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Rates of Ligand Exchange around the Bis-Oxalato Complex [NpO2 (C2 O4 )2 ]3- Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi-Alkaline Conditions.
ChemPlusChem ( IF 3.0 ) Pub Date : 2018-03-02 , DOI: 10.1002/cplu.201800025 Corey D Pilgrim 1 , Harris E Mason 2 , Mavrik Zavarin 2 , William H Casey 1
ChemPlusChem ( IF 3.0 ) Pub Date : 2018-03-02 , DOI: 10.1002/cplu.201800025 Corey D Pilgrim 1 , Harris E Mason 2 , Mavrik Zavarin 2 , William H Casey 1
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The kinetics of ligand exchange between the free oxalate ion, C2 O4 2- , and the bis-oxalato NpV complex, [NpO2 (C2 O4 )2 ]3- , in aqueous solution are reported by using 13 C and 17 O NMR spectroscopy methods. Rates of exchange were measured in the pH regime of 6.5-9.0, at which speciation is shown to be suitably simple. Because the neptunium(V) complex is paramagnetic, the rates of ligand exchange were estimated by following the width of the 13 C and 17 O signals assigned to the free oxalate ion in solution and by applying the Swift-Connick method for measuring rates of exchange. A set of experiments were conducted in which pH and total oxalate concentration were varied, and the linear dependence of the rate on these parameters was demonstrated. Variable-temperature NMR spectroscopy was also performed to measure activation parameters of complexation. At pH<8.0, ΔH≠ =16.9 ±4.9 kJ mol-1 and ΔS≠ =-116.3 ±17.1 kJ mol-1 K-1 , whereas at pH>8.0 there is almost no dependence on temperature, which is interpreted to indicate that hydrolysis is coupled to ligand exchange under these conditions.
中文翻译：
在中性至半碱性条件下，使用多核NMR光谱法测量Bis-Oxalato络合物[NpO2（C2 O4）2] 3-周围的配体交换率。
使用13 C和17 O NMR光谱法报告了水溶液中游离草酸根离子C2 O4 2-和双草酸酯NpV络合物[NpO2（C2 O4）2] 3-之间的配体交换动力学。交换速率是在6.5-9.0的pH范围内测量的，在该pH范围内物种形成被证明是适当简单的。由于n（V）络合物是顺磁性的，因此可以通过跟踪分配给溶液中游离草酸根离子的13 C和17 O信号的宽度并应用Swift-Connick方法测量交换速率来估算配体交换速率。进行了一组实验，其中改变了pH和草酸总浓度，并且证明了速率对这些参数的线性依赖性。还进行了变温NMR光谱测量，以测量络合物的活化参数。在pH <8.0时，ΔH≠= 16.9±4.9 kJ mol-1和ΔS≠= -116.3±17.1 kJ mol-1 K-1，而在pH> 8.0时几乎不依赖于温度，这表明在这些条件下，水解与配体交换偶联。
更新日期：2018-03-02
中文翻译：
在中性至半碱性条件下，使用多核NMR光谱法测量Bis-Oxalato络合物[NpO2（C2 O4）2] 3-周围的配体交换率。
使用13 C和17 O NMR光谱法报告了水溶液中游离草酸根离子C2 O4 2-和双草酸酯NpV络合物[NpO2（C2 O4）2] 3-之间的配体交换动力学。交换速率是在6.5-9.0的pH范围内测量的，在该pH范围内物种形成被证明是适当简单的。由于n（V）络合物是顺磁性的，因此可以通过跟踪分配给溶液中游离草酸根离子的13 C和17 O信号的宽度并应用Swift-Connick方法测量交换速率来估算配体交换速率。进行了一组实验，其中改变了pH和草酸总浓度，并且证明了速率对这些参数的线性依赖性。还进行了变温NMR光谱测量，以测量络合物的活化参数。在pH <8.0时，ΔH≠= 16.9±4.9 kJ mol-1和ΔS≠= -116.3±17.1 kJ mol-1 K-1，而在pH> 8.0时几乎不依赖于温度，这表明在这些条件下，水解与配体交换偶联。
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