Reactivity of a Zwitterionic Stable Silylene toward Halosilanes and Haloalkanes

The insertion of the thermally stable ylide-like silylene LSi: (1) {L = CH[(CCH2)CMe][N(Ar)]2], Ar = 2,6-iPr2C6H3} into C−X and Si−X bonds of various small haloalkanes and halosilanes (MeI, PhCH2Br, CH2Cl2, CH2ClI, CH2Br2, CHCl3, MeCCl3, HSiCl3, and MeSiCl3) has been investigated. Surprisingly, the outcome of the reactions is in marked contrast to previous results employing related isolable silylenes. Exclusive formation of 1,1-insertion products LSi(R)X is observed, in a few cases along with a small amount of dihalosilane LSiX2 or monohalosilane LSi(H)X. It is proposed that the reaction occurs via polar 1,4-addition and subsequent rearrangement of the latter kinetic (initial) product to give the 1,1-insertion product. The new compounds have been characterized by 1H, 13C, and 29Si NMR spectroscopy and by single-crystal X-ray diffraction analyses.