CA1083591A

CA1083591A - Organomagnesium complexes

Info

Publication number: CA1083591A
Application number: CA250,310A
Authority: CA
Inventors: Dennis B. Malpass
Original assignee: Texas Alkyls Inc
Current assignee: Texas Alkyls Inc
Priority date: 1975-04-23
Filing date: 1976-04-14
Publication date: 1980-08-12
Also published as: DE2615351A1; GB1526455A; FR2308632B1; NL7604349A; ES447273A1; FR2308632A1; BE841022A; JPS51128921A; DE2615351C2

Abstract

Abstract of the Disclosure Organomagnesium complexes, which have the formula:
(R'2Mg)m ? (RM)n wherein RM is an organozinc or organoboron com-pound, R' is a primary alkyl or aryl group, and having an m:n ratio of about 1 or greater, are disclosed. These complexes are prepared by re-acting magnesium with an organohalide selected from primary alkyl halides or aryl halides in the presence of a hydrocarbon solvent and subsequently adding an organozinc or organoboron compound. Al-ternately, the organozinc or organoboron compound can be generated in situ by adding a zinc or boron salt which is alkylated by the magnesium alkyl.
The organozinc and organoboron compounds function as solubilizing agents for organomagnesium com-pounds which are normally only slightly soluble or insoluble in hydrocarbon media. These com-plexes are characterized by very low halide content, lack of ether contamination, magnesium to metal ratios of from about 1:1 to about 20:1, and hydro-carbon solubility. Even higher ratios are conceivably obtainable. The complexes are useful as co-catalysts in combination with conventional Zeigler catalysts for polymerizing olefins, diolefins and olefin oxides, and as a source of ether-free diorganomagnesium compounds.

Description

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Back~round of the Invention Dialkylmagnesium compounds are well known in the art.
However, the production of soluble dialkylmagnesium compounds, free of sol~ation and chloride, by the direct reaction of mag-nesium with a halide, has here~o~ore been unsuccessful except in very specific systems. Thus, Glaze and Selman, Journal of Organometallic Chemistry, volume 5, page 477 (1967), produced soluble di-n-amylmagnesium by reaction of powdered magnesium metal with n-amyl chloride and then re~luxing the product with benzene. W. N. Smith, Jr. (J. Organometal Chem., 64, 25 (1974) investigated the direct reaction of alkyl halides, especially long chain n-alkyl halides, with magnesium in the absence of organic bases. The resultant products, however, often showed ` limited solubility and/or high residual halogen content. These methods, however, are imapplicable to other dialkylmagnesium compounds, particularly n-butyl or lower primary alkyl-magnesium compounds, due to their high degree of insolubility. In fact, Kamienski and Eastham, in the Journal of Organic Chemistry, volume 34, page 1116 (1968), found it impossibLe to prepare di-sec-butylmagnesium by the Glaze and Selman method. They were able to prepare di-sec-butyl chloride in the presence of an ether catalys, but the resultant product contained soluble chloride.
These same authors were able to prepare hydrocarbon solutions of di-sec-butylmagnesium by an exchange process employing an acti-vated form of magnesium chloride and sec-butyllithium in hydro~
carbon media. However, this synthetic technique is not applicable to most magnesium alkyls, since these compounds are generally insoluble in hydrocarbon.

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~33591 Various organoaluminum-organomagneslum complexes have been prepared by reaction of a trialkylaluminum compound with a desolvated (ether-free) Grignard reagent, by electrolysis of mixtures of alkali metal tetraalkylaluminates using a magnesium S anode, and by the reaction of dialkylmagnesium compounds, pre-pared via the mercury-magnesium exchange method, with trialkyl aluminum compounds. The complexes prepared by these processes have low Mg/Al ratios, in the range of 0.5 to 1.0 depending upon the stoichiometry of starting materials.
The electrolysis method requires the use of mixed R4AlM compounds (M=alkali metal) in a mol~en state and the pre-ferred temperature range is 100-125C. See for example, U.S.
Patent No. ~,028,319. This temperature range precludes the preparation of complexes which may be easily pyrolyzed, for example, when RGisobùtyl. Furthermore? complexes with Mg/Al ratios greater than 0.5 are not produced by this procedure.
The complexes Me8A12Mg and Me5AlMg prepared by the procedure of Stucky and Atwood, Journal_of _he American Chemical Society, volume 91, page 2538 (1969), had significantly different properties than supposedly the same compounds prepared earlier by Ziegler, Annalen d~r Chemie, volume 605, page 93 (1957).
The discrepancy may be due to incomplete removal of ether in the Grignard reagent used by Ziegler, since dialkylmagnesium and Grignard reagents are known to be difficult to free of com-plexed ethers.
Recently, hydrocarbon soluble magnesium alkylaluminum ` alkyl complexes were prepared by interaction of organo-aluminum compounds with the reaction product of magnesium with alkyl halides (U.S. 3,737,393).

