Cyclic Bent Allene Hydrido-Carbonyl Complexes of Ruthenium: Highly Active Catalysts for Hydrogenation of Olefins

A new family of ruthenium complexes bearing the carbodicarbene-type ligand “cyclic bent allene” (CBA) have been synthesized from the common precursor RuHCl­(CO)­(PPh3)3. Complexes were evaluated for catalytic activity in the room-temperature hydrogenation of unactivated olefins and were found to be significantly more active than known ruthenium hydrido-carbonyl phosphine or NHC complexes. In particular, RuH­(OSO2CF3)­(CO)­(SIMes)­(CBA) was found to be among the most active hydrogenation catalysts, achieving comparable activity to Crabtree’s catalyst in the hydrogenation of unactivated trisubstituted olefins and superior activity in the hydrogenation of styrene derivatives in side-by-side catalytic runs. RuH­(OSO2CF3)­(CO)­(SIMes)­(CBA) was also found to be highly active in olefin selective hydrogenation in the presence of a variety of unsaturated functional groups, and can achieve exceptional diastereoselectivity in functional-group-directed hydrogenations at very low catalyst loadings.