The mixed-metal carbonyl cluster anion [Os3Ir(CO)(13)](-): Synthesis, structure, reactivity and catalytic activity in the carbonylation of methanol

The cluster anion [Os3Ir(CO)(13)](-) (1) was prepared in 50% yield by react ion of Os-3(CO)(12) with [Ir(CO)(4)](-). The single-crystal X-ray structure analysis of the bis(triphenylphosphoranylidene)ammonium salt shows 1 to co nsist of a tetrahedral metal core with one of the 13 carbonyl ligands being bridging. Protonation of 1 led to the neutral cluster HOs3Ir(CO)(13) (2), whereas the hydrogenation gave the cluster anion [H2Os3Ir(CO)(12)](-) (3). The catalytic activity of 1 for the carbonylation of methanol was studied. Using CH3I as co-catalyst, catalytic turnover numbers up to 1800 were obtai ned (140 degrees C, 30 bar) within 14 h. (C) 1999 Elsevier Science B.V. All rights reserved.