DE19854869A1 - Process for the preparation of ruthenium complexes - Google Patents

Abstract

The invention relates to a method of producing ruthenium complexes of general formula (I): RuX2(=CH-CH2R)L<1>L<2>, wherein X is an anionic ligand, R is hydrogen or an optionally substituted C1-20 alkyl radical or C6-20 aryl radical, and L<1> and L<2> independently are neutral electron-donor ligands. Said ruthenium complexes are produced by a) reacting RuX3 with a diene in a solvent on the basis of one or several aliphatic secondary alcohols in the presence of a reducing adjuvant, reacting said mixture with L<1> and L<2> in the presence of at least one coordinating weak base and hydrogen and without isolating any intermediates, b) reacting the mixture with compounds of general formula (II): R-C=CH, wherein R has the meaning indicated above, in the presence of a soluble chloride source.

Description

The invention relates to processes for the preparation of ruthenium complexes which for example, can be used as catalysts in metathesis reactions.

The simplest form of olefin metathesis (disproportionation) is one reversible, metal - catalyzed transalkylidation of olefins by breaking and Reforming of carbon-carbon double bonds takes place. In the case of For example, a distinction is made between the metathesis of acyclic olefins Self-metathesis, in which an olefin is mixed into a mixture of two different olefins molar masses (e.g. conversion of propene to ethene and 2- Butene), and the cross or co-metathesis, which is an implementation of two describes different olefins (for example of propene with 1-butene Ethene and 2-pentene). To the other fields of application of olefin metathesis count syntheses of unsaturated polymers by ring opening Metathesis Polymerization (ROMP) of Cyclic Olefins and the Acyclic Diene Metathesis polymerization (ADMET) of α, ω-dienes. Concerning newer applications open the selective ring opening of cyclic olefins with acyclic olefins, as well as ring closure reactions (RCM) with which - preferably from α, ω-dienes - Unsaturated rings of different ring sizes can be produced.

In principle, homogeneous and are suitable as catalysts for metathesis reactions heterogeneous transition metal compounds, especially ruthenium compounds.

Heterogeneous catalysts, for example molybdenum, tungsten or rhenium oxides on inorganic oxidic supports, stand out in reactions of  non-functionalized olefins characterized by high activity and regenerability, However, when using functionalized olefins, such as methyl oleate, Increased activity can often be pretreated with an alkylating agent. Olefins with protic functional groups (such as hydroxyl groups, carboxyl groups or Amino groups) lead to spontaneous deactivation of the heterogeneous contact.

Efforts have been made in recent years, in protic To produce medium and homogeneous catalysts stable in atmospheric oxygen. Special ruthenium alkylidene compounds are of particular interest found. Such complexes and processes for their preparation are known.

WO 93/20111 describes ruthenium and osmium metal carbene complexes for olefin metathesis polymerization. The complexes have the structure RuX ₂ (= CH-CH = CR ₂ ) L ₂ . Triphenylphosphine and substituted triphenylphosphine are used as ligands L. They are produced, for example, by reacting RuCl ₂ (PPh ₃ ) ₃ with suitable disubstituted cyclopropenes as carbene precursors. However, the synthesis of cyclopropene derivatives is multi-stage and of little economic interest.

Similar implementations are described in WO 96/04289. There are also procedures specified for olefin metathesis polymerization.

Use of such catalysts for the peroxide crosslinking of ROMP Polymers is described in WO 97/03096.

WO 97/06185 likewise describes metathesis catalysts which are based on ruthenium metal-carbene complexes. In addition to the process described above, they can also be prepared by reacting RuCl ₂ (PPh ₃ ) ₃ with diazoalkanes. However, handling diazoalkanes poses a security risk, especially when the process is carried out on a technical scale.

In addition, the organometallic starting materials of the formula RuCl ₂ (PPh ₃ ) ₃ used have to be prepared from RuCl ₃ 3 H ₂ O using a large excess of triphenylphosphine. In the catalyst synthesis itself, PPh ₃ ligands are then lost again after ligand exchange. The carbene precursors used require multi-stage syntheses and are not stable indefinitely.

Organometallics 1996, 15, 1960 to 1962 describes a process for the preparation of ruthenium complexes in which polymeric [RuCl ₂ (cyclooctadiene)] _x in i-propanol is reacted with hydrogen in the presence of phosphine and then with 1-alkynes. This eliminates the need for phosphine exchange. An undefined mixture of products is obtained. In addition, long reaction times are required starting from a polymeric starting material. The cyclooctadiene contained in the organometallic starting material does not contribute to the reaction and is lost.

