Isolation and interconversion of protic N-heterocyclic carbene and imidazolyl complexes:: Application to catalytic dehydrative condensation of N-(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-K(2)N,C) with AgNO(2) gives the nitrosyl-imidazolyl complex [Cp*Ru(NO)(L)][OTf] (OTf = OSO(2)CF(3)), 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.