Bismuth-stabilized alkylation

The M—M bonds in R3MMR3, R3M(R2M) MR3 or (R2M) for M = Sn, Pb are cleaved by water, alcoholic solution of AgN03, alkyl iodides, mercury and bismuth halides and are oxidized by air. In contrast, these compounds with M = Si, Ge are stable under similar reaction conditions. The stability of the highly reactive R2M=MR2, as well as the tendency of R2M to dimerize, diminish as the atomic number of M increases160-162. 

The chemistry of carbanions stabilized by the heavy main group elements has been extensively investigated by Kauffmann, and a thorough description of his work can be found in a recent review. There are many similarities between the elements. The anions stabilized by the heavy main group elements listed above can generally be alkylated, and in some cases their reaction with carbonyl compounds is a useful alternative to the Wittig reaction. All the stabilized metallomethyl lithium anions (except bismuth) exhibit marked thermal stability. 

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