通过（17）O NMR 磁化转移研究强堿性溶液中铀酰(VI)氧与水之间氧交换的机理。

On the mechanism of oxygen exchange between uranyl(VI) oxygen and water in strongly alkaline solution as studied by (17)O NMR magnetization transfer.

机构信息

School of Chemical Science and Engineering, Department of Chemistry, Royal Institute of Technology (KTH), S-10044 Stockholm, Sweden.

出版信息

Inorg Chem. 2010 Jun 7;49(11):4928-33. doi: 10.1021/ic9025624.

DOI:10.1021/ic9025624

PMID:20450164

Abstract

The mechanism, rate constant, and activation parameters for the exchange between uranyl(VI) oxygen and water oxygen in tetramethyl ammonium hydroxide solution, TMA-OH, have been determined using (17)O NMR magnetization transfer technique. In the concentration range investigated, the predominant complex is UO(2)(OH)(4)(2-). The experimental rate equation, rate = k(ex)TMA-OH U(VI)(total) indicates that the exchange takes place via a binuclear complex or transition state with the stoichiometry [(UO(2)(OH)(4)(2-))(UO(2)(OH)(5)(3-)]. The rate-determining step most likely takes place between the axial "yl" oxygens and the equatorial hydroxides. The experimental Gibbs energy of activation, DeltaG(++) = 60.8 +/- 2.4 kJ/mol is in good agreement with the value, DeltaA(++) approximately DeltaG(++) = 52.3 +/- 5.4 kJ/mol, found by Buhl and Schreckenbach in a recent Car-Parrinello molecular dynamics study, indicating that their proposed "shuttle" mechanism may be applicable also on the proposed binuclear transition state.

摘要

使用 (17)O NMR 磁化转移技术确定了四甲基氢氧化铵溶液中铀酰(VI)氧与水氧之间的交换机制、速率常数和活化参数。在所研究的浓度范围内，主要的配合物是 UO(2)(OH)(4)(2-)。实验速率方程，速率=k(ex)TMA-OH U(VI)(总)表明，交换通过双核配合物或具有 [(UO(2)(OH)(4)(2-))(UO(2)(OH)(5)(3-)] 组成的过渡态发生。速率决定步骤最有可能发生在轴向“yl”氧原子和赤道羟基之间。实验活化吉布斯自由能，DeltaG(++)=60.8 +/- 2.4 kJ/mol，与 Buhl 和 Schreckenbach 在最近的 Car-Parrinello 分子动力学研究中发现的 DeltaA(++)约等于 DeltaG(++)=52.3 +/- 5.4 kJ/mol 非常吻合，表明他们提出的“穿梭”机制也可能适用于所提出的双核过渡态。