Syntheses of the seven-metal [nickel-osmium] carbide cluster [PPN]2[Os3Ni4C(CO)15] and of [PPN]2[Os3Ni3C(CO)13

Abstract

Clusters containing Ni, Pd, and Pt often have fewer electrons for their geometries than predicted by traditional electron-counting rules such as the polyhedral skeletal electron pair theory (PSEPT). For example, [Pt[sub 3](CO)[sub 6]] has only 44 electrons, although PSEPT predicts that it should be a 48-electron cluster. Extended Hueckel calculations on the 48-electron cluster Fe[sub 3](CO)[sub 12] show that 9 predominantly s and p metal orbitals and 3 d orbitals interact with the 12 CO ligands to give 24 filled cluster orbitals. In [Pt[sub 3](CO)[sub 6]][sup 2[minus]] only 22 cluster orbitals are filled, because two high-lying e[double prime] orbitals do not interact with CO ligands to form bonding orbitals. Similarly, in heterometallic clusters, the replacement of an M(CO)[sub 3] fragment with an isolobal PtL[sub 2] fragment may result in a decrease in the number of electrons required for a closed-shell configuration, but many heterometallic Pt clusters, for example Pt[sub 2]Os[sub 4](CO)[sub 12](COD)[sub 2] (COD = 1,5-cyclooctadiene), obey traditional electron-counting rules such as PSEPT. The ketenylidene clusters [PPN][sub 2][M[sub 3](CO)[sub 9]CCO] react through redox condensation to form a variety of mixed-metal carbide clusters. The authors report here the redox condensation of [PPN][sub 2][Os[sub 3](CO)[sub 9]CCO] and Ni(CO)[sub 4] to form themore » seven-metal, 100-electron carbide cluster [PPN][sub 2][Os[sub 3]Ni[sub 4]C(CO)[sub 15]].« less