Synthesis and characterization of some new complexes of the Vaska-type trans-[IrX(CO)L 2] (XCl or I; L=phosphite, phosphinite or phosphonite) and the direction of dihydrogen addition to these species

Abstract

A series of new Vaska-type complexes trans-[IrX(CO)L 2] (XCl, LP(OEt)Ph 2 ( 1), P(OEt) 2Ph ( 2), P(O- o-C 6H 4Ph) 3 ( 3), P(OPr i) 3 ( 4), P(OBu n) 3 ( 5); XI, LP(OEt)Ph 2 ( 6), P(OEt) 2Ph ( 7), P(O- o-C 6H 4Ph) 3 ( 8), P(OBu n) 3 ( 9) are prepared and characterized. In solution complex 8 undergoes slow cyclometallation to give [IrHI(CO){P(O- o-C 6H 3Ph)(O- o-C 6H 4Ph) 2} {P(O- o-C 6H 4Ph) 3}] ( 10). The oxidative addition of H 2 to 1–9 occurs stereospecifically with cis addition of H 2 parallel to the XIrCO axis rather than perpendicular to the axis, leading to cis, trans-[IrH 2X(CO)L 2] with a trans disposition of the two L ligands. This direction of H 2 addition is not in agreement with a prior suggestion based on ab initio quantum chemical calculations.