Reactivity of a cationic N-heterocyclic carbene and its corresponding dicationic precursor

Detailed studies concerning the reactivity of the dicationic organometallic carbene precursor 1 and its related free cationic carbene 2 have been carried out. While dication 1 is stable in O-donor solvents like acetone, nitromethane and even water, it is degraded by softer nucleophiles like acetonitrile or electron rich aromatics. In contrast to the hydrolytic stability of dication 1, the cationic carbene 2a reacts readily with water to form the ring-opened formamide derivative 5a. The mechanism of the hydrolytic cleavage reaction was analysed by DFT calculations.