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 [Ru3(CO)12] and [AuCl(PPh3)]

Abstract

The new carbonyl cluster [PPh₄][Ir₇Ru₃(CO)₂₃] 1 has been obtained by the high yield reaction of [PPh₄]₂[Ir₆(CO)₁₅] with [Ru₃(CO)₁₂] in the presence of p-toluenesulfonic acid. The monoanionic decanuclear cluster 1 has an octahedral arrangement of the iridium atoms with three ruthenium atoms and an iridium atom tetrahedrally capping four triangular faces. Two terminal CO ligands are bound to each iridium atom and three to each ruthenium atom. In this synthesis p-toluenesulfonic acid served as a degradation reagent for [Ir₆(CO)₁₅]²⁻ to generate the capping {Ir(CO)₂}⁺ moiety. Reaction of 1 with [AuCl(PPh₃)] in the presence of AgOSO₂CF₃ at ambient temperature yielded the undecanuclear neutral cluster [Ir₇Ru₃(CO)₂₃(AuPPh₃)] 2. The {AuPPh₃}⁺ group co-ordinates to the apical iridium atom of the parent metal carbonyl monoanion 1 maintaining the cluster framework as well as the stereogeometry of the CO ligands. Thermal treatment of 1 with [AuCl(PPh₃)] 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.