Syntheses of Ir sub(4)(CO) sub(6)( eta super(5)-C sub(5)Me sub(4)H) sub(2) and Ir sub(7)( mu sub(3)-CO) sub(3)(CO) sub(12)( eta super(5)-C sub(5)Me sub(5)) from Pentametallic Molybdenum-Iridium Cluster Precursors

Reaction of Mo sub(2)Ir sub(3)( mu -CO) sub(3)(CO) sub(6)( eta super(5)-C sub(5)H sub(5)) sub(2)( eta u5C sub(5)Me sub(5)) with Ir(CO) sub(2)( eta super(5) -C sub(5)Me sub(4)H) afforded the four-valence-electron-deficient butterfly cluster Ir sub(4)(CO) sub(6)( eta super(5)-C sub(5)Me sub(4)H) sub(2); its stability has been rationalized with the aid of density functional theory calculations, which suggest that significant additional intracluster bonding alleviates the formal electron deficiency. Reaction of MoIr sub(4)(CO) sub(10)( eta super(5)-C sub(5)H sub(5)) ( eta super(5)-C sub(5)Me sub(5)) with [N(PPh sub(3)) sub(2)][Ir(CO) sub(4)] afforded the capped octahedral cluster Ir sub(7)( mu sub(3)-CO) sub(3)(CO) sub(12)( eta super(5)-C sub(5)Me sub(5)), which possesses three semi-face-capping CO ligands. These outcomes demonstrate that heterometallic clusters may serve as a potential source of new homometallic clusters following appropriate M-M' cleavage. Reactions of molybdenum-iridium clusters with iridium-containing reagents afforded new homometallic clusters. Ir sub(7)( mu sub(3)-CO) sub(3)(CO) sub(12)( eta super(5)-C sub(5)Me sub(5)) possesses three semi-face-capping CO ligands, while Ir sub(4)(CO) sub(6)( eta super(5)-C sub(5)Me sub(4)H) is formally very electron-deficient; theoretical studies suggest stabilization by significant intracluster multiple Ir-Ir bonding.