylidenes From ^ ^ ^'- Disubstituted Tungstacyclopentane Complexes Through Metal-Assisted Hydrogen Atom Migrations. J. Am. Chem. Soc.2023, submitted. (7) Marinescu, S. C.; King, A. J.; Schrock, R. R.; Singh, R.; Müller, P.; Takase, M. K. Simple Molybdenum(IV) Olefin Complexes of the Type Mo(NR)(X)(Y)(olefin). Organometallics 2010, 29, 6816-6828. (8) Mougel, V.; Chan, K.-W.; Siddiqi, G.; Kawakita, K.; Nagae, H.; Tsurugi, H.; Mashima, K.; Safonova, O.; Copéret, C. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents. ACS Cent. Sci.2016, 2, 569-576. (9) Wang, S. Y. S.; VanderLende, D. D.; Abboud, K. A.; Boncella, J. M. Metallacyclopentane formation: A deactivation pathway for a tungsten(VI) alkylidene complex in olefin metathesis reactions. Organometallics 1998, 17, 2628-2635. (10) Ison, E. A.; Abboud, K. A.; Boncella, J. M. Synthesis and reactivity of molybdenum imido diamido metallacyclopentenes and metallacyclopentadienes and the mechanism of ethylene exchange with metallacyclopentane complexes. Organometallics 2006, 25, 1557-1564. (11) Pedersen, S. F.; Schrock, R. R. Preparation of Tungsten(VI) Phenylimido Alkyl and Alkylidene Complexes. J. Am. Chem. Soc.1982, 104, 7483-7491. (12) Smith, S.; McLain, S. J.; Schrock, R. R.53. Tantallabicyloalkane Complexes and their Use as Catalysts for the Cyclization of a,w-Dienes. J. Organometal. Chem.1980, 202, 269-277. (13) Churchill, M. R.; Youngs, W. J. Discovery of an "Opened-Envelope" Conformation for the TaC4 Ring in Tantalacyclopentane Complexes. Crystal and Molecular Structures of Ta( ^5- C5Me5)(C4H8)Cl2 and Ta( ^5-C5Me5)(C7H12)Cl2. Inorg. Chem.1980, 19, 3106-3112. (14) Churchill, M. R.; Youngs, W. J. X-ray Crystallographic Results on Tantallacyclopentane Complexes Derived from Ethylene and 1,6-Heptadiene: Ta( ^5-C5Me5)(C4H8)Cl2 and Ta( ^5- C5Me5)(C7H12)Cl2. J. Am. Chem. Soc.1979, 101, 6462-6463. (15) Lopez, L. P. H.; Schrock, R. R.410. "Formation of Dimers That Contain Unbridged W(IV)/W(IV) Double Bonds". J. Am. Chem. Soc.2004, 126, 9526-9527. (16) Lopez, L. P. H.; Schrock, R. R.; Müller, P.431. "Dimers that Contain Unbridged W(IV)/W(IV) Double Bonds". Organometallics 2006, 25, 1978-1986. (17) Schrock, R. R.; Parshall, G. W. sigma-Alkyl and -Aryl Complexes of the Group 4-7 Transition Metals. Chem. Rev.1976, 76, 243-268. (18) Schrock, R. R. Preparation and Characterization of M(CH3)5 (M = Nb or Ta) and Ta(CH2C6H5)5 and Evidence for Decomposition by alpha-Hydrogen Atom Abstraction. J. Organometal. Chem.1976, 122, 209-225. (19) Wood, C. D.; McLain, S. J.; Schrock, R. R. Multiple Metal Carbon Bonds.13. Preparation and Characterization of Monocyclopentadienyl Mononeopentylidene Complexes of Niobium and Tantalum Including the First Details of an alpha-Abstraction Process. J. Am. Chem. Soc.1979, 101, 3210-3222. (20) Chiu, K. W.; Jones, R. A.; Wilkinson, G.; Galas, A. M. R.; Hursthouse, M. B.; Malik, K. M. A. Reactions of Hexamethyltungsten(VI) in the Presence of Trimethylphosphine - Synthesis of Methyl, Ethylidyne, Hydrido- Tungsten, Alkoxo-Tungsten, and Other Tungsten