Structural studies of the hydride-bridged iridium gold complexes 'IrHm{CH3C(CH2PPh2)3}{Au(PR3)}n'

The X-ray crystal structure of [{(triphos)H(3-x)Ir}(mu-H)(x) {Au(PR3)}][PF6] (triphos = CH3C(CH2PPh2)(3), x = 2) shows that the gold atom builds two almost equal Ir-H-Au bridges with the he'IrH3(triphos)' building block. The Ir-H-Au bridging parameters are typical of three-center-two-electron interactions. The X-ray crystal structure of [{(triphos)H(3-y)Ir}(mu-H)(y) {Au(PR3)}(2)][PF6](2) shows that each gold atom builds two Ir(mu(2)-H)Au bridges with the three hydrides of the 'IrH3(triphos)' building block; one Ir(mu(3)-H)Au-2 bridge is also present (y = 3). The relative positions of the Ir, H, Au and P atoms show that typical three-center-two-electron interactions predominate in this compound, in which there is no direct Au-Au bonding. The neutron diffraction structure of [{(triphos)Ir}(mu-H)(2){Au(PPh3)}(3)][PF6](2) confirms the earlier hypothesis that only two of the three Ir-Au edges are associated with a hydride with formation of Ir(mu(2)-H)Au bridges. The presence or absence of the latter ligand changes the Ir-Au distance only marginally, in contrast to the general trend in hydride clusters. It is shown that the formation of a 'classical' cluster in this set of compounds requires a quadrimetallic unit and the two additional electrons generated by loss of a proton from an Ir-fl bond in the trication [{(triphos)Ir (mu(2)-H)(3){Au(PR3)}(3)}(3+). (C) 2000 Elsevier Science S.A. All rights reserved.