Synthesis and Characterization of OsX{NHC(Ph)C6H4}H2(PiPr3)2 (X = H, Cl, Br, I): Nature of the H2 Unit and Its Behavior in Solution

Abstract

The hexahydride OsH6(PiPr3)2 (1) reacts with benzophenone imine to give the trihydride derivative (2). The three hydride ligands and the bidentate group of 2 are situated in the equatorial plane of a pentagonal-bipyramidal arrangement of ligands around the metallic center. In solution, two thermally activated exchange processes take place between these hydride ligands, one of them faster than the other one. The reaction of 2 with HCl leads to OsH3Cl(NHCPh2)(PiPr3)2 (3), which evolves in solution into the elongated dihydrogen compound (4). Complex 4 and the related compounds (X = Br (5), I (6)) can be also prepared by protonation of 2 with HBF4·OEt2 in dichloromethane and subsequent treatment with NaX (X = Cl, Br, I). The structure of 4 has been determined by X-ray diffraction. The geometry around the osmium atom can be described as a distorted octahedron, with the triisopropylphosphine ligands occupying two relative trans positions. The remaining perpendicular plane is formed by the mutually cis disposed ...