Compounds - X-Ray Crystal-Structures of Trans-Ethylidyne- (Methyl)Tetrakis(Trimethylphosphine)Tungsten(IV) and Trihydrido- (Phenoxo)Tetrakis(Trimethylphosphine)Tungsten(IV). J. Chem. Soc., Dalton Trans.1981, 1204-1211. (21) Lockwood, M. A.; Clark, J. R.; Parkin, B. C.; Rothwell, I. P. Intramolecular activation of aromatic C-H bonds by tantalum alkylidene groups: evaluating 'cyclometallation resistant' aryloxide ligation. Chem. Commun.1996, 1973-1974. (22) Cai, S.; Hoffman, D. M.; Wierda, D. A. Rhenium(VII) Oxo-Alkyl Complexes: Reductive and a-Elimination Reactions. Organometallics 1996, 15, 1023-1032. (23) Vilardo, J. S.; Lockwood, M. A.; Hanson, L. G.; Clark, J. R.; Parkin, B. C.; Fanwick, P. E.; Rothwell, I. P. Intramolecular activation of aromatic C-H bonds at tantalum(V) metal centers: evaluating cyclometallation 'resistant' and 'immune' aryloxide ligation. J. Chem. Soc., Dalton Trans.1997, 3353-3362. (24) de la Mata, F. J.; Gómez, J.; Royo, P. Synthesis and reactivity of cyclopentadienyl chloro, imido and alkylidene tungsten (VI) complexes. J. Organomet. Chem.1998, 564, 277-281. (25) Giannini, L.; Guillemot, G.; Solari, E.; Floriani, C.; Re, N.; Chiesi-Villa, A.; Rizzoli, C. Olefin Rearrangements Assisted by a Molecular Metal-Oxo Surface: The Chemistry of Calix[4]arene Tungsten(IV). J. Am. Chem. Soc.1999, 121, 2797-2807. (26) Fryzuk, M. D.; Johnson, S. A.; Rettig, S. J. Synthesis and structure of the tantalum trimethyl complex [P2N2]TaMe3 and its conversion to a tantalum methylidene species. Organometallics 1999, 18, 4059-4067. (27) Edwards, D. S.; Biondi, L. V.; Ziller, J. W.; Churchill, M. R.; Schrock, R. R. Rhenium(VII) Neopentylidene and Neopentylidyne Complexes and the X-ray Structure of Re(CCMe3)(CHCMe3)(C5H5N)2I2. Organometallics 1983, 2, 1505-1513. (28) Chamberlain, L. R.; Rothwell, I. P. Electronic absorption spectra and photochemical reactivity of group 5 metal alkyl compounds: photochemical ^-H hydrogen abstraction. J. Chem. Soc., Dalton Trans.1987, 163-167. (29) Bruno, J. W.; Kalinam, D. G.; Mintz, E. A.; Marks, T. J. Mechanistic Study of Photoinduced ^-Hydride Elimination. The Facile Photochemical Synthesis of Low-Valent Thorium and Uranium Organometallics. J. Am. Chem. Soc.1982, 104, 1860-1869. (30) Edwards, D. S.; Schrock, R. R. Rhenium(VII) Neopentylidene and Neopentylidyne Complexes. J. Am. Chem. Soc.1982, 104, 6806-6808. (31) Oskam, J. H.; Schrock, R. R. Rotational Isomers of Mo(VI) Alkylidene Complexes and Cis/Trans Polymer Structure: Investigations in Ring-Opening Metathesis Polymerization. J. Am. Chem. Soc.1993, 115, 11831-11845. (32) Toreki, R.; Schrock, R. R. Synthesis and Characterization of Re(VII) Alkylidene Alkylidyne Complexes of the Type Re(CR')(CHR')(OR)2 and Related Species. J. Am. Chem. Soc.1992, 114, 3367-3380. (33) Toreki, R.; Vaughan, G. A.; Schrock, R. R.; Davis, W. M. Metathetical Reactions of Re(VII) Alkylidene-Alkylidyne Complexes of the Type Re(CR')(CHR')[OCMe(CF3)2]2 (R' = CMe3 or CMe2Ph). J. Am. Chem. Soc.1993, 115, 127-137. (34) Stufkens, D. J.; van