X-ray and neutron diffraction studies of tricarbonyl(.eta.-pentamethylcyclopentadienyl)hydridomolybdenum at 163 K

Abstract

The structure of [MoH([eta]-C[sub 5]Me[sub 5])(CO)[sub 3]] (1) has been determined by X-ray diffraction at 163(3) K [a = 6.969(2) [angstrom], b = 12.651(2) [angstrom], c = 7.954(2) [angstrom], [beta] = 103.36(2)[degrees], monoclinic, P2[sub 1]/m (No. 11), Z = 2] and neutron diffraction at 163.0(5) K [a = 6.968(2) [angstrom], b = 12.658(3) [angstrom], c = 7.953(2) [angstrom], [beta] = 103.34(2)[degrees]]. Refinements in space group P2[sub 1]/m against both data sets improved the description of the structure obtained by refinements in P2[sub 1] in this and an earlier study. The structure exhibits orientational disorder in the C[sub 5]Me[sub 5] group, yet relatively accurate geometric parameters have been obtained, with esd's from the neutron diffraction study of 0.007 [angstrom] for Mo-H, 0.010 [angstrom] (average) for C-H, and 0.003 [angstrom] (average) for all other bond lengths. The molecule adopts a [open quotes]four-legged piano stool[close quotes] geometry with the hydride ligand approximately trans to one of the Cp* ring carbons [Mo-H(1) = 1.789(7) [angstrom]]. Comparison of the title complex with related d[sup 4] CpMo(CO)[sub 3]L complexes (L = formally anionic, monodentate, [eta][sup 1] ligand) suggests that the conformation of these complexes is determined primarily b steric interactions between the ligand, L, and themore » Cp or Cp* ring, rather than by electronic effects of either Cp/Cp* or L.« less