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

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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 (> 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.

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Journal of Cluster Science