Unconventional Insertions of Internal Alkynes into a Mixed-Valent Silaiminyl-Silylene.

The reactivity of a mixed-valent silaiminyl-silylene [LSi-Si(NDipp)L] (L = PhC(NBu), Dipp = 2,6-Pr-CH) toward various substituted internal alkynes was investigated. In contrast to previous reports that primarily yield [Si(μ-C)Si]-modified rings via 1,2-addition of two silylenes in the center of the molecule, our study reveals a novel reaction pathway. The introduction of [R-C≡C-R] (R = Ph or SiMe, R = Ph or C≡CSiMe) gave unconventional insertion into one of the amidinate ligands, followed by migration of the {NBu} group to bridge two Si atoms. This results in the formation of diverse expanded silacycles.