Outersterp, J. W. M.; Oskam, A.; Rossenaar, B. D.; Stor, G. J. The photochemical formation of organometallic radicals from a-diimine complexes having a metal- metal, metal-alkyl or metal-halide bond. Coord. Chem. Rev.1994, 132, 147-154. (35) Zhao, Y.; Yu, M.; Fu, X. Photo-cleavage of the cobalt–carbon bond: visible light-induced living radical polymerization mediated by organo-cobalt porphyrins. Chem. Comm.2013, 49, 5186-5188. (36) Schrauzer, G. N.; Grate, J. H. Sterically Induced, Spontaneous Co-C Bond Homolysis and ß-Elimination Reactions of Primary and Secondary Organocobalamins. J. Am. Chem. Soc.1981, 103, 541-546. (37) Kress, J.; Wesolek, M.; Le, N. J. P.; Osborn, J. A. Molecular complexes for efficient metathesis of olefins. The oxo-ligand as catalyst-cocatalyst bridge and the nature of the active species. J. Chem. Soc., Chem. Commun.1981, (20), 1039-1040. (38) Poli, R. A journey into metal–carbon bond homolysis. Comptes Rendus Chimie 2021, 24, 147-175. Example 3. Formation of a Metathesis-Active Molybdenum Alkylidene from a Molybdacyclopentane The addition of 1,7-octadiene to Mo(NAr)(OSiPh3)2(CH2CH2) in the dark in an open vial under nitrogen leads to formation of the "5,6-molybdabicyclopentane" complex, Mo(NAr)(OSiPh3)2(trans-5,6-C8H14). Irradiation of Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) with 450 nm LED light leads to formation of an alkylidene, primarily the syn- Mo(NAr)(OSiPh3)2(trans-CHC7H3) isomer, through a light-induced ^ hydrogen abstraction reaction. Both Mo(NAr)(OSiPh3)2(5,6-C8H14) and Mo(NAr)(OSiPh3)2(CHC7H3) have been characterized through single crystal X-ray studies, although the crystal of the latter was a mixture of the four possible co-crystallized syn, anti, cis, and trans isomers. Attempts to carry out similar chemistry with 1,6-heptadiene allowed observation of Mo(NAr)(OSiPh3)2(cis-5,5-C7H12) in solution, but these studies are compromised by formation of ethylene and cyclohexene.
Figure imgf000074_0001
Mo= Mo(NAr)(OSiPh3)2 (Ar = 2,6-i-Pr2C6H3) There might be three mechanisms for forming metathesis-active Mo or W complexes from olefins. One is a proton-catalyzed rearrangement of an olefin to an alkylidene (and vice versa) via a cationic alkyl, which has been demonstrated for both Mo and W styrene complexes.1 The second and third both involve rearrangements of tungstacyclopentanes. We have shown (Scheme 1) that d0 tungstacyclopentane complexes can form alkylidene complexes either through ring- contraction (1 to 3) or ^ hydrogen abstraction (1 to 2). These processes are initiated through a light-induced (~400 nm) ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1 transition in the SP form of the tungstacyclopentane followed by rapid hydrogen atom migrations within the WC4 ring that are proposed to be promoted through agostic CH ^ or CH ^ interactions in some preferred configurations of the ring in the excited state. When the tungstacyclopentane is formed from 1,7- octadiene, a bicyclic complex is formed whose photolysis yields only an alkylidene through ^ hydrogen abstraction (equation 1).
