Carbenes mercury—carbon bonds

Examples of carbene insertions into the carbon-silicon bond of SCBs have been known since 1967, when Seyferth studied the behavior of SCBs exposed to dichlorocarbene, which was generated by thermolytic activation of phenyl(bromodichloromethyl)mercury <1967JA1538>. The reaction produces a mixture of products arising from Si-C and C-H bond insertions, with the major products being the ring-expanded silacyclopentanes that result from Si-C bond insertions (Scheme 30). 

Perfluoroalkyl anions, which form carbenes upon subsequent elimination of a-fluorine, may be generated by cleavage of the carbon-tin and carbon-mercury bonds in, for example, (trifluoromethyl)trimethyltin [56] and phenyl(trifluoromethyl)mercury [57] (Figure 6.40) under very mild conditions. Carbenes may be generated from... 

The principle underlying the use of organomercury compounds for carbene generation (entry 6, Scheme 8.1) is again the a-elimination mechanism. The carbon-mercury bond is much more covalent than the C-Li bond, however, so that the merciuy systems are generally stable at room temperature and easily isolated. They then decompose to the carbene when heated in solution with an appropriate alkene. The decomposition appears to be a reversible unimolecular reaction, and... 

---