The mixed-metal carbonyl cluster anion [Ru3Ir(CO)(13)](-): synthesis, molecular structure, fluxionality, reactivity

The new cluster anion [Ru3Ir(CO)(13)](-)1 was synthesized in high yield from [Ru-3(CO)(12)] and [Ir(CO)(4)(-). The single-crystal X-ray structure analysis of the bis(triphenylphosphoranylidene)ammonium salt revealed the presence of two isomers, [Ru3Ir(CO)(11)(mu-CO)(2)](-)1a and Ru3Ir(CO)(9)(mu-CO)(4)](-)1b in the same crystal. Both la and 1b present a tetrahedral Ru3Ir framework, differing only by the number of bridging carbonyl ligands. Variable-temperature C-13 NMR spectroscopic studies of 1 revealed the fluxionality of the carbonyl ligands and the interconversion of both isomers in solution. Protonation of 1 gave the neutral cluster [HRu3Ir(CO)(13)] 2,whereas reaction of 1 with molecular hydrogen yielded the anion [H2Ru3Ir(CO)(12)](-)3. Either hydrogenation of 2 or protonation of 3 gave [H3Ru3Ir(CO)(12)] 4. The tetrahedral structure of the hydride derivatives was confirmed by a single-crystal X-ray structure analysis of the bis(triphenylphosphoranylidene)ammonium salt of 3.