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:`' : :'`, ' ~()83S91 It is an object o the present invention to prepare hydrocarbon soluble organom~gnesium complexes, including those - complexes containing the normally insoluble lower dialkylmag-nesium compounds suitable for use as co-ca~alysts for the polymerization of olefins, diolefins, or olefin oxides.
It is another object of the present invention to pre-pare organomagnesium complexes wherein the Mg/M ra~io is about 1 or greater. Other objects of the present invention will be-come apparent from the description contained below.

Detailed Description of the Disclosure The present invention relates to organomagnesium - complexes of the formula:
(R 2Mg)m (RM)n wherein RM is an organozinc or organoboron compound~ R is a primary, secondary, or tertiary alkyl group, R' is a primary Cl to C10 alkyl or phenyl group, or mixture thereof, and m and n are numbers such that the ratio o m/n is a~out 1 or greater.
In the preferred embodiment of the present invention, R is Cl-C~
alkyl, which is either straight or branch chained, R' is methyl, ethyl, n-propyl, n-butyl, or n-amyl, and m/n is between 1 and 10.
Particùlarly preferred in the present invention are those com-plexes wherein R' is a Cl-C4 primary alkyl group.
These complexes are prepared by reacting magnesium metal with a primary alkyl halide or aryl halide in the presence of a hydrocarbon solvent and, directly thereafter, adding an organoæinc or organoboron compound selected from ~he group con-sisting of dialkylzinc, alkylzinc halide, trialkylboron, :~ dialkylboron halide or alkylboron dihalides.

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Alternately, the org~nozinc or organoboron compound may be gen-erated in situ by alkylation of a zinc or boron salt by the organomagneslum as follows:
'~ R2Mg ~ ZnX2 ~ R2Zn ~ MgX
3R2Mg ~ 2~X3 ) 2R3B -t 3MgX2 ~
where X is a halogen, alkoxyl or carboxyl group. The resul-tant R2Zn and R3B then serves as a solubilizing agent for excess R2Mg.
After filtration of the reaction mixture, the resul-ting solution contains the organomagnesium complexes of the present invention and can then be diluted or concen~rated as desired. The complexes can be isolated by distilling off all of the solvent to yield the viscous liquid or solid complex.
However, it is preferred to handle these complexes in solution.
15 The organomagnesium moiety in the complexes of the present invention is generally derived from bis primary dialkyl- or diarylmagnesium compounds, obtained via the di-rect reaction of magnesium with a hydrocarbon halide in a hydrocarbon solvent. Although the present invention is not limited by the particular theory of the reac~ion mechanism, it is thought to proceed through a Grignard-type intermediate (RMgX)n which, in the absence of a solvating species ? disproportionates via the Schlenk equilibrium to dialkylmagnesium and magnesium halide as follows:

2~iR'X -t 2~g ~ (R'MgX)2m~ mR 2Mg ~ ~gx2 The extent of the dispropor~ionation is dependen~ upon the nature of the solvent, the nature o ~he alkyl or ar~JL group, and the particular halide involved. In the present disclosure, .

