SOLUTION DYNAMICS AND CRYSTAL-STRUCTURE OF CPMOOS3(CO)10(MU-H)2[MU-3-ETA-2-C(O)CH2TOL]

Abstract

The tetranuclear heterometallic complex CpMoOs3(CO)10(mu-H)2[mu3-eta2-C(O)CH2Tol] (1, Cp=eta5-C5H5, Tol=p-C6H4Me) has been examined by variable-temperature C-13-NMR spectroscopy and by a full three-dimensional X-ray structural analysis. Complex 1 crystallizes in the orthorhombic space group Pna2(1) with a = 12.960(1) angstrom, b = 11.255(1) angstrom, c = 38.569(10) angstrom, V = 5626(2) angstrom3 and rho(calcd) = 2.71 gcm-3 for Z = 8 and molecular weight 1146.9. Diffraction data were collected on a CAD4 diffractometer, and the structure was refined to R(F) = 9.7% and R(W)F = 9.9% for 2530 data (MoKalpha radiation). There are two essentially equivalent molecules in the crystallographic asymmetric unit. The tetranuclear molecule contains a triangulated rhomboidal arrangement of metal atoms with Os(2) and Mo at the two bridgehead positions. The metal framework is planar; the dihedral angle between Os(1)-Os(2)-Mo and Os(3)-Os(2)-Mo planes is 180-degrees. A triply bridging (nu3, eta2) acyl ligand lies above the Os(1)-Os(2)-Mo plane; the oxygen atom spans the two bridgehead positions, while the carbon atom spans one bridgehead position and an acute apical position. The molecular architecture is completed by an eta5-cyclopentadienyl ligand and a semi-triply bridging carbonyl ligand on the molybdenum atom, and nine terminal carbonyl ligands-four on Os(3), three on Os(1), and two on Os(2). The two hydride ligands are inferred to occupy the Os(1)-Os(2) and Mo-Os(3) edges from structural and NMR data.