Properties of the M—C bond

It is very often found that the metal-carbon bond is cleaved by halogens and less often by adds such as the hydrogen halides e.g. 

Where a j3-hydrogen atom is present in the alkyl group (e.g. ethyl, n-propyl, isopropyl), treatment with a hydride ion abstractor such as the triphenyl-methyl cation can lead to ethylenic cations, e.g. 

The formation of the 2-deuteropropene cation, 7.2, from the 2-isopropyl complex, 7.3, as shown above, confirms that the hydride is abstracted from a jS-carbon atom. Similarly, the thermal decomposition of the ethyl complex tr o -(Et3P)2PtCl(CH2CH3) to the hydride traas-(Et3P)2PtHCl and ethylene may proceed via internal abstraction of a hydro n from the j8-carbon, viz. 

Where the organic ligand has an unsaturated jS-carbon atom, e.g. metal a-allyl complexes, protonation can lead to 7r-olefinic cations, e.g. 

It may be envisaged that both the hydride abstraction and the protonation reactions proceed via the formation of a j3-carboninm ion intermediate which is stabilized by formation of an ethylene-metal bond and partial oxidation of the metal, e.g. 

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