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this equilibrium is shifted eompletely to the right ~y the - interaction of the organozinc or organoboron compound with ~he diorganomagnesium reagent to form a hydroearbon soluble complex.
Illustrative o these organomagnesium compounds are the follow-ing: dimethylmagnesium, diethylmagnesium, di n-propylmagnesium, di-n~butylmagnesium, di-n-amylmagnesium, di-n-hexylmagnesium, diphenylmagnesium, and the like. The preferred compounds are dimethylmagnesium, diethylmagnesium, di-n-butylmagnesium and di n-amylmagnesium. Particularly preferred are the primary alkyl -~ 10 magnesium compounds wherein the alkyl group is n-butyl and n-amyl.
The organoæinc or organoboron compounds are generally derived from dialkylzinc, alkylzinc halides, trialkylborons, dialkylboron halides, and alkyiboron dihalides. Illustrative of the organozinc compounds are the following: dimethylzinc, diethylzinc, di-n-propyIzinc, diisopropylzinc, di-n-butylzinc, di-sec-butylzinc, di-tert-butylzinc, methylzinc halides, ethylzinc halides, propylzinc halides, and butylæinc halides.
Preferred organozinc compounds for the complexes of the present invention are those wherein the alkyl group is from 1 to 4 car-bon atoms or mixtures thereof. The alkyl group of these preferred moieties can be primary, secondary, or tertiary.
~ Illustrative of the organoboron compounds are the fol-i lowing: trimethylboron, triethylboron, triisopropylboron, tri-n-propylboron, tri-n-butylboron, tri-sec-butylboron, tri-tert-butylboron, dimethylboron halides, diethylboron halides, di-propylboron halides, dibutylboron halides, methylboron dihalides, ethylboron dihalides, propylboron dihalides, butylboron dihalides, and the like.

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Illustrative of zinc salts which can be used to generate organozinc compounds in situ are the following: zinc chloride, zinc bromide, zinc iodide, zinc methoxide, zinc ethoxide, zinc isopropoxide, zinc acetate, and the like.
Illustrative of boron salts are the following: boron trifluoride, boron trichloride, boron tribromide, boron triiodide, trimethylborate, triethylborate, triisopropyl borate and the like.
With regard to the reaction of the organomagnesium with RM, the reaction appears to proceed according to the following overall equation:
2mR'X ~ 2mMg + nRM -~ (R 2Mg)rn (RM)n ~ mMg~2 wherein RM is an organozinc or organoboron compound, R' is an alkyl or phenyl group or mix~ure thereof, X is a halide, and m and n are numbers such that the ratio of m/n is about 1 or greater.
~s stated previously, the complexes of the present invention are prepared by initially reacting magnesium with a halide of the formula:
, R'X
wherein R' is as defined above and X is a halogen such as chlorine or bromine, and subsequently adding an organozinc or organoboron compound directly to the reaction product.
Although magnesium turnings or shavings of commercial grade that have been further activated by milling or any other of the kno~m methods for activating magnesium can be used in ` the processes herein described for the preparation of diorgano-magnesium complexes, it is preferable to use magnesium powder.

