CP-ASTERISK-MOH5(PME3) - A CLASSICAL POLYHYDRIDE WITH A PENTAGONAL-BIPYRAMIDAL STRUCTURE AND A LONG T(1) RELAXATION-TIME

CpMoH5(PMe3) has been prepared from CP*MoCl2(PMe3) and LiAlH4. The co mpound is analogous to the previously reported CpWH5(PMe3) and CpWH5( PMe3) (Green, M. L. H.;Parkin, G. J. Chem. Soc., Chem. Commun. 1984, 1 467. Schrock, R. R.; et al. Organometallics 1986, 5, 1681) for which s tructural assignments were not made. A single sharp H-1-NMR resonance is observed for the five hydrides down to 183 K, consistent with eithe r a static symmetric structure or a highly fluxional structure, either classical or nonclassical. The measured minimum longitudinal relaxati on time, T1, is quite long (780 ms at 400 MHz and 230 K) and consisten t with a classical structure based on the pentagonal bipyramid which g ives rise to a substantially anisotropic moment of inertia.