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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >A kinetic and thermodynamic study of the unexpected comproportionation reaction between cis-[Os~(VIII)O_4(OH)_2] ~(2-) and trans-[Os~(VI)O_2(OH)_4] ~(2-) to form a postulated [Os~(VII)O_3(OH) _3]~(2-) complex anion
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A kinetic and thermodynamic study of the unexpected comproportionation reaction between cis-[Os~(VIII)O_4(OH)_2] ~(2-) and trans-[Os~(VI)O_2(OH)_4] ~(2-) to form a postulated [Os~(VII)O_3(OH) _3]~(2-) complex anion

机译：顺式-[Os〜（VIII）O_4（OH）_2]〜（2-）与反式-[Os〜（VI）O_2（OH）_4]〜（2-）意外复合反应的动力学和热力学研究形成假定的[Os〜（VII）O_3（OH）_3]〜（2-）络合物阴离子

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A kinetic study of [OsO_4] reduction by aliphatic alcohols (MeOH and EtOH) was performed in a 2.0 M NaOH matrix at 298.1 K. The rate model that best fitted the UV-VIS data supports a one-step, two electron reduction of Os~(VIII) (present as both the [Os~(VIII)O_4(OH)] ~- and cis-[Os~(VIII)O_4(OH)_2] ~(2-) species in a ratio of 0.34:0.66) to form the trans-[Os ~(VI)O_2(OH)_4]~(2-) species. The formed trans-[Os~(VI)O_2(OH)_4]~(2-) species subsequently reacts relatively rapidly with the cis-[Os~(VIII)O _4(OH)_2]~(2-) complex anion to form a postulated [Os~(VII)O_3(OH)_3]~(2-) species according to: cis-[Os~(VIII)O_4(OH)_2]~(2-) + trans-[Os~(VI)O_2(OH)_4]~(2-) 2[Os ~(VII)O_3(OH)_3]~(2-). The calculated forward, k_(+2), and reverse, k_(-2), reaction rate constants of this comproportionation reaction are 620.9 ± 14.6 M~(-1) s ~(-1) and 65.7 ± 1.2 M~(-1) s~(-1) respectively. Interestingly, it was found that the postulated [Os~(VII)O _3(OH)_3]~(2-) complex anion does not oxidize MeOH or EtOH. Furthermore, the reduction of Os~(VIII) with MeOH or EtOH is first order with respect to the aliphatic alcohol concentration. In order to corroborate the formation of the [Os~(VII)O_3(OH) _3]~(2-) species predicted with the rate model simulations, several Os~(VIII)/Os~(VI) mole fraction and mole ratio titrations were conducted in a 2.0 M NaOH matrix at 298.1 K under equilibrium conditions. These titrations confirmed that the cis-[Os~(VIII)O _4(OH)_2]~(2-) and trans-[Os~(VI)O _2(OH)_4]~(2-) species react in a 1:1 ratio with a calculated equilibrium constant, K_(COM), of 9.3 ± 0.4. The ratio of rate constants k_(+2) and k_(-2) agrees quantitatively with K_(COM), satisfying the principle of detailed balance. In addition, for the first time, the molar extinction coefficient spectrum of the postulated [Os~(VII)O_3(OH)_3]~(2-) complex anion is reported.
机译：在298.1 K的2.0 M NaOH基质中进行了脂肪族醇（MeOH和EtOH）还原[OsO_4]的动力学研究。最适合UV-VIS数据的速率模型支持一步一步，两个电子还原Os 〜（VIII）（以[Os〜（VIII）O_4（OH）]〜-和顺式[Os〜（VIII）O_4（OH）_2]〜（2-）的形式存在）形成反式[Os〜（VI）O_2（OH）_4]〜（2-）物种。形成的反式[[Os〜（VI）O_2（OH）_4]〜（2-）物种随后与顺式[[Os〜（VIII）O _4（OH）_2]〜（2-）配位阴离子快速反应形成假定的[Os〜（VII）O_3（OH）_3]〜（2-）物种，其依据是：顺式[Os〜（VIII）O_4（OH）_2]〜（2-）+反式-[Os〜 （VI）O_2（OH）_4]〜（2-）2 [Os〜（VII）O_3（OH）_3]〜（2-）。该补偿反应的正向k _（+ 2）和反向k _（-2）的反应速率常数分别为620.9±14.6 M〜（-1）s〜（-1）和65.7±1.2 M〜（- 1）分别为s〜（-1）。有趣的是，发现假定的[Os〜（VII）O_3（OH）_3]〜（2-）络合物阴离子不会氧化MeOH或EtOH。此外，相对于脂族醇浓度，用MeOH或EtOH还原Os-（VIII）是一阶的。为了证实通过速率模型模拟预测的[Os〜（VII）O_3（OH）_3]〜（2-）物种的形成，需要几个Os〜（VIII）/ Os〜（VI）摩尔分数和摩尔比在平衡条件下，在2.0M NaOH基质中于298.1 K进行滴定。这些滴定证实了顺-[Os〜（VIII）O _4（OH）_2]〜（2-）和反式-[Os〜（VI）O _2（OH）_4]〜（2-）物种在1：1的比例，计算出的平衡常数K_（COM）为9.3±0.4。速率常数k _（+ 2）和k _（-2）的比率与K_（COM）定量一致，满足详细平衡的原理。此外，首次报道了假定的[Os〜（VII）O_3（OH）_3]〜（2-）配位阴离子的摩尔消光系数谱。

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