The Slowest Water Exchange at a Homoleptic Mononuclear Metal Center: Variable-Temperature and Variable-Pressure 17O NMR Study on [Ir(H2O)6]3+
The Slowest Water Exchange at a Homoleptic Mononuclear Metal Center: Variable-Temperature and Variable-Pressure 17O NMR Study on [Ir(H2O)6]3+
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同配单核金属中心最慢的水交换：[Ir(H2O)6]3 的变温变压 17O NMR 研究
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
A. Merbach
中科院分区：
文献类型：
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作者：
Antonio Cusanelli;U. Frey;D. Richens;A. Merbach
在几种酸度（0.5−5.0 m）下，六水和单羟基五水铱（III）的水交换速率常数和活化参数已通过 17O NMR 光谱确定为温度（358−406 K）和压力（0.1−210 MPa）的函数。非配位三氟甲磺酸盐(CF3SO3-)用作抗衡离子。观察到的速率常数的形式为 k = k1 + k2/[H+]，其中下标 1 和 2 分别指 [Ir(H2O)6]3+ 和 [Ir(H2O)5(OH)]2+ 上的交换路径。得到的动力学参数总结如下： k1298 = (1.1 ± 0.1) × 10-10 s-1, ΔH1⧧ = 130.5 ± 0.6 kJ mol-1, ΔS1⧧ = +2.1 ± 1.7 J K-1 mol-1, ΔV1⧧ = -5.7 ± 0.5 cm3 mol-1; k2298 = (1.4 ± 0.6) × 10-11 m s-1，ΔH2⧧ = 138.5 ± 4.5 kJ mol-1，ΔS2⧧ = +11.5 ± 11.6 J K-1 mol-1，ΔV2⧧ = -0.2 ± 0.8 cm3 mol-1。 k1298 获得的值对应于大约的停留时间。 300年。与 [Ir(H2O)6]3+ 第一次水解相关的 pKa298 和体积变化 ΔVa0 通过以下方法确定：
The rate constants and activation parameters for water exchange on hexaaqua and monohydroxy pentaaqua iridium(III) have been determined by 17O NMR spectroscopy as a function of temperature (358−406 K) and pressure (0.1−210 MPa) at several acidities (0.5−5.0 m). Noncoordinating trifluoromethanesulfonate (CF3SO3-) was used as the counterion. The observed rate constant was of the form k = k1 + k2/[H+], where the subscripts 1 and 2 refer to the exchange pathways on [Ir(H2O)6]3+ and [Ir(H2O)5(OH)]2+, respectively. The kinetic parameters obtained are summarized as follows: k1298 = (1.1 ± 0.1) × 10-10 s-1, ΔH1⧧ = 130.5 ± 0.6 kJ mol-1, ΔS1⧧ = +2.1 ± 1.7 J K-1 mol-1, and ΔV1⧧ = −5.7 ± 0.5 cm3 mol-1; k2298 = (1.4 ± 0.6) × 10-11 m s-1, ΔH2⧧ = 138.5 ± 4.5 kJ mol-1, ΔS2⧧ = +11.5 ± 11.6 J K-1 mol-1, and ΔV2⧧ = −0.2 ± 0.8 cm3 mol-1. The value obtained for k1298 corresponds to a residence time of ca. 300 years. The pKa298 and the volume change ΔVa0 associated with the first hydrolysis of [Ir(H2O)6]3+ were determined by ...