The reaction of the dinuclear peroxotungstate, [(n-C4H9)4N]2[{WO(O2)2}2(ﾎｼ-O)] (2) with H2O2 gives the novel ﾎｼ-ﾎｷ1:ﾎｷ1-peroxo-bridging dinuclear tungsten species [(n-C4H9)4N]2[{WO(O2)2}2(ﾎｼ-O2)] (1) which has been characterized by X-ray crystallog., elemental anal., IR, Raman, UV-vis and 183W NMR. Only 1 is active for the epoxidn. of cyclic, internal, and terminal olefins, whereas 2 is inactive for each. The low XSO (XSO = (nucleophilic oxidn.)/(total oxidn.)) value of 1 (0.18 ﾂｱ 0.02) in comparison with that of 2 (0.39 ﾂｱ 0.01) for the stoichiometric oxidn. of thianthrene 5-oxide, which is a mechanistic probe for detg. the electronic character of an oxidant, reveals that 1 is more electrophilic than 2. On the basis of the kinetic and spectroscopic results the catalytic epoxidn. proceeds by the reaction of 1 with an olefin to form 2 and the corresponding epoxide followed by the regeneration of 1 by the reaction of 2 with H2O2. [on SciFinder(R)]
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