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The magnesium and the organic halide are normally reacted in a molar ratio of 1.2 to 1.0, i.e., a 20% molar excess of magnesium. It is understood, however, that the ratio of reactangs can be varied in the range from about 1 to 2 moles of magnesium per mole of halide, and preferably in the range ~rom about 1.1 to 1.3, i.e., a 10-30% excess magnesium. This excess magnesium is desirable to minimize coupling.
The reaction of the organohalide with magnesi~m can be conducted in the absence of a solvent and the product R'2Mg sub-sequently extracted from the solids with the organozinc ororganoboron compound in a suitable solvent. The organozinc or organoboron compounds function as a solubilizing agent for the organomagnesium compounds, which are normally insoluble. However, it is preferable that the initial reaction of the magnesium with the halide be conducted in a hydrocarbon solvent followed by the addition of the organozinc or organoboron compound.
The term hydrocarbon solvent as used herein is meant to designate both aliphatic and aromatic hydrocarbons. Illustra-tive of the hydrocarbons which can be used in the present invention are the following: isopentane, n-hexane, n-heptane, n-octane, cyclohexane, methylcyclohexane, benzene, and toluene. Particu-larly preferred solvents are those aliphatic and aromatic hydro-carbons which boil between 69 and 110C. The hydrocarbon sol~ent is normally employed in amounts from about 10 to 20 times the weight of magnesium charged.
The amount of organozinc or organoboron compound which is added to produce the complexes o~ the present invention is normally less than one mole per mole o~ solubillzable organomag-nesium and is preferably in the molar range of from ab~ut 1:1 to .
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about 1:20 and above, but most preferably 1:1 ~o about L:10, based on a 70% yield o R'2Mg. Recoveries of about 60-80% of the theoretical amount of dialkylmagnesium have been achieved.
The remaining portion of the original starting materials is presumably lost to thermal decomposition and coupling.
It will be apparent to one skilled in the art that by employing the organomagnesium compound in amounts greater than 1:1 with the magnesium, organomagnesium complexes in which the Mg/M ratio is less than one can also be prepared.
Thus, in its broadest aspect, the process embodiment o~ the present invention encompasses the preparation o~ soluble ~; organoaluminum-organomagnesium complexes of the formula:
(R'2Mg) (RM)n wherein RM is an organozinc or organoboron compound, and n and m are numbers such that the ratio m/n i5 from about 0.1 to about 20 and above, and preferably from about 0.25 to about 10.
The initial reaction of the magnesium metal can be carried out at temperatures between 20C and 200C with the preferable range being between about 60C and 100C. The sol-ubilization s~ep proceeds well at room temperature and is normallycompleted in 2-3 hours. However, to facilitate solubilization, it is permissible to heat the reactant mixture during the sol-ubilization step. The upper temperature limit for this step is dependent upon the particular solubilizing compound used. Thus, if di-sec-butylzinc is used, the upper limit will be just below the decomposition temperature of di-sec-butylzinc.
It is essential to carry out the reactions of the present invention in the absence of oxygen. Thus, the manipulat~ve steps of the process are normally carried ou~ under an atmospheric : ' .

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1~8355~1 pressure of an inert gas such as nitrogen or argon. The pressure under which the present invention is conducted is not critical and elevated pressures of several atmospheres can be employed.
It has been found desirable to vigorously stir the reactant mix-ture during both the initial reaction of the magnesium and halideand the subsequent addition of the organozinc or organoboron com-pound. The reactant mixture obtained after the addition of the organozinc or organoboron compound is normally ~iltered and the solid washed with several portions of the hydrocarbon solvent used. The resultant wash solution can then be added to the fil-:~ trate.
It is apparent to one skilled in the art that the com-plexes of the present invent~on are a mixture of complexes having different values for m and n and that the m~ value as used herein is an average value for these num~ers. It is not necessary, or even desirable, to isolate individual complexes, however, since the mixtures work just as well as the individual complexes.
Furthermore, it is recognized that a certain degree of alkyl group transfer occurs between the zinc or boron and magnesium atoms of the complex. Thus, the formulae given for the complexes of the present invention are empirical rather than exact. --The complexes of the present invention are characteriæed by a high Mg/M ratio. They are further characterized by their freedom from undesirable contamination by halides. Furthermore, since the method of forming the complexes o~ the present inven~ion does not require the use of an ether catalyst, the final product is completely ether-free.
Those compounds of the present invention whlch have ~; sufficiently high Mg/M ratios (m/n of 4 or greater) can be useful .
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in situations where diorganomagnesium reagents are desired, i e., the complexes can be used to stimulate the "pure" organomagnesium reagent in reactivity, since they can contain 80 mole percent or greater R'2Mg. In this regard, the complexes of the present in-S vention have the substantial advantage in that they are highlysoluble in hydrocarbon solvents, whereas the pure diorganomag-nesium reagents are, in general, insoluble. Since these complexes are completely free of ether contamination, they can be used as Ziegler-type catalysts without catalyst poisoning which may.result - 10 from ~he ether contamination. Organomagnesium compounds are ef-fective catalysts for the polymerization of ethylene or propylene in the presence of titanium tetrachloride and, for the polymeriza-tion of 1,3-butadiene or 2-methyl~1,3-butadiene in the presence ; of titanium tetraiodide.
The present invention will be further illustrated by the following examples.

