The transition metal to carbon sigma bond

Abstract

On account of the apparent instabilities or difficulties in isolating simple alkyls of transition metals it has commonly been assumed firstly that the bond strength is low and secondly that the presence of it-acid ligands such as CO, R3P, it-C5H5, etc. on the metal are necessary for the existence of stable metal— carbon cr-bonds. Although only a few bond strengths have been estimated, and these in compounds with other ligands present, there is no sound reason for assuming that the metal to carbon bond strengths are low. The reason for the instability of simple transition metal alkyls, M—R, generally is to be sought in the available possible pathways for decomposition reactions of the alkyls such as hydrogen transfer from a or 3-carbon atoms of the alkyl chain alkene and/or alkane elimination reactions, etc. The synthesis of elimination—stabilized alkyls of transition metals in high oxidation states is discussed and illustrated primarily by consideration of trimethylsilylmethyl derivatives, from which alkene elimination is impossible due to the incapacity for forming silicon to carbon double bonds. The chemical properties and structures of compounds M(CH2SiMe3) where M =yIV, Cr', Mo, W etc., and of other related species are described together with appropriate infrared, nuclear magnetic resonance and electron spin resonance