Synthesis and Structures of Iridium-Gold Carbonyl Cluster Compounds Containing Methyl and σ-Aryl Ligands

The compounds Ir-4(CO)(11)(R)(mu-AuPPh3) (3, R = C6H5; 4, R = CH3; 5, R = 2-C16H10) were obtained from the reactions of [NEt4][Ir-4(CO)(11)Br] with (R)Au(PPh3) (R = C6H5, CH3, 1-C16H10) at 25 degrees C by the loss of Br- and the oxidative addition of the Au-C bond of the (R)Au(PPh3) to the Ir-4 cluster. Each compound contains a tetrahedral Ir-4 cluster with an Au(PPh3) group bridging one of the six Ir-Ir bonds and a R group coordinated to one of the Au-bridged Ir atoms. The reaction of (CH3)Au(PPh3) with [PPN][HIr4(CO)(11)] yielded compound 4 and the higher nuclearity compound Ir-4(CO)(9)(CH3)(2)(AuPPh3)(4) (6). The reaction of PhAu(PPh3) with [PPN][HIr4(CO)(11)] yielded compound 3 and the higher nuclearity compounds Ir-4(CO)(9)(PPh3)(Ph)(AuPPh3)(3) (7) and Ir-4(CO)(9)(Ph)(2)(AuPPh3)(4) (8). Compounds 6 and 8 both contain butterfly Au-4(PPh3)(4) clusters bridging a triangular face of a tetrahedral Ir-4 cluster and a CH3 group or Ph group, respectively, on two neighboring Ir atoms. Compound 7 contains a triangular (AuPPh3)(3) group bridging a triangular face of a tetrahedral Ir-4 cluster. Compounds 6 and 8 were obtained in better yields from the reactions of Ir-4(CO)(11)(AuPPh3)(2) with (CH3)Au(PPh3) and PhAu(PPh3), respectively. Compound 7 was obtained independently in high yield by the reaction of Ir-4(CO)(10)(PPh3)(AuPPh3)(2) with PhAu(PPh3). All of the new products were characterized by single-crystal X-ray diffraction analyses.