Figure imgf000075_0001
It seems likely that molybdenum will behave like tungsten in some circumstances, but to our knowledge the only isolable four-coordinate molybdacyclopentane complexes analogous to tungsten imido bisalkoxide complexes such as the one shown in Scheme 1 are Mo(NAr)(OSiPh3)2(C4H8)2 and Mo(NPh)[(TMSN)2C6H4](C4H8).3 Some likely problems with forming molybdacyclopentane complexes, especially substituted ones, are that molybdacyclopentanes are likely to lose an olefin to form Mo(IV) olefin complexes more readily than tungstacyclopentanes, and secondly, that metathesis reactions could outcompete formation of molybdacyclopentanes and complicate their identification or isolation. A third problem is that terminal olefins might be isomerized to internal olefins by Mo(NR)(OR')2(olefin) complexes, presumably via an allyl hydride intermediate. This mechanism of olefin isomerization is a relative of "chain running" that is well-known in early metal alkyl chemistry. In this Example we show that all three of the above possible complications can be largely avoided when a bicyclic molybdacyclopentane complex is made from 1,7-octadiene and an alkylidene prepared through ^ hydrogen abstraction. To our knowledge this is the first time that a mechanism of forming a molybdenum alkylidene from an olefin in the absence of a source of H (e.g., external acid1) has been documented. + 1,7-octadiene The addition of 1.5 equiv of 1,7-octadiene to Mo(NAr)(OSiPh3)2(CH2CH2) (Mo(C2H4)) in the dark in an open vial under nitrogen leads to formation of the 5,6-bicycle, Mo(NAr)(OSiPh3)2(5,6- C8H14) (4), which was isolated as orange crystals in 57% yield (eq 2). The intermediate is likely to be that shown in equation 2, but details as to how a MC4 ring forms from a bis olefin complex are not known. The proton NMR spectrum of 4 is analogous to that for W(NAr)(OSiPh3)2(trans- 5,6-C8H14), except the ^ proton resonances in the bicycle are not resolved at 22 °C as they are in W(NAr)(OSiPh3)2(trans-5,6-C8H14). At -33 °C the four ^ proton resonances in the spectrum of 4 appear between 2.5 and 3.3 ppm (see Figure 23); other resonances can be identified through proton/proton correlations. In the 13C NMR spectrum the two ^ carbon resonances are found at v and w, and the two ^ carbon resonances at x and y ppm. The fluxional process that interconverts the four ^ ring protons (and others pairwise) in the proton NMR spectrum can be ascribed to a Berry-type five-coordinate rearrangement that consists of the bicyclic ring "flipping over" on the proton NMR timescale (~100 s-1), but not the 13C NMR timescale. Any exchange of free 1,7- octadiene with that in the form of the molybdacycle would take place on a significantly slower time-scale. In solution there are resonances for what may be Mo(NAr)(OSiPh3)2(cis-5,6-C8H14), but so far the amount of this isomer is too small to confirm that proposal. After three days at room temperature in solution ~25% of Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) has decomposed and cyclohexene, Mo(NAr)(OSiPh3)2(C4H8), and Mo(NAr)(OSiPh3)2(C2H4) are formed in what appears to be a metathesis ring-closing of 1,7-octadiene. But exactly how "free" 1,7-octadiene is formed, if that is the case, is not clear at this stage. A SCXRD of a crystal grown from a pentane solution showed it to be approximately a 1:1 mixture of Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) and Mo(NAr)(OSiPh3)2(cis-5,6-C8H14). The structure is understandably highly disordered (R1 = 3.53%, wR2 = 8.92 %) so the distances and angles in each are not as accurate as they should be and are not discussed, but finding can be relied upon. Other crystals obtained under other conditions are likely to have different ratios of the two compounds in a given crystal. Irradiation of Mo(NAr)(OSiPh3)2(5,6-C8H14) in C6D6 with ~450 nm LED light yields a mixture that contains a mixture of four terminal alkylidenes, consistent with formation of syn and anti isomers of both Mo(NAr)(OSiPh3)2(trans-5,6-C8H14) and Mo(NAr)(OSiPh3)2(cis-5,6-C8H14). We presume that the highest percentage component is formed from Mo(NAr)(OSiPh3)2(trans-5,6- C8H14) and has the syn conformation. A trace of a methylene complex is observed with a resonance at ~11.5 ppm. A SCXRD study of a crystal obtained from a pentane solution of the mixture of alkylidenes was found to be the syn isomer of the alkylidene derived