Ru-Based -Selective Metathesis Catalysts with Modified Cyclometalated Carbene Ligands.

A series of cyclometalated -selective ruthenium olefin metathesis catalysts with alterations to the -heterocyclic carbene (NHC) ligand were prepared. X-Ray crystal structures of several new catalysts were obtained, elucidating the structural features of this class of cyclometalated complexes. The metathesis activity of each stable complex was evaluated, and one catalyst, bearing geminal dimethyl backbone substitution, was found to be comparable to our best -selective metathesis catalyst to date.