Possible Pi-Complex Intermediates in the Reaction of Disilenes with Mercury(II) Trifluoroacetate

摘要

The well-known reaction of mercury(II) compounds with alkenes is generally believed to involve formation of a Pe-complex mercurinium ion in the initial step. Mercurinium ions have been observed by n.m.r. spectroscopy in superacid solvents at low temperatures, and for special cases in other polar solvents. On the other hand the n.m.r. spectra of mixtures of simple alkenes with mercury(II) trifluoroacetate (1) in benzene indicate that the initial reaction product is a o-bound species, (2) Also Fukuzumi and Kochi have shown that alkenes form weak charge-transfer complexes with mercury salts in dichloromethane. The reaction of mercury(II) trifluoroacetate with disilenes and in tetrahydrofuran at 25 C produces 1,2-bis(trifluoroacetoxy) disilanes (5) and (6a,b); below -15 C, n.m.r. spectra indicate that an intermediate is formed, for which structures (7) and (8a,b) are proposed.