Preparation of Organotransition Metal Complexes

The transmetalation causes partial or total replacement of halogeno ligands in the starting transition metal complexes with organic ligands. 

Tetraalkylaurate(lll) complexes were prepared by alkylation of neutral alkyl-gold(lll) complexes by alkyllithium (Eq. 5.9) [32-34]. 

An anionic pentamethylplatinate(IV) complex, LilPtMesCPPhs)], and homolep-tic hexamethylplatinate(IV), Li2[PtMe6], were prepared analogously by stepwise methylation of the neutral methylplatinum complexes [35,36], Eq. 5.10 shows the preparation of the hexamethylrhodate(III) complex, Li3[RhMe6] [37], 

The reactions of acetylacetonato compounds of transition metals, such as Ni, Fe, Mo, Pt and Co, with R Al(OEt)3 cause parhal alkylahon and give the product with both alkyl and acetylacetonato ligands [44 9] (Eq. 5.13). 

The complexes formed via the above reactions can be regarded as an intermediate of peralkylation of di- or trivalent transition metal acetylacetonato compounds. 

In 1951, ferrocene was synthesized by Pauson [17] and Miller [18]. Soon after this synthesis, two groups led by Wilkinson and Fischer, independently reported that ferrocene has a stable carbon-iron 7r-bond [19]. This was the first example of a true organotransition metal complex containing a carbon-metal bond. Since then, numerous organotransition metal complexes have been prepared. The importance of these complexes as intermediates of many synthetic reactions has been discovered. More importantly, some transition metal complexes were found to behave as precursors of active catalysts. 

The industrial processes and related reactions described above, combined with the progress of organometallic chemistry, have stimulated further remarkable development in applying transition metal complexes to organic synthesis. Various novel synthetic methods, which are impossible by conventional means, have been discovered, bringing revolution in organic synthesis. 

Liebigs Ann. Chem., 582, 1 (1953) W. Reppe and H. Kroper, Liebigs Ann. Chem., 582, 38 (1953) Review of a historical account of chemistry of metal carbonyls, L. Mond, C. Langer and F. Quincke, J. Organometal. Chem., 383, 1 (1990). 

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