Alkyl halides with transition metal reagents

As indicated in Table II, the complexes examined thus far have all contained coordinatively unsaturated dH or d10 metal ions, as has most commonly been the case in oxidative addition reactions of alkyl halides with transition metal substrates. Almost all of the products of these reactions are immediately recognizable as having arisen from an oxidative addition reaction, but in some instances the species isolated, e.g., CF3Au(P3) (59), (CF3)2Pt(COD) (54), and CF3Pt(PEt3)2I (55), were found to be in the same oxidation state as the reagents that had been originally employed. 

Zapf, A. Coupling of Aryl and Alkyl Halides With Organoboron Reagents (Suzuki Reaction). In Transition Metals for Organic Synthesis (2nd edn), Beller, M. Bolm, C. eds., 2004, 1, 211-229. Wiley-VCH Weinheim, Germany. (Review). 

Table 7.1 Transition-metal catalysed cross-coupling reaction of alkyl halides with grignard reagents in the presence of 1,3-butadiene.

The role of aluminoxane in polymerization with transition metal complexes has not been completely clarified. It certainly serves as the alkylating reagent of the transition metal halides to produce metal dialkyls. Methylaluminoxane, having Lewis acidity, can abstract one of the two alkyl groups at the metal center and creates a cationic metal alkyl species with a readily accessible coordination site for the incoming olefin molecules. As described previously, a cationic monoalkyl complex having a vacant coordination site for the monomer is suitable in accepting the monomer and initiate the polymerization. Abstraction of one of the methyl... 

Reactions.—New systems for the reduction of alkyl halides to alkanes include mixtures of lithium aluminium hydride with transition-metal chlorides (such as Ni or Co" chlorides) and some complex metal hydrides of copper, especially the THF-soluble Li4CuHs. Details of the application of sodium cyanoborohydride to the reduction of halides (and sulphonate esters) in dipolar aprotic solvents have been published. Virtually all other functional groups are inert to this convenient, mild, and efficient system, which has been used to develop a one-pot deoxygenation of primary alcohols (Scheme 39) via the iodides. The alternative cyanoborohydride reagents (55) and the polymeric (56) are also discussed. ... 

Analogously, zinc reagents react with halides of various elements. They are particularly useful for the alkylation of halides of transition metals such as NbCls and TaCls that are too easily reducible by alkali metal alkyl reagents. Up to three halides can be substituted by alkyl groups R using ZnRj in these transition-metal halides. 

Among others, alkyls of Be, Cd, Hg, Al, Sn, Pb, Co, Pt, and Au have been prepared by treatment of Grignard reagents with the appropriate halide. The reaction has been used to prepare alkyls of almost all non-transition metals and even of some transition metals. Alkyls of metalloids and of nonmetals, including Si,... 

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