Isolation and Interconversion of Protic<i></i> N-Heterocyclic Carbene and Imidazolyl Complexes: Application to Catalytic Dehydrative Condensation of <i>N</i>-(2-Pyridyl)benzimidazole and Allyl Alcohol

Treatment of the protic N-heterocyclic carbene (NHC) complex [Cp*RuCl(LH)] (2; LH = N-(2-pyridyl)benzimidazolin-2-ylidene-κ2N,C) with AgNO2 gives the nitrosyl–imidazolyl complex [Cp*Ru(NO)(L)][OTf] (OTf = OSO2CF3), which undergoes reversible protonation to afford the NHC complex [Cp*Ru(NO)(LH)][OTf]2. The bifunctional complex 2 also catalyzes the dehydrative condensation of N-(2-pyridyl)benzimidazole and allyl alcohol, leading to the formation of trans- and cis-2-(1-propenyl)-N-(2-pyridyl)benzimidazole.