In J. Chem. Soc. Commun. 1997, 1733 to 1734 a synthesis of the methylene complex RuCl ₂ (= CH ₂ ) (PCy ₃ ) _{2 is} described, which starts from dichloromethane and the ruthenium polyhydride RuH ₂ (H ₂ ) ₂ (PCy ₃ ) ₂ . However, the ruthenium-polyhydride complex is difficult to access. Long reaction times are also required.

The known synthetic routes for the production of metathesis catalysts of the RuX ₂ (= CH-CH ₂ R) (PR ' ₃ ) _{2 type} are uneconomical for the reasons mentioned.

The older, not prepublished DE-A198 00 934 describes a process for the preparation of RuX ₂ (= CH-CH ₂ R) L ¹ L ² ruthenium complexes, in which RuX ₃ in an inert solvent in the presence of a reducing agent and Hydrogen and then reacted with alkyne compounds.

The object of the present invention is to provide a process for the preparation of ruthenium-alkylidene complexes of the type RuX ₂ (= CH-CH ₂ R) L ¹ L ² , which can be carried out in a rapid and atomically economical implementation, starting from easily accessible starting materials, without ligand exchange and without Ligand excess leads to the desired products in high yield. In addition, the process should do without complex workup steps, should be able to be carried out under mild reaction conditions and should also be inexpensive.

The object is achieved according to the invention by a process for the preparation of ruthenium complexes of the general formula I.

RuX ₂ (= CH-CH ₂ R) L ¹ L ² (I)

in the
X is an anionic ligand,
R is hydrogen or an optionally substituted C _1-20 alkyl radical or C _6-20 aryl radical, and
L ¹ and L ^{2 are} independently neutral electron donor ligands,
by

• a) Reaction of RuX ₃ with a diene in a solvent based on one or more aliphatic secondary alcohols in the presence or absence of a reducing aid, and then with L ¹ and L ² in the presence of at least one coordinating weak base and of hydrogen and without isolation of intermediates
• b) b) subsequent reaction with compounds of the general formula II
  RC∼CH (II)
  in which R has the meaning given above, in the presence of a soluble chloride source.

It was found that the above ruthenium complexes directly from RuX ₃ , preferably RuCl ₃ .3 (H ₂ O), by simple reaction with dienes and then with ligands L ¹ and L ² , hydrogen and terminal alkynes of the general formula II, preferably in the presence reduction aids can be obtained in very good yields without isolation of intermediates. The ruthenium complexes contain no vinyl substituents on the carbene carbon atom. The raw materials are inexpensive to manufacture and readily available.

First, RuX _{3 is} reacted with the diene and then with the ligands L ¹ and L ² in a solvent based on one or more aliphatic secondary alcohols, preferably in the presence of a reducing aid, at least one coordinating weak base and hydrogen. The solvent is based on one or more aliphatic secondary alcohols. These alcohols preferably have 3 to 10, particularly preferably 3 to 6, carbon atoms. Isopropanol, 2-butanol, cyclohexanol or a mixture thereof are particularly preferred. Isopropanol is particularly preferably used.

The coordinating weak base is a secondary, or preferably a tertiary Amine. An example of a secondary amine is dicyclohexylamine. Especially Preferred are tertiary aliphatic amines, especially trialkylamines, in which the Alkyl radicals have 1 to 12, preferably 2 to 6, carbon atoms. Particularly preferred triethylamine is used. The coordinating weak base, especially that Triethylamine, is preferably obtained in at least a stoichiometric amount used on RuX. The reaction mixture is preferably added before the addition of the ligand L pretreated with the coordinating weak base.  

Before the addition of the ligand L, the reaction mixture is reacted with a diene, preferably C ₄ to C ₁₀ diene, in particular isoprene, preferably in the presence of a reducing aid, in particular an alkali metal or alkaline earth metal carbonate. Sodium carbonate and / or calcium carbonate are particularly preferably used as alkali or alkaline earth carbonate. The molar ratio of diene to RuX _{3 is} preferably at least 5: 1 and the molar ratio of alkali and / or alkaline earth carbonate to RuX _{3 is} 0.1 to 1, particularly preferably about 0.5.

The reduction with hydrogen takes place in the presence of a coordinating one weak base, preferably a secondary or tertiary amine. Especially Triethylamine is preferably used.

The reaction mixture is reacted with a 1-alkyne in the presence a soluble chloride source, especially an alkaline earth metal chloride. Especially magnesium chloride is preferably used.

