Mechanistic Dichotomy in Proton-Coupled Electron-Transfer Reactions of Phenols with a Copper Superoxide Complex
作者:Wilson D. Bailey、Debanjan Dhar、Anna C. Cramblitt、William B. Tolman
DOI:10.1021/jacs.9b00466
日期:2019.4.3
H, Me, tBu are intermediate between the extremