Cationic Stannylenes: In Situ Generation and NMR Spectroscopic Characterization.

The reaction of NHC (NHC = 1,3,4,5-tetramethylimidazolylidene, where NHC = N-heterocyclic carbene) adducts to organotin(II) hydrides Ar*SnH and Ar'SnH [Ar* = 2,6-TripCH, where Trip = 2,4,6-triisopropylphenyl; Ar' = 2,6-MesCH, where Mes = 2,4,6-trimethylphenyl)] with Lewis acids such as B(CF) or [CPh] allows the abstraction of hydride and thus the generation of cationic, dicoordinate bis(σ-C)-substituted stannylenes [ArSn(NHC)]. The supposedly dicoordinate constitution of this cationic stannylene was investigated by NMR spectroscopy and further supported by density functional theory computations. For Ar'SnH(NHC), the generated cation was found to be inadequately sterically encumbered, allowing the formation of an adduct, [Ar'(NHC)Sn-Sn(H)(NHC)Ar'], which can be described as the protonated bis(NHC) adduct to the formal 1,2-distannyne.