from Mo(NAr)(OSiPh3)2(trans-5,6- C8H14), i.e., syn-Mo(NAr)(OSiPh3)2(trans-CHC7H13). The rate of consumption of Mo(NAr)(OSiPh3)2(5,6-C8H14) in C6D6 under 450 nm LED light was found to be ~25% of the rate of consumption of the analogous tungsten complex. We presume that ^ abstraction takes place after a rate-limiting light-induced ( ^CWC)2(dxy)0 -> ( ^CWC)1(dxy)1 transition and that an agostic CH ^ interaction facilitates the migration of H ^ to C' ^ ^ Attempts to make a 5,5 bicyclic complex through the reaction of 1,6-heptadiene to Mo(NAr)(OSiPh3)2(CH2CH2) in the dark in an open vial leads to a mixture that contains Mo(NAr)(OSiPh3)2(cis-5,5-C7H12), according to alpha proton resonances at x and y, as found for W(NAr)(OSiPh3)2(cis-5,5-C7H12), and for which a single crystal X-ray structure shows that the C5 ring points away from the NAr group. Only two alpha proton resonances are observed at 22 °C because the isomer in which the C5 ring points toward the NAr group is not accessible (>2 kcal higher in energy). However, this synthesis is more compromised by formation of ethylene and cyclopentene. We conclude that a molybdenum alkylidene can be formed from a molybdacyclopentane through a light-induced ^ abstraction. We also have to conclude, through a comparison with the analogous tungstacyclopentane chemistry, that ring-contraction of molybdacyclopentanes is also an option in some cases, e.g., the unsubstituted molybdacyclopentane. If olefin isomerization is also considered, molybdacyclopentanes with a variety of possible substitution patterns could form in small amounts that may thermally ring-contract or alpha abstract. Complications due to metathesis reactions therefore increase the complexity of the system, and mechanistic studies become more challenging. References in Example 3 (1) Liu, S.; Boudjelel, M.; Schrock, R. R.; Conley, M. P.; Tsay, C. Interconversion of Molybdenum or Tungsten d2 Styrene Complexes with d01-Phenethylidene Analogs. J. Am. Chem. Soc.2021, 143, 17209-17218. (2) Marinescu, S. C.; King, A. J.; Schrock, R. R.; Singh, R.; Müller, P.; Takase, M. K. Simple Molybdenum(IV) Olefin Complexes of the Type Mo(NR)(X)(Y)(olefin). Organometallics 2010, 29, 6816-6828. (3) Ison, E. A.; Abboud, K. A.; Boncella, J. M. Synthesis and reactivity of molybdenum imido diamido metallacyclopentenes and metallacyclopentadienes and the mechanism of ethylene exchange with metallacyclopentane complexes. Organometallics 2006, 25, 1557-1564. DOI: 10.1021/om050280x. All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The present disclosure has been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Claims

CLAIMS What is claimed is: 1. A compound of Formula II or Formula III
Figure imgf000079_0001
wherein M is molybdenum (Mo) or tungsten (W); the two R groups are each independently alkyl, or the two R groups taken together with the intervening carbon atoms form a ring A, wherein one carbon atom of the ring A is optionally replaced with -(NRe)-; wherein the two R groups or the ring is each independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, alkoxy, alkanoyl, alkanoyloxy, alkoxycarbonyl, aryl, and heteroaryl; Z is O, or NRa; X and Y are each independently ORb, N(Rc)2, or heteroaryl; Ra is alkyl, adamantyl, or aryl; Rb is alkyl, aryl, or Si(Rd)3; Rc is alkyl, or aryl; Rd is aryl; Re is alkyl, or aryl; and wherein each aryl of Ra, Rb, Rc, Rd, Re and R, and each heteroaryl of R, X and Y is independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, and (C1-C6) alkyl optionally substituted with one or more halo; wherein each alkyl of Ra, Rb, Rc, and Re is independently, optionally substituted with one or more substituents selected from the group consisting of halo, hydroxy, amino, aryl, and heteroaryl, wherein the aryl or heteroaryl is optionally substituted with one or more halo, hydroxy, or amino.
2. The compound of claim 1, wherein the compound has structure of Formula II.
3. The compound of claim 1, wherein the compound has structure of Formula III.
4. The compound of any one of claims 1-3, wherein the two R groups are in trans- configuration.
5. The compound of claim 4, wherein the compound has structure of Formula IIa’ or Formula IIa’’
Figure imgf000080_0001
.
6. The compound of claim 1, wherein the compound has structure of Formula IIIsyn or Formula IIIanti
Figure imgf000080_0002
Figure imgf000080_0004
Figure imgf000080_0003
.
