Synthesis and Striking Reactivity of an Isolable Tetrasilyl-Substituted Trisilaallene

The first silyl-substituted Si 3 -allene, namely 1,1,3,3-tetrakis(di- tert -butylmethylsilyl)trisilaallene ( 4 ), was prepared as an air- and moisture-sensitive red solid by the reaction of the dilithiosilane ( t Bu 2 MeSi) 2 SiLi 2 with the dichlorosilylene–NHC complex:SiCl 2 ←NHC (NHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) in benzene at room temperature. Remarkably, the reaction of 4 with methanol proceeds regioselectively to form only the 3,3-dimethoxypentasilane derivative 5, in contrast to the case for a previously reported trisilaallene. In addition, 4 undergoes unprecedented thermal isomerization to tetrakis(di- tert -butylmethylsilyl)cyclotrisilene ( 7 ).