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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >The reduction of tris-dithiolene complexes of molybdenum(VI) and tungsten(VI) by hydroxide ion:kinetics and mechanism
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The reduction of tris-dithiolene complexes of molybdenum(VI) and tungsten(VI) by hydroxide ion:kinetics and mechanism

机译：氢氧根离子还原钼（VI）和钨（VI）的tris-dithiolene配合物：动力学和机理

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The kinetic study of the spontaneous reduction of some neutral tris-dithiolene complexes [ML_3] of molybdenum(VI) and tungsten(VI),(L=S_2C_6H_4~2 ,S_2C_6H_3CH_3~2 and S_2C_2(CH_3)_2~(2-) ;M=Mo or W) by tetrabutylammonium hydroxide in tetrahydrofuran-water solutions demonstrates that OH~- is an effective reductant.Their reduction is fast,clean and quantitative.Depending upon both the molar ratio in which the reagents are mixed and the amount of water present,one- or two-electron reductions of these tris-dithiolene complexes were observed.If Bu_4NOH is present in low concentration or/and at high concentrations of water,the total transformation of the neutral M(VI) complex into the monoanionic M(v) complex is the only observed process.Stopped-flow kinetic data for this reaction are consistent with the rate law:-d[ML_3]/dt=d[ML_3]/dt=k[ML_3][Bu_4NOH].The proposed mechanism involves nucleophilic attack of OH~- to form a mono-anionic seven-coordinate intermediate [ML_3OH]~- ,which interacts with another molecule of [ML_3] to generate the monoanionic complex [ML_3]~- transfering the oxygen from coordinated OH~- to water.Hydrogen peroxide was identified as the reaction product.The molybdenum complexes are more difficult to reduce than their corresponding tungsten complexes,and the values of k obtained for the molybdenum and tungsten series of complexes increase as the ene-l,2-dithiolate ligand becomes more electron-withdrawing (S_2C_6H_4~(2-)>S_2C_6H_3CH_3~2>S_2C_2(CH_3)_2~(2-) ). This investigation constitutes the only well-established interaction between hydroxide ion and a tris(dithiolene) complex,and supports a highly covalent bonding interaction between the metal and the hydroxide ion that modulates electron transfer reactions within these complexes.
机译：钼（VI）和钨（VI），（L = S_2C_6H_4〜2，S_2C_6H_3CH_3〜2和S_2C_2（CH_3）_2〜（2-）的一些中性三-二硫代己烯络合物[ML_3]自发还原的动力学研究M = Mo或W）在四氢呋喃水溶液中的四丁基氢氧化铵溶液证明OH〜-是一种有效的还原剂，还原速度快，清洁且定量。取决于试剂混合的摩尔比和水的量目前，观察到这些tris-dithiolene配合物的单电子或两电子还原。如果Bu_4NOH以低浓度或/和高浓度存在于水中，则中性M（VI）配合物向单阴离子M（ v）复杂是唯一观察到的过程。该反应的停止流动力学数据与速率定律一致：-d [ML_3] / dt = d [ML_3] / dt = k [ML_3] [Bu_4NOH]。涉及OH〜-的亲核攻击，形成单阴离子七配位中间体[ML_3OH]〜-与另一分子[ML_3]生成单阴离子配合物[ML_3]〜-，将氧从配位的OH〜-转移到水中。过氧化氢被确定为反应产物。钼配合物比相应的钨配合物难于还原，随着烯-1,2-二硫代盐配体的吸电子量增加，钼和钨系列配合物的k值增加（S_2C_6H_4〜（2-）> S_2C_6H_3CH_3〜2> S_2C_2（CH_3）_2〜（ 2-））。该研究构成了氢氧根离子与三（二硫代戊二烯）配合物之间唯一公认的相互作用，并支持了金属与氢氧根离子之间的高度共价键相互作用，从而调节了这些配合物中的电子转移反应。

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