A versatile rigid binucleating ligand for Rh2(μ-Cl)2 moieties: its application as a catalyst in hydrogenation and cyclopropanation: Crystal structure of [Rh(C5Me5)Cl{7,8-μ-S(4′-C6H3(CH3))S-C2B9H10}][7,8-μ-S(4′-C6H3(CH3))S-C2B9H10]·THF

A rigid non-deforming “MCl2M” binucleating ligand [7,8-μ-S(4′-C6H3(CH3))S-C2B9H10]− able to held the two rhodium atoms in a cooperative distance has been synthesized. The original two bridging chlorides are retained in [Rh2(C5Me5)2Cl2{7,8-μ-S(4′-C6H3(CH3))S-C2B9H10}]+. Hydrogenation of 1-hexene is 10 times faster with [Rh2(C5Me5)2Cl2{7,8-μ-S(4′-C6H3(CH3))S-C2B9H10}]+ than with [Rh2(C5Me5)2Cl4]. A hydrogenation mechanism has been proposed which assumes that [Rh2(C5Me5)2(Cl)(H){7,8-μ-S(4′-C6H3(CH3))S-C2B9H10}]+ is the first generated species in the process.