Cationic Stannylenes: In Situ Generation and NMR Spectroscopic Characterization

The reaction of MeNHC (MeNHC = 1,3,4,5-tetramethylimidazolylidene, where NHC = N-heterocyclic carbene) adducts to organotin­(II) hydrides Ar*SnH and Ar′SnH [Ar* = 2,6-Trip2C6H3, where Trip = 2,4,6-triisopropylphenyl; Ar′ = 2,6-Mes2C6H3, where Mes = 2,4,6-trimethylphenyl)] with Lewis acids such as B­(C6F5)3 or [CPh3]+ 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(MeNHC), 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.