Inelastic Neutron Scattering Studies of IrIH2(H2)(PPri3)2 and Neutron Diffraction Structure Determination of IrIH2(H2)(PPri3)2.cntdot.C10H8: Implications on the Mechanism of the Interconversion of Dihydrogen and Hydride Ligands

Abstract

We have now determined the molecular structure of IrIH{sub 2}(H{sub 2})(PPr{sup i}{sub 3}){sub 2} {center_dot} C{sub 10}H{sub 8} (2{center_dot}C{sub 10}H{sub 8}) through a single-crystal neutron diffraction study and carried out lNS studies on this complex. We report the result of these studies and their implications on the mechanism of dihydrogen/hydride interchange in the IrXH{sub 2}(H{sub 2})(PPr{sup i}{sub 3}){sub 2} complexes. Our results suggest that the interconversion of dihydrogen and hydride ligands in the IrXH{sub 2}(H{sub 2})(PPr{sup i}{sub 3}){sub 2} complexes is coupled to rotation of the dihydrogen ligand. Limbach et al. have proposed that the mechanism of hydride interchange in transition-metal trihydrides involves the rotation of an intermediate dihydrogen ligand. While it is not clear at this point if dihydrogen/hydride interconversion in the IrXH{sub 2}(H{sub 2})(PPr{sup i}{sub 3}){sub 2} complexes involves a bis(dihydrogen) intermediate, our results suggest that this process does not involve initial weakening of the dihydrogen H-H bond. 20 refs., 2 figs., 1 tab.