Polyazolyl Chelate Chemistry. 12.1 An Unusual Mode of Coordination for the Hydrotris(methimazolyl)borato Ligand

The reactions of [RuHCl(CO)(PPh 3 ) 3 ] or [RuH(NCMe) 2 (CO)(PPh 3 ) 2 ]ClO 4 with Na[HB(mt) 3 ] (mt = methimazolyl) provide the structurally characterized complex [RuH(CO)(PPh 3 ){κ 3 - H, S, S ‘ ‘-HB(mt) 3 }], which hydrogenates ethynylbenzene to styrene with formation of the ruthenaboratrane [Ru(CO)(PPh 3 ){B(mt) 3 }]( Ru→B ).