To a 300 milliliter three-neck flask equipped with a ;` magnetic stirrer, reflux condenser, and additlon funnel were 20 added 5.84 grams (0.24 gram-atom) of magnesium powder 1.7 g n-butyl chloride and a few crystals o iodine. All equipment was previously flushed while hot with dry nitrogen and all reactions and manipulations carried out under a nitrogen blanket. The mix-ture was heated to ca 70C and reaction initiated. Then benzene 25 (80 ml) was charged to reaction mixture and a solution consisting of 16.8 g n-butyl chloride in 26.6 g benzene was charged to the addition funnel. The mixture was heated to re1ux and the BuCl-benzene added over a 1.5 hour period. During this period the reaction mixture assumed a muddy consistency. The mixture was .

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. , refluxed about 1/2 hour after the addi~ion o the n-butyl chloride solution was complete. A weight o~ 3.1 gram8 (O.OZ5 mole) of diethylzinc was added to the mixture. After 3 hours o,- stirring at 82-84C the mixture was filtered and the solids washed with several portions of benzene which were then added to the filtrate.
Analysis of the filtrate (204.4 g) showed it to contain 0.96% Mg (or a 5.5% solution of n-Bu2Mg) and 0.62% (or 1.2% solution of Et2Zn) and nil chloride. The Mg/Zn ratio in the complex was 4.19 and the amolmt of di-n-butylmagnesium solubilized was 81%.

The same apparatus and procedure as in Example 1 were employed except the reactants were 27.8 grams (0.20 mole) of n-butyl bromide and 2.6 grams (0.21 mole) o diethylzinc. Analy-sis of the reaction supernatant showed a Mg/Zn ratio of 4.70 and the amount of di-n-butylmagnesium solubilized as complex was estimated to be 75%.

The same apparatus and procedure as above were employed except that 18.2 grams (0.20 mole) of n-butyl chloride and 2.7 grams (0.028 mole) of trie~hylboron were used as reactants. The amount of di-n-butylmagnesium solubilized was 65% of theory.

To a three liter ~our-neck flask equipped with a mag-netic stirrerg reflux condenser, and addition funnel were added 20.2 grams (0.83 gram-atom) o magnesium powder and 5.7 g n-butyl chloride. The mixture was heated to ca 70C and reaction initiat-~ ed. Then, hexane (900 ml) was charged to the reaction mixture ``~ and 58.7 g of n-butyl chloride was charged to the addition unnel.
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The mixture was heated to reflu~ a~d ~he BuCl added over a one hour period. During this period the reaction mixture assumed a muddy consistency The mixture was refluxed abou~ two hours after the addition of the n-butyl chloride was complete. The reaction mixture was cooled by adding 809 mls of hexane, then a weight of 5.6 grams (0.045 mole) of diethylzinc was added to the mixture. After 2 hours of s~irring at 66-69C the mixture was filtered. The filtrate was concentrated by distillation of about 1/2 of the hexane under reduced pressure. Analysis of the filtrate (655.0 g) showed it to contain 1.04% Mg (or a 5.9% sol-ution of n-Bu2Mg) and 0.38% Zn (or 0.72% solution of ~t2Zn). The Mg/Zn ratio in the co~aplex was 7.23 and the amount of di-n-butyl-magnesium solubilized was 80%.

