Formation of a Silylated 1-Silaallene via an Intermediate 1-Chloro-1-silaallene

Twofold conjugate addition to a 2,6-dimesitylphenyl-substituted dihaloalkynylsilane yields a silyl-substituted 1-silaallene rather than the isomeric silyne. The dehalogenative intramolecular carbometalation elimination using t-BuLi proceeds via stepwise dehalogenation involving an intermediate 1-chloro-1-silaallene. Our findings are backed by crystal structure analyses, spectroscopic data, and ab initio calculations. The completely dehalogenated 1-silaallene provides a silyl group at the silaallene core itself, which should allow further functionalization.