Reactivity of an NHC-Stabilized Silylene towards Lewis Acids and Lewis Bases

The reactivity of N-heterocyclic carbene stabilized (NHC-stabilized) aminochlorosilylene ArN(SiMe3)Si(IiPr)Cl (1, Ar = 2,6-iPr2C6H3, IiPr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with selected Lewis acids and Lewis bases is described. Treatment of 1 with BH3·THF yielded 1·BH3 (2) quantitatively. Compound 2 is a rare example of an air-insensitive silylene–borane adduct showing both acidic and basic properties of chlorosilylene in a single molecule. Crystals of 1–(CH2)3CH2OB(C6F5)3 (3) were obtained from the reaction of 1 with B(C6F5)3 in THF. For the first time, a frustrated Lewis pair (FLP) composed of a silylene and a substituted borane was observed to activate small molecules. Reaction of 1 with IMe4 (IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) at room temperature afforded silylene ArN(SiMe3)Si(IMe4)Cl (4), which represents a rare example of an NHC-stabilized silylene synthesized through ligand exchange.