Iridium–Gold Cluster Compounds: Syntheses, Structures, and an Unusual Ligand-Induced Skeletal Rearrangement

Abstract

The new iridium–gold complex Ir4(CO)11(Ph)(μ-AuPPh3), 1 was obtained from the reaction of the tetrairidium anion [Ir4(CO)11(Ph)]− with [Au(PPh3)][NO3]. Two new iridium–gold complexes Ir4(CO)10(AuPPh3)2, 2, and Ir4(CO)11(AuPPh3)2, 3, were obtained from the reaction of [HIr4(CO)11]− with [Au(PPh3)][NO3]. Compounds 1–3 were structurally characterized by single crystal X-ray diffraction analyses. Compound 2 adds CO reversibly to form compound 3. In this process, the octahedral Ir4Au2 cluster of 2 is converted into the Au(PPh3)-capped Ir4Au trigonal bipyramidal cluster found in 3. Compounds 2 and 3 have been investigated by DFT computational analyses in order to understand the metal–metal bonding and the mechanism of their interconversion by CO addition and elimination. Compound 2 adds PPh3 to form the compound Ir4(CO)10(PPh3)(AuPPh3)2, 4, which is structurally similar to 3. Compound 4 loses CO and benzene when heated to form the compound Ir4(CO)9(μ3-PPhC6H4)(AuPPh3)2, 5, which contains a triply bridging PPhC6H4 ligand.