Ruthenium-Based Olefin Metathesis Catalysts Bearing N-Heterocyclic Carbene Ligands

A review has been reported that suggests that the application profile of the olefin metathesis catalysts can be controlled by a proper choice of a N-heterocyclic carbene ligand. Olefin metathesis has emerged as a powerful tool for the formation of C-C double bonds in organic synthesis. Since the metathesis process is neural and reversible, one can obtain a mixture of both substrates and products coexisting in a thermodynamical equilibrium. A spectacular progress in Ru-alkylidene catalyst design was achieved when N-heterocyclic carbenes (NHCs) were introduced as ancillary ligands. Stretching frequencies of NHC-containing carbonyl transition metal complexes were studied to quantify the electron density transfer from the NHC ligand to the metal. It is expected that the future development of new highly active catalysts with even better recyclability will help to overcome the crucial problem of ruthenium contamination in the pharmaceutical industry.