Mixed μ-phosphido or μ-thiolato μ-halo-dimolybdenum(III) compounds [Mo2Cp2(μ-SMe)2(μ-X)(μ-Y)] (X=PPh2, Y=Cl; X=SCH3, Y=Br, I): Electrochemical and structural comparisons – The X-ray structure of [{Mo2Cp2Br(μ-O)(μ-SMe)2}2(μ-MoO4)]

Abstract : Mixed μ-phosphido or μ-thiolato μ-halo-dimolybdenum(III) compounds [Mo2Cp2(μ-SMe)2(μ-X)(μ-Y)] (X = PPh2, Y = Cl (1); X = SCH3, Y = Br (3), I(4)) have been studied. Syntheses and X-ray structures of the new bromo and iodo analogues of [Mo2Cp2(μ-SMe)3(μ-Cl)] (2) are reported. While preparing 3 a side-product 5 was obtained and structurally characterised as the Mo5 system [{Mo2Cp2Br(μ-O)(μ-SMe)2}2(μ-MoO4)], containing a {MoIV–MoIV–O–(MoVIO2)–O–MoIV–MoIV} unit. The influence of the bridging groups on the structures and electrochemical behaviour of the complexes [Mo2Cp2(μ-SMe)2(μ-X)(μ-Y)] 1–4 has been investigated. In MeCN–[NBu4][PF6] the first oxidation of [Mo2Cp2(μ-SMe)2(μ-PPh2)(μ-Cl)] (1) is quasi-reversible, contrasting with the essentially irreversible first oxidation of the thiolate analogue [Mo2Cp2(μ-SMe)3(μ-Cl)] (2) under similar conditions. The effects of lowering the temperature or increasing the scan rate on the oxidation of 1 were examined: the initial quasi-reversible oxidation at first became irreversible but at still higher scan rates or lower temperatures the oxidation was again quasi-reversible. This suggests that the oxidation of 1 in MeCN is followed by reversible coordination of acetonitrile to afford the species [Mo2Cp2(μ-SMe)2(μ-PPh2)(Cl)(MeCN)]+ (7+). Cyclic voltammetry of [Mo2Cp2(μ-SMe)3(μ-Y)](Y = Br (3) or I (4)) showed two quasi-reversible diffusion-controlled oxidation steps in CH2Cl2–[NBu4][PF6] or thf–[NBu4][PF6]. In acetonitrile, the fast loss of the halide ligands results in the formation of [Mo2Cp2(μ-SMe)3(MeCN)2]+ species.
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Journal of Organometallic Chemistry, Elsevier, 2006, 691 (5), pp.898 - 906. 〈10.1016/j.jorganchem.2005.10.033〉
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Soumis le : mardi 5 septembre 2017 - 16:22:27
Dernière modification le : mercredi 11 avril 2018 - 10:56:01

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Christine Leroy, François Y. Pétillon, Kenneth W. Muir, Philippe Schollhammer, Jean Talarmin. Mixed μ-phosphido or μ-thiolato μ-halo-dimolybdenum(III) compounds [Mo2Cp2(μ-SMe)2(μ-X)(μ-Y)] (X=PPh2, Y=Cl; X=SCH3, Y=Br, I): Electrochemical and structural comparisons – The X-ray structure of [{Mo2Cp2Br(μ-O)(μ-SMe)2}2(μ-MoO4)]. Journal of Organometallic Chemistry, Elsevier, 2006, 691 (5), pp.898 - 906. 〈10.1016/j.jorganchem.2005.10.033〉. 〈hal-01582157〉

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