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

The compounds Ir4(CO)11(R)­(μ-AuPPh3) (3, R = C6H5; 4, R = CH3; 5, R = 2-C16H10) were obtained from the reactions of [NEt4]­[Ir4(CO)11Br] with (R)­Au­(PPh3) (R = C6H5, CH3, 1-C16H10) at
25 °C by the loss of Br– and the oxidative
addition of the Au–C bond of the (R)­Au­(PPh3) to
the Ir4 cluster. Each compound contains a tetrahedral
Ir4 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 Ir4(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 Ir4(CO)9(PPh3)­(Ph)­(AuPPh3)3 (7) and
Ir4(CO)9(Ph)2(AuPPh3)4 (8). Compounds 6 and 8 both contain butterfly Au4(PPh3)4 clusters bridging a triangular face of a tetrahedral Ir4 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 Ir4 cluster. Compounds 6 and 8 were obtained in better yields from the reactions of Ir4(CO)11(AuPPh3)2 with (CH3)­Au­(PPh3) and PhAu­(PPh3), respectively.
Compound 7 was obtained independently in high yield by
the reaction of Ir4(CO)10(PPh3)­(AuPPh3)2 with PhAu­(PPh3). All of the new products
were characterized by single-crystal X-ray diffraction analyses.