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(N t Bu)2, Dipp = 2,6- i Pr-C6H3) toward various substituted internal alkynes was investigated. In contrast to previous reports that primarily yield [Si­(μ-C2)­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 [R1–CC–R2] (R1 = Ph or SiMe3, R2 = Ph or CCSiMe3) gave unconventional insertion into one of the amidinate ligands, followed by migration of the {N t Bu} group to bridge two Si atoms. This results in the formation of diverse expanded silacycles.