Widening the latency gap in chelated ruthenium olefin metathesis catalysts

The synthesis of novel sulfur-chelated ruthenium benzylidenes afforded latent catalysts with a wider range of activities and new isomeric forms. A ruthenium complex with a tridentate ligand displayed latency for even one of the most reactive ROMP monomers, dicyclopentadiene, while a room temperature latent trifluoromethyl-substituted thioether derivative was shown to be the most active sulfur-chelated precatalyst to date in several metathesis reactions at higher temperatures. These new complexes widen the spectrum of activity for this family of catalysts, enabling several practical applications and enhancing the understanding for the mechanisms of activation in strongly chelated ruthenium alkylidenes.