7. The compound of claim 3, wherein the compound has structure of Formula IIb7
Figure imgf000080_0005
wherein Xa is -CH2- or -NRe-.
8. The compound of any one of claims 1-7, wherein the two R groups are each independently (C1-C10) alkyl.
9. The compound of any one of claims 1-8, wherein the two R groups are each independently (C1-C8) alkyl.
10. The compound of any one of claims 1-9, wherein the two R groups are each independently (C1-C6) alkyl.
11. The compound of any one of claims 1-10, wherein the two R groups are both methyl.
12. The compound of any one of claims 1-10, wherein the two R groups are not simultaneously methyl.
13. The compound of any one of claims 1-10, wherein the two R groups are both ethyl, propyl, butyl, pentyl, hexyl, heptanyl, or octanyl.
14. The compound of any one of claims 1-10, wherein the two R groups are both ethyl, 1- propyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptanyl, or 1-octanyl.
15. The compound of any one of claims 1-10, wherein the two R groups are both 1-pentyl.
16. The compound of any one of claims 1-2 and 4-5, wherein the compound is
Figure imgf000081_0001
.
17. The compound of any one of claims 1-2 and 4-5, wherein the compound is
Figure imgf000081_0002
18. The compound of any one of claims 1, 3-4 and 6-7, wherein the compound is
.
19. The compound of any one of claims 1, 3-4 and 6-7, wherein the compound is
Figure imgf000082_0001
.
20. The compound of any one of claims 1-7, wherein the two R groups taken together with the intervening carbon atoms form a ring A.
21. The compound of claim 20, wherein the compound has structure of Formula IIb
Figure imgf000082_0002
.
22. The compound of claim 20, wherein the compound has structure of Formula IIIb
Figure imgf000082_0003
.
23. The compound of any one of claims 21-22, wherein ring A is a (C3-C10) cycloalkane ring.
24. The compound of any one of claims 21-22, wherein ring A is a (C3-C4) cycloalkane ring.
25. The compound of any one of claims 21-22, wherein ring A is a (C5-C6) cycloalkane ring.
26. The compound of any one of claims 21-22, wherein ring A is not a (C5-C6) cycloalkane ring.
27. The compound of any one of claims 21-22, wherein ring A is a (C7-C10) cycloalkane ring.
28. The compound of any one of claims 21-22, wherein ring A is a (C8-C9) cycloalkane ring.
29. The compound of any one of claims 1-3, wherein the two R groups are in cis- configuration.
30. The compound of any one of claims 1-2, and 29, wherein the compound is
Figure imgf000083_0001
.
31. The compound of any one of claims 1-2, and 4-5, wherein the compound is
Figure imgf000083_0002
wherein Ar is 2,6-i-Pr2C6H3.
32. The compound of any one of claims 1, 3, 6-7 and 29, wherein the compound is
Figure imgf000083_0003
.
33. The compound of any one of claims 1, 3, 4-5, and 6-7, wherein the compound is
Figure imgf000083_0004
wherein Ar is 2,6-i-Pr2C6H3.
34. The compound of any one of claims 1-15 and 20-29, wherein M is tungsten.
35. The compound of any one of claims 1-15 and 20-29, wherein M is molybdenum.
36. The compound of any one of claims 1-15 and 20-29, wherein Z is O.
37. The compound of any one of claims 1-15 and 20-29, wherein Z is NRa.
38. The compound of any one of claims 1-15 and 20-29, wherein Ra is 2,6-diisopropylphenyl (2,6-i-Pr2C6H3).
39. The compound of any one of claims 1-15 and 20-29, X and Y are each independently heteroaryl, or ORb.
40. The compound of any one of claims 1-15 and 20-29, X and Y are each independently ORb.
41. The compound of any one of claims 1-15 and 20-29, X and Y are each OSi(Ph)3.
42. The compound of claim 1, 2, 4, 5, 6, 7, or 29, wherein the compound has structure of
Figure imgf000084_0001
wherein Ra is CPh3, or optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
43. The compound of claim 1, 3, 4, 6, 7, or 29, wherein the compound has structure of
Figure imgf000085_0001
wherein Ra is CPh3, or optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
44. The compound of claim 1, wherein the compound is a compound of ,
Figure imgf000086_0001
wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
45. The compound of claim 2, provided the compound is not a compound of wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
46. The compound of claim 3, provided the compound is not a compound of ,
Figure imgf000087_0001
wherein Ar is optionally substituted aryl (e.g., 2,6-i-Pr2C6H3).
