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

The X-ray crystal structure of [{(triphos)H(3−x)Ir}(μ-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}(μ-H)y{Au(PR3)}2][PF6]2 shows that each gold atom builds two Ir(μ2-H)Au bridges with the three hydrides of the ‘IrH3(triphos)’ building block; one Ir(μ3-H)Au2 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}(μ-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(μ2-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H bond in the trication [{(triphos)Ir (μ2-H)3{Au(PR3)}3}3+.