Synthesis of Oxygen- and Sulfur-Bridged Dirhodium Complexes and Their Use As Catalysts in the Chemoselective Hydrogenation of Alkenes

Oxygen-bridged and sulfur-bridged rhodium homobimetallic complexes were synthesized as air-stable crystals by using 2,6-bis(phosphanylmethyl)phenolate and -thiophenolate as the ligands, respectively. The oxygen-bridged dirhodium complex has a symmetrical structure where the carbon atom at the <i>ipso</i> position, oxygen, and two rhodium atoms are located in the same plane. It is thermally stable compared to the sulfur-bridged dirhodium complex and shows catalytic activity for hydrogenation of alkenes with high chemoselectivity.