One silicon atom of bis(silylene) functions as a selective Lewis base under adduct formation with a Lewis acid.

Herein, we describe the facile and selective one-pot synthetic route to silylene-aluminum and silylene-gallium adducts. Reduction of silylene LSiCl (L = PhC(NBu)) with KC in the presence of bulky and sterically hindered cyclopentadienyl aluminum Cp'''AlCl (Cp''' = 1,2,4-BuCH) and gallium [η-Cp'''Ga(μ-Cl)Cl] to afford the Lewis acid-base adducts η-Cp'''M(Cl) ← Si(L)-SiL (M = Al, 1; M = Ga, 3). To confirm the formation of the Lewis acid-base adduct, the bis(silylene) LSi(I)-Si(I)L reacts with Cp'''AlI to form η-Cp'''Al(I) ← Si(L)-SiL (2). These are the first examples where one Si atom in the bis(silylene) is a Lewis base and coordinates with aluminum or gallium to form a Lewis acid-base adduct, while the other Si atom in the bis(silylene) still maintains the characteristics of silylene. Compound 3 was heated to 70 °C in toluene for 4 hours and decomposed into the silylene LSiCl and Cp'''Ga. Compounds 1-3 are well characterized with NMR spectroscopic methods and single-crystal X-ray structural analysis.