Synthesis of the carbido anion [Os5C(CO)15I]? and the X-ray crystal structures of Os5C(CO)15 and [(Ph3P)2N][Os5C(CO)15I]

Os5C(CO)15 has been shown to be isostructural (but not isomorphous) with its iron analogue Fe5C(CO)15 which has a square pyramidal metal geometry and its reaction with iodide gives the anion [Os5C(CO)15I]– in which the osmium atoms have opened out to a bridged butterfly arrangement; the flexibility of the cluster units in reversibility towards electron donation is illustrated.