A Novel Class of Ruthenium Catalysts for Olefin Metathesis.

The different nature of carbene ligands is clearly demonstrated by the first ruthenium-based complexes 1, which contain both alkylidene and N-heterocyclic carbene moieties. The latter exhibit a pronounced Lewis base behavior. Moreover, this difference forms the basis of the high catalytic activities of these compounds in olefin metathesis reactions.