The temperature in this reaction step (a) is preferably 0 to 100 ° C., particularly preferably 20 to 80 ° C., in particular 40 to 60 ° C. The pressure is preferably 0.1 to 100 bar, particularly preferably 0.5 to 5 bar, in particular 0.8 to 1.5 bar. The reaction takes place for a period of preferably 10 minutes to 100 hours, particularly preferably one hour to 10 hours. The molar ratio of ligands L ¹ and L ^{2 taken} together to the ruthenium salt used is preferably 2 to 20: 1, particularly preferably 2 to 5: 1. After the reaction in step (a), the reaction mixture is preferably at a temperature in the range from -80 to 100 ° C, particularly preferably -40 to 50 ° C, in particular -30 to 20 ° C with a 1-alkyne. The molar ratio of the ruthenium salt to 1-alkyne originally used is preferably 1: 1 to 1:10. The reaction is preferably carried out at a pressure of 0.1 to 10 bar, particularly preferably 0.8 to 1.5 bar, in particular 1 up to 1.4 bar for a period of preferably 30 seconds to 10 hours, particularly preferably one minute to one hour.

To prepare the complexes of the general formula I, no isolation of the Intermediate from step (a) required, but possible.

The reaction mixture obtained is preferably worked up by Filter off the precipitated solid, wash and dry.

In the ruthenium complexes of the general formula I, X is a monodentate anionic ligand, for example halogen, pseudohalogen, carboxylate, diketonate. X particularly preferably denotes halogen, in particular bromine or chlorine, especially chlorine. RuCl ₃ .3H ₂ O is particularly preferably used in the reaction.

L ¹ and L ² are neutral electron donor ligands. Examples include amines, phosphines, arsanes and stibans, preferably phosphines. L1 and L2 are particularly preferably selected from phosphines of the general formula III

PR ¹ R ² R ³ (III)

in which R ¹ and R ^{2 are} independently phenyl radicals or organic sterically hindering radicals and R ^{3 is} hydrogen, an optionally substituted C _1-20 alkyl radical or C _6-20 aryl radical or as R ^{1 is} defined. "Sterically hindering residue" is understood to mean those residues which have a spatially demanding structure. Examples of such radicals are i-propyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl or menthyl. A cyclohexyl radical is preferably used as the sterically hindering radical. All three radicals R ¹ , R ² and R ³ are particularly preferably sterically hindering radicals or phenyl radicals, in particular cyclohexyl radicals. The radicals R ¹ , R ² and R ³ can each carry suitable substituents. Examples of such substituents are C _1-6 alkyl, preferably C _1-3 alkyl, C _1-3 fluoroalkyl, halogen atoms, nitro groups, amino groups, ester and acid functions, -OH, C _1-6 alkoxy groups or sulfonate groups. The radicals are preferably not substituted. L ¹ and L ² are preferably used in a molar ratio of 1.5 to 4, particularly preferably about 2, based on RuX ₃ .

The radical R is hydrogen or an optionally substituted C _1-20 , preferably C _1-6 alkyl radical or C _6-20 , preferably C _6-8 aryl radical. What has been said above applies to the substituents. Particularly preferred as the ruthenium complex of the general formula I are the complexes RuCl ₂ (= CH-CH ₃ ) (PCy ₃ ) ₂ and RuCl ₂ (= CH-CH ₂ -Ph) (PCy ₃ ) ₂ where Cy is a cyclohexyl radical and Ph is a phenyl radical mean.

In a preferred embodiment, RuCl ₃ xH ₂ O with Na ₂ CO ₃ or CaCO ₃ in isopropanol, 2-butanol or cyclohexanol is introduced in a one-pot reaction (under an inert gas atmosphere) and heated after the addition of isoprene. After excess isoprene has been removed in vacuo, triethylamine and stoichiometric amounts of phosphane, in a preferred embodiment two equivalents of tricyclohexylphosphine, are added to the reaction mixture. In a hydrogen atmosphere of 0.1 bar to 100 bar, preferably 0.5 to 5 bar, particularly preferably 0.8 to 1.5 bar, the mixture is then stirred for 10 minutes to 100 hours at temperatures from 0 ° C. to 100 ° C. and then MgCl ₂ x6H ₂ O added. The reaction mixture thus obtained is then at a temperature of -80 ° C to 100 ° C, preferably at -40 ° C and 50 ° C in a molar ratio of 1: 1 to 1:10, based on the ruthenium chloride used, with a 1-alkyne the composition HC∼CR at pressures of 0.1 to 10 bar, preferably at 0.8 to 1.5 bar, continuously implemented over a period of 30 to 180 min. The solid which precipitates from the solution approximately quantitatively is the desired alkylidene complex which, after drying, can be used directly as a highly active metathesis catalyst for all of the metathesis reactions described in the introduction.

