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

Abstract

Herein, we describe the facile and selective one-pot synthetic route to silylene-aluminum and silylene-gallium adducts. Reduction of silylene LSiCl (L = PhC(N^tBu)₂) with KC₈ in the presence of bulky and sterically hindered cyclopentadienyl aluminum Cp′′′AlCl₂ (Cp′′′ = 1,2,4-^tBu₃C₅H₂) and gallium [η¹-Cp′′′Ga(μ-Cl)Cl]₂ to afford the Lewis acid–base adducts η¹-Cp′′′M(Cl₂) ← 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′′′AlI₂ to form η¹-Cp′′′Al(I₂) ← 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^I. Compounds 1–3 are well characterized with NMR spectroscopic methods and single-crystal X-ray structural analysis.