47. A catalyst composition comprising one or more compound according to any one of claims 1-46.
48. The catalyst composition of claim 47, comprising a compound of formula II.
49. The catalyst composition of claim 47, comprising a compound of formula III.
50. The catalyst composition of claim 47, comprising a compound of formula III and a compound of formula II.
51. The catalyst composition of claim 50, comprising a compound of formula IIIb and a compound of formula IIb.
52. The catalyst composition of claim 47, comprising a compound of formula IIIsyn and a compound of formula IIIanti.
53. The catalyst composition of any one of claims 47-52, further comprising a metal- alkylidene compound of formula V
Figure imgf000088_0001
, wherein Z, M, X, Y, and the R group are according to claim 1.
54. The catalyst composition of claim 53, wherein R is methyl.
55. The catalyst composition of claim 54, wherein compound of formula V is W(NCPh3)(OSiPh3)2(CMe2).
56. A method for converting a tungsten or molybdenum based ^, ^'-dialkyl metallacyclopentane compound into its metal-alkylidene isomer, comprising irradiating the ^, ^’- dialkyl metallacyclopentane compound with light, wherein the ^, ^’-dialkyl groups taken together with the ^, ^’ carbons may optionally form a ring A fused to the metallacyclopentane ring.
57. A method for producing a catalyst compound of formula III or activating a compound of formula II, comprising irradiating the compound of formula II with light.
58. The method of claim 56 or 57, wherein the light comprises or consists of blue light.
59. The method of claim 56 or 57, wherein the light comprises or consists of a wavelength range of about 380-500nm, 390-470nm, or 400-450nm.
60. The method of claim 59, wherein the light comprises or consists of a wavelength of 405, 410, 420, 430, 440, 450, or 460nm.
61. The method of claim 60, wherein the light comprises or consists of a wavelength of 405, or 450nm.
62. The method of any one of claims 57-61, wherein the compound of formula II is irradiated with light without heating.
63. The method of any one of claims 57-61, wherein the compound of formula II is irradiated with light at a temperature of about -40 to -90°C.
64. The method of any one of claims 57-61, wherein the compound of formula II is irradiated with light at room temperature of about 20-25 °C.
65. The method of any one of claims 57-61, wherein the compound of formula II is irradiated with light at a temperature of about 30 to 50°C.
66. The method of any one of claims 57-65, further comprising producing compound of formula II by contacting a compound of Formula I with an alkene compound
Figure imgf000089_0001
, wherein M, Z, X and Y are according to claim 1.
67. The method of claim 66, wherein the alkene compound is a terminal alkene (e.g., 1- heptene).
68. The method of claim 66, wherein the alkene compound is C3-C12, C4-C12, or C5-C12 alkene.
69. The method of claim 66, wherein the alkene compound is C3-C10, C4-C10, or C5-C10 alkene.
70. The method of claim 66, wherein the alkene compound is a terminal alkene having two terminal C=C bonds (e.g., 1,6-heptadiene).
71. The method of any one of claims 66-70, wherein the contacting a compound of Formula I with an alkene compound is conducted in the dark.
72. The method of any one of claims 66-71, wherein the contacting a compound of Formula I with an alkene compound is conducted at a temperature of about 70-110°C or 90-95°C.
73. The method of any one of claims 66-72, wherein the contacting a compound of Formula I with an alkene compound is conducted for about 1 hour to 24 hours.
74. The method of claim 73, further comprising removing volatile material (e.g., applying vacuum).
75. The method of claim 66, comprising a) contacting a compound of formula I with an alkene compound, b) preventing light exposure (prior to, or during the contacting), c) heating (prior to, or during the contacting), d) removing volatile material, and e) dissolving residue in organic solvent (e.g., toluene).
76. The method of claim 75, further comprising repeating the steps a)-e) for one or more times.
77. A method for catalyzing a metathesis reaction, comprising contacting one or more reactant compound(s) with a catalyst compound or composition according to any one of claims 1-55.
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