As a rule, the entire reaction and workup sequence is complete after 2 to 100 h, preferably after 3 h to 8 h, and gives metathesis catalysts of the RuCl ₂ (= CHCH ₂ R) (PR ' ₃ ) ₂ (R = H, alkyl, aryl) in yields of at least 60 to 98% based on RuCl ₃ and the phosphine used.

Glass or steel containers are generally suitable as reactors, which should be pressure stable if necessary.

The invention is illustrated by the example.

example Synthesis of the ethylidene complex RuCl ₂ (= CHMe) (PCy ₃ ) ₂

1.09 g (3.95 mmol) RuCl ₃ .3H ₂ O and 198 mg CaCO ₃ (1.98 mmol) are mixed with 4 ml isoprene (40.0 mmol) under protective gas in 150 ml isopropanol, and the reaction mixture is Heated to 85 ° C in a closed flask for 1 to 2 h, a color change from red to brown-black to orange-red being observed. The heating is removed, the volume of the solution is reduced by about 20 to 30 ml and the mixture is stirred for 5 min after the addition of 2 ml of triethylamine (14.4 mmol). 2.24 g of tricyclohexylphosphine (7.99 mmol) are then added. After stirring for 10 minutes, the protective gas is now replaced by hydrogen at a pressure of 0.6 to 0.8 bar and the reaction solution is heated to 65 ° C. for 45 minutes, an orange-yellow suspension having formed after only 15 minutes. After the suspension has cooled to room temperature, hydrogen is replaced by protective gas, and after adding 1.60 g (7.87 mmol) of MgCl ₂ x6H ₂ O, 220 ml of acetylene (approx. 4.6 mmol) are continuously added over a period of 90 min. added. After the addition is complete, the suspension is stirred for a further 10 min. A vacuum is briefly applied to remove residual amounts of acetylene. The violet solid which has precipitated out of the solution is filtered off, washed with water and methanol and dried in vacuo.
Yield: 2.85 g (93%)

Claims (11)

1. Process for the preparation of ruthenium complexes of the general formula I
RuX ₂ (= CH-CH ₂ R) L ¹ L ² (I)
in the
X is an anionic ligand,
R is hydrogen or an optionally substituted C _1-20 alkyl radical or C _6-20 aryl radical, and
L ¹ and L ^{2 are} independently neutral electron donor ligands,
by

• a) Reaction of RuX ₃ with a diene in a solvent based on one or more aliphatic secondary alcohols in the presence or absence of a reducing aid, and then with L ¹ and L ² in the presence of at least one coordinating weak base and of hydrogen and without isolation of intermediates
• b) subsequent reaction with compounds of the general formula II
  
  RC∼CH (II)
  in which R has the meaning given above, in the presence of a soluble chloride source.

2. The method according to claim 1, characterized in that the reaction mixture before the addition of the ligands L ¹ and L ² with a diene in a molar ratio of at least 5: 1, based on RuX ₃ , is added. 3. The method according to claim 1 or 2, characterized in that L ¹ and L ^{2 are} selected from phosphines of the general formula III
PR ¹ R ² R ³ (III)
in which R ¹ and R ^{2 are} independently phenyl radicals or organic sterically hindering radicals and R ^{3 is} hydrogen, an optionally substituted C _1-12 alkyl radical or C _6-20 aryl radical or as defined for R ¹ . 4. The method according to claim 3, characterized in that R ¹ and R ^{2 are} selected from i-propyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl or menthyl. 5. The method according to any one of claims 1 to 4, characterized in that X Halogen means. 6. The method according to any one of claims 1 to 5, characterized in that the reaction of RuX _{3 is carried out} with a diene in the presence of Na ₂ CO ₃ and / or CaCO ₃ , the molar ratio of Na ₂ CO ₃ and / or CaCO ₃ for RuX _{3 is} 0.1 to 1. 7. The method according to any one of claims 1 to 6, characterized in that the Reaction with hydrogen in the presence of a secondary and / or tertiary Amine is performed as a coordinating weak base. 8. The method according to any one of claims 1 to 7, characterized in that the Reaction with 1-alkynes carried out in the presence of an alkaline earth chloride becomes. 9. The method according to any one of claims 1 to 8, characterized in that the Implementation in step (a) at a pressure in the range from 0.1 to 100 bar and carried out in step (b) at a pressure in the range from 0.1 to 10 bar becomes. 10. The method according to any one of claims 1 to 9, characterized in that the Reaction in step (a) at a temperature in the range from 0 to 100 ° C and in step (b) at a temperature in the range of -80 to 100 ° C is carried out. 11. The method according to any one of claims 1 to 10, characterized in that the solvent is selected from isopropanol, 2-butanol, cyclohexanol and mixtures thereof.