Complexes of (hydroxylamido-O,N)molybdenum(VI). Preparation and crystal structures of dicesium bis(benzohydroximato)-cis-dioxomolybdate(VI) hydrate and of (benzohydroxamato)(benzohydroximato)(N,N-dimethylhydroxylamido-O,N)oxo- molybdenum(VI)

Article abstract of DOI:10.1021/ic50216a007

The reaction of cis-dioxobis(hydroxylamido-O,N)molybdenum(VI) complexes with benzohydroxamic acid in chloroform (or ethanol) affords monomeric neutral complexes containing benzohydroximato(2-) and benzohydroxomato(1-) ligands, the respective N-substituted hydroxylamido(1-) ligand, and a terminal oxo ligand. The complex [MoO((CH₃)₂NO)(BzH)Bz] (BzH = benzohydroxamate, Bz = benzohydroximate) has been characterized by a three-dimensional X-ray diffraction study. The complex crystallizes in the triclinic space group P1 (C_i¹, No. 2) with a = 9.063 (3) ?, b = 10.442 (4) ?, c = 10.618 (4) ?, α = 87.46 (3)°, β = 67.82 (3)°, γ = 76.71 (3)°, and V = 904 ?³; ρ_calcd = 1.628 g cm^-3 for Z = 2 and mol wt 443.3. Diffraction data were collected on a Syntex R 3 diffractometer using θ-2θ scan and Mo Kα radiation, and the structure was solved by conventional methods, resulting in a final R factor of 3.9% for 3819 independent reflections. The structure consists of monomeric complexes of Mo(VI) in a distorted pentagonal-bipyramidal environment containing an N,N-dimethylhydroxylamido-O,N ligand, one terminal oxo ligand, the O,O-coordinated dianion of benzohydroxamic acid (benzohydroximate), and an O,O-coordinated benzohydroxamato ligand. The reaction of molybdate(VI) anions with benzohydroxamic acid at pH ～9 yields the bis(benzohydroximato)-cis-dioxomolybdate(VI) anion. The cesium salt of the latter has been isolated and the structure has been determined by an X-ray analysis (experimental conditions as before). The complex crystallizes in the monoclinic space group P2₁ (C₂², No. 4) with a = 10.749 (4) ?, b = 12.357 (2) ?, c = 15.679 (3) ?, β = 107.65 (3)°, and V = 1985 ?³; ρ_calcd = 2.282 g cm^-3 for Z = 4 and mol wt 682.0. The structure was solved by conventional methods resulting in a final R factor of 4.2% for 5373 independent reflections. The structure consists of four complex dianions, [MoO₂Bz₂]^2- (two of which are crystallographically independent), eight cesium ions, and four molecules of water of crystallization per unit cell. The Mo(VI) ions are in a distorted octahedral environment of two terminal oxo groups in the cis position and of two benzohyroximato(2-) ligands per molybdenum(VI) center. The Mo-O bond distances in the trans position to terminal oxo groups in both structures are relatively longer because of a pronounced trans influence of the oxo ligands.