Dynamic behaviour, solution and crystal structure of an allylmolybdenum/oxo/hydroxo heterocubane

The synthesis of a highly unsymmetrical, chiral oxometallocubane anion [{(p i -C3H5)Mo(CO)(2)}(4)(mu (3)-OH)(3)(mu (3)-O)](-) built up from organometal lic moieties and oxo ligands is described. Its structure was investigated n ot only in the solid state (X-ray diffraction analysis) but also in solutio n applying modem sophisticated NMR techniques. It was thereby possible to i dentify a trigonal twist rearrangement as the process responsible for the f luxional behaviour of this compound in solution: the (pi -allyl)Mo moieties are highly mobile, rotating on the "oxo surface" even at -65 degreesC. Thi s complex can be regarded as a suitable model for (pi -allyl)Mo units incor porated into molybdenum oxide surfaces.