Synthesis and characterization of high-nuclearity iridium-ruthenium and -gold mixed-metal carbonyl clusters, [Ir7Ru3(CO)(23)](-), [Ir7Ru3(CO)(23)(AuPPh3)] and [Ir6Ru3(CO)(21)(AuPPh3)](-), possessing tetrahedrally capped octahedral iridium cores obtained by capping reactions with [Ru-3(CO)(12)] and [AuCl(PPh3)]

The new carbonyl cluster [PPh4][Ir7Ru3(CO)(23)] 1 has been obtained by the high yield reaction of [PPh4](2)[Ir-6(CO)(15)] with [Ru-3(CO)(12)] in the p resence of p-toluenesulfonic acid. The monoanionic decanuclear cluster 1 ha s an octahedral arrangement of the iridium atoms with three ruthenium atoms and an iridium atom tetrahedrally capping four triangular faces. Two termi nal CO ligands are bound to each iridium atom and three to each ruthenium a tom. In this synthesis p-toluenesulfonic acid served as a degradation reage nt for [Ir-6(CO)(15)](2-) to generate the capping {Ir(CO)(2)}(+) moiety. Re action of 1 with [AuCl(PPh3)] in the presence of AgOSO2CF3 at ambient tempe rature yielded the undecanuclear neutral cluster [Ir7Ru3(CO)(23)(AuPPh3)] 2 . The {AuPPh3}(+) group co-ordinates to the apical iridium atom of the pare nt metal carbonyl monoanion 1 maintaining the cluster framework as well as the stereogeometry of the CO ligands. Thermal treatment of 1 with [AuCl(PPh 3)] in refluxing 1,2-dichloroethane caused substitution of the capping {Ir( CO)(2)}(+) group in 1 with an isolobal {AuPPh3}(+) group, resulting in the formation of decanuclear monoanionic cluster [PPh4][Ir6Ru3(CO)(21)(AuPPh3)] 3.