Expanding the chemistry of cationic N-heterocyclic carbenes: alternative synthesis, reactivity, and coordination chemistry.

A new synthetic route to complexes of the cationic N-heterocyclic carbene ligand 2 has been developed by the attachment of a cationic pentamethylcyclopentadienylruthenium (RuCp*) fragment to a metal-coordinated benzimidazol-2-ylidene ligand. The coordination chemistry and the steric and electronic properties of the cationic carbene were investigated in detail by experimental and theoretical methods. X-ray structures of three carbene-metal complexes were determined. The cationic ligand 2 is a poorer overall electron donor relative to the related neutral carbene, which is evident from cyclic voltammetry (CV) and IR measurements.