Yang Yixuan, Stanbury David M
Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States.
Inorg Chem. 2024 Jan 22;63(3):1625-1632. doi: 10.1021/acs.inorgchem.3c03796. Epub 2024 Jan 5.
The aqueous reaction of [IrCl] with CHSO is biphasic and yields a 1:1 mixture of [IrCl] and [IrCl(HO)] and CHSOCl in the initial rapid phase. The next slow phase corresponds to the hydrolysis of CHSOCl to yield CHSO and Cl. The initial phase shows kinetic inhibition by [IrCl] that can be minimized by the addition of the radical scavenger propiolic acid. A detailed analysis of the kinetics indicates a mechanism with reversible outer-sphere electron transfer from CHSO to [IrCl] as the first step, followed by the irreversible inner-sphere oxidation of CHSO by [IrCl] to yield [IrCl(HO)] and CHSOCl. Analysis of the inhibition by [IrCl] and the kinetic effects of propiolic acid enable the determination of the equilibrium constant for the first electron-transfer step. This equilibrium constant then yields ° (CHSO/CHSO) = 1.01 V vs NHE at 25 °C. This is the first report of a standard potential for an alkanesulfonyl radical.
[IrCl] 与CHSO的水相反应是两相的，在初始快速阶段生成[IrCl] 和 [IrCl(HO)] 以及CHSOCl的1:1混合物。接下来的缓慢阶段对应于CHSOCl水解生成CHSO和Cl。初始阶段显示出[IrCl] 的动力学抑制作用，通过添加自由基清除剂丙炔酸可将其降至最低。对动力学的详细分析表明，第一步是CHSO向[IrCl] 进行可逆的外层电子转移，随后是[IrCl] 对CHSO进行不可逆的内层氧化，生成[IrCl(HO)] 和CHSOCl。对[IrCl] 的抑制作用以及丙炔酸的动力学效应的分析能够确定第一个电子转移步骤的平衡常数。该平衡常数进而得出25℃时相对于标准氢电极（NHE）的 ° (CHSO/CHSO) = 1.01 V。这是关于烷基亚磺酰基自由基标准电位的首次报道。
