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

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journal contribution
posted on 14.05.2012, 00:00 by Richard D. Adams, Mingwei Chen, Xinzheng Yang
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 13 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)93-PPhC6H4)­(AuPPh3)2, 5, which contains a triply bridging PPhC6H4 ligand.