Synthesis of Mo(V) Dimers of the Form [Mo2O2(acac)2(μ-O)(μ-OC2H5)(μ-O2CR)], the Tetramer [Mo2O2(acac)2(μ-O)(μ-OC2H5)(μ-O2C)C6H4(p-μ-O2C) Mo2O2(acac)2(μ-O)(μ-OC2H5)], and, the Crystal and Molecular Structures of [Mo2O2(acac)2(μ-O) (μ-OC2H5)(μ-OOCC6H5)] and [Mo2O2(acac)2(μ-O) (μ-OC2H5)(μ-OOCC6H4(0-OH))]

Reaction of bis(acetylacetonato)dioxomolybdenum(VI) (MoO2(acac)(2)) with benzoic acid, in ethanol, yielded an oxo, ethoxide and benzoate-bridged dinuclear Mo(V) species Mo2O2(acac)(2)(mu-O)(mu-OC2H5)(mu-OOCC6H5) (1), with two terminal "MoO" units and one acac ligand retained on each Mo atom. This complex was analysed by IR and H-1 NMR spectroscopy, X-ray crystallography and elemental analyses. The same reaction with substituted benzoic acids (o-OH)C6H4- COOH, (p-Cl)C6H4COOH, (2,4-(OH)(2))C6H3COOH and (o-I)C6H4COOH produced a series of dinuclear complexes, all of which were characterized by IR and I H NMR spectroscopy and elemental analyses. Terephthalie acid ((p-COOH)C6H4(COOH)) on reaction with MoO2(acac)(2) resulted in a tetramer [Mo2O2(acac)(2)(mu-O) (mu-OC2H5)(mu-O2C)C6H4(p-mu-O2C)Mo2O2(acac)(2)(mu-O)(mu-OC2H5)] (6) which was evident from the H-1 NMR spectrum and elemental analyses. The role of ethanol as a reducing agent has proved instrumental in the synthesis of these dimeric Mo(V) complexes. The synthetic details and characterization by spectroscopic and X-ray crystallographic techniques are discussed.