To a five liter four-neck flask equipped with a mag-netic stirrer, reflux condenser, and addition funnel were added 55.0 grams (2.26 gram-atom) of magnesium powder, 9.0 g n-butyl chloride and a few crystals of iodine. The mixture was heated to ca 50C and reaction initiated. Then hexane (2600 ml) was `; 20 charged to the reaction mixture and 173.9 g of n-butyl chloride was charged to the addition funnel. The mixture was heated to reflux and the BuCl added over a 1.5 hour period. The mixture was " refluxed about 1/2 hour after the addition of the n-butyl chloride was complete. A weight of 14 8 grams (0.120 mole) of diethylzinc was added to the mixture. After 2 hours of stirring at 50-70C
the mixture was filtered. Analysis of the filtrate (1452.6 g) ; showed it to contain 1.12% Mg (or a 6.4% solution o~ n-Bu2Mg) and 0.40% Zn (or 0.76% solution of Et2Zn). The Mg/Zn ratio in the com-plex was 7.40 and the amount of di-n-butylmagnesium solubilized was 67%
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~ ~ 3 To a three liter four-neck ~lask equipped with a mag-netic stirrer, reflux condenser, and addition ~unnel were added 21.6 grams (0.89 gram-atom) of magnesium powder and 5.3 g n-butyl chloride. The mixture was heated to ca 70C and reac~ion initia-ted. Then hexane (1250 ml) was charged to the reaction mixture and 59.9 g of n-butyl chloride was charged to the addition un-nel. The mixture was heated ~o reflux and the BuCl added over a 40 minute period. The mixture was refluxed about 2-1/2 hours after the addition of the n-butyl chloride was complete. The ; reaction mixture was cooled by adding 155 mls of hexane, then a weight of 4.7 grams (0.048 mole) of triethylboron was added to the mixture, After 1-1/2 hours of stirring at 66-69C the mix-" ture was filtered. The filtrate was concentrated by distillation of about 1/2 of the hexane under reduced pressure. Analysis of the fil~rate (619.8 g) showed to contain 1.00% Mg (or a 5.7%
solution of n~Bu2Mg). The Mg/B ratio in the complex was esti-mated to be 6.6 and the a~ount of di-n-butylmagnesium solubilized was 72%.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An organomagnesium complex having the formula (R'2Mg)m ? (RM)n wherein RM is an organozinc or organoboron compound selected from the group consisting of dialkylzincs, alkylzinc dihalides, trialkylborons, dialkylboron halides and alkyl-boron dihalides or mixtures thereof, the alkyl portion of which R represents a primary, secondary or tertiary alkyl group, R' is selected from the group consisting of primary alkyl containing from 1 to 10 carbon atoms, and phenyl and mixtures thereof, and m and n are numbers such that the ratio of m/n is from 1 to 20.

2. The complex of Claim 1 wherein the ratio of m/n is from about 1 to about 10.

3. The complex of Claim 1 wherein R' is selected from the group consisting of methyl, ethyl, n-propyl, n-butyl, and n-amyl.

4. The complex of Claim 1 where R is selected from C1-C4 alkyl.

5. A process for the preparation of hydrocarbon soluble complexes of the formula:

(R'2Mg)m ? (RM)n wherein RM is an organozinc or organoboron compound selected from the group consisting of dialkylzincs, alkylzinc dihalides trialkylborons, dialkylboron halides and alkylboron dihalides, or mixtures thereof, the alkyl portion of which R represents a primary, secondary or tertiary alkyl group, R' is selected from the group consisting of a primary alkyl containing from 1 to 10 carbon atoms, and phenyl and mixtures thereof, and m and n are numbers such that the ratio of m/n is from about 0.1 to about 20 comprising:

(a) reacting powdered magnesium with an organic halide of the formula R'X wherein R' is as defined above and X is a halogen selected from the group consisting of chlorine and bromine at a temperature in the range of from about 30°C
to about 200°C, said magnesium being present in an amount from about 1 to about 2 moles per mole of organic halide; and (b) adding an organozinc or organoboron compound in less than a 1:1 molar ratio with the magnesium to the reaction mixture of step (a) whereby said complex is formed.

6. The process of Claim 5 wherein the hydrocarbon in which the complex is soluble is selected from the group consisting of cyclohexane, n-hexane, n-heptane, and benzene.

7. The process of Claim 5 wherein step (a) is conducted in the presence of a hydrocarbon solvent.

8. The process of Claim 5 wherein step (b) is conducted at a temperature of from about 60°C to about 100°C.

9. The process of Claim 7 wherein said hydro-carbon solvent is selected from the group consisting of isopentane, cyclohexane, n-hexane, methylcyclohexane, n-heptane, and benzene.

10. The process of Claim 5 wherein said organic halide is selected from the group consisting of methyl chloride, ethyl chloride, n-propyl chloride, n-butyl chloride, and n-amyl chloride.

11. The process of Claim 9 where R is selected from C1-C4 alkyl groups.

12. The process of Claim 5 wherein step (b) is conducted in the presence of a hydrocarbon solvent.

13. The process of Claim 5 wherein said organoboron compound is a trialkylboron, or alkylboron halide compound or mixtures thereof.

14. The process of Claim 5 wherein the organozinc or organoboron compound is generated in situ by charging zinc or boron salt.