Olefin metathesis ruthenium catalysts with unsaturated NHC

"Second-generation" Ru-carbene complexes bearing one unsaturated nucleophilic imidazolin-2-ylidene ligand with broad variation of the alkylidene fragment are available via ethylidene complex RuCl2(=CH-Me)(PCy3)2 under very mild conditions. The synthesis and the first applications of new ruthenium complexes containing new aromatic and heteroaromatic units attached to the alkylidene bond are described. It is shown that improvements in activity of the ruthenium carbene complexes can be achieved by incorporation of methyl groups in 4,5-position of imidazol-2-ylidene moiety independent from alkylidene fragment.