Synthesis of Mo(V) Dimers of the Form [Mo \u3c inf\u3e 2 O \u3c inf\u3e 2 (acac) \u3c inf\u3e 2 (μ-O)(μ- OC \u3c inf\u3e 2 H \u3c inf\u3e 5 )(μ-O \u3c inf\u3e 2 CR)], the Tetramer [Mo \u3c inf\u3e 2 O \u3c inf\u3e 2 (acac) \u3c inf\u3e 2 (μ-O)(μ- OC \u3c inf\u3e 2 H \u3c inf\u3e 5 )(μ-O \u3c inf\u3e 2 C)C \u3c inf\u3e 6 H \u3c inf\u3e 4 (p-μ-O \u3c inf\u3e 2 C)Mo \u3c inf\u3e 2 O \u3c inf\u3e 2 (acac) \u3c inf\u3e 2 (μ-O)

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(μ-O)(μ- OC2H5)(μ-OOCC6H5) (1), with two terminal MoO units and one acac ligand retained on each Mo atom. This complex was analysed by IR and 1H NMR spectroscopy, X-ray crystallography and elemental analyses. The same reaction with substituted benzoic acids (o-OH)C6H4COOH, (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 1H NMR spectroscopy and elemental analyses. Terephthalic acid ((p-COOH)C6H4(COOH)) on reaction with MoO2(acac)2 resulted in a tetramer [Mo2O2(acac)2(μ-O)(μ- OC2H5)(μ-O2C)C6H4(p-μ-O 2C)Mo2O2(acac)2(μ-O)(μ -OC2H5)] (6) which was evident from the 1H 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. © 2010 Springer Science+Business Media, LLC

Synthesis and characterisation of new molybdenum - oxo complexes containing diphenylphosphinylacetic acid and 2-(tert-butylsulphoxide)phenyldiphenylphosphine oxide as bidentate ligands

Reaction of the ligands diphenylphosphinylacetic acid Ph2P(O)CH2COOH (1) and 2-(tert-butylthio)phenyldiphenylphosphine oxide Ph2P(O)C6H4tBuS (2) with MoO2Cl2 , resulted in two complexes MoO2Cl2Ph2P(O)CH2COOH (3) and MoO2Cl2Ph2P(O)C6H4tBuS(O) (4). Complexes 3 and 4 were isolated and analysed by 1H NMR, 31P NMR and X-ray crystallography. Complex 3 crystallised with a molecule of the free ligand in a 1:1 ratio (3·1) and complex 4 crystallised with molecules of the solvent CH2Cl2 within the unit cell in a 2:1 ratio (4·0.5CH2Cl2). Tetrameric arrangements comprised of hydrogen bonds were observed in complexes 1 and 3. Complex 4 exhibited a seven-membered ring structure owing to the oxidation of the sulphide in 2 to sulphoxide and coordination of this ligand via the oxygen atoms to the molybdenum atom. © 2010 Elsevier B.V. All rights reserved

Rational synthesis of molybdenum(V) tetramers consisting of [Mo \u3c inf\u3e 2 O \u3c inf\u3e 4 ] \u3c sup\u3e 2+ \u3c/sup\u3e dimers held together by bridging phosphinate ligands and the tungsten(VI) dimer [(CH \u3c inf\u3e 3 O) \u3c inf\u3e 2 (O)W(μ-O)(μ-O \u3c inf\u3e 2 PPh \u3c inf\u3e 2 ) \u3c inf\u3e 2 W(O) (CH \u3c inf\u3e 3 O) \u3c inf\u3e 2 ]: Structural and theoretical considerations

Reacting MoO2(acac)2 with Ph2POOH or Me2POOH in EtOH results in the formation of the tetranuclear molybdenum (V) clusters Mo4(μ 3-O)4(μ- O2PR2)4O4, PR2 = PPh 2, 1, or PMe2, 2, in functional yields (\u3e 90% and 55% respectively). The reaction of WO2(acac)2 with Ph 2POOH in MeOH affords the tungsten dimer [(CH3O) 2(O)W(μ-O)(μ-O2PPh2)2W(O) (CH3O)2], 3. The single crystal X-ray determined structures of complexes 1-3 are reported. In 1 and 2, the four Mo=O units are interconnected by four triply bridging oxygen atoms, resulting in a distorted cubic-like structure for the Mo4(μ 3-O) 4O4 units. Each molybdenum atom forms two additional Mo-O bonds with two oxygen atoms from different adjacent phosphinato ligands. Complex 3, a tungsten dimer, contains packing disorder and consists of bridging oxo and diphenylphosphinato ligands. The bonding of 1 and 2 assessed by density-functional methods showed that bonding between the Mo(V) centers occurs through σ overlap of the d xy orbitals. © 2007 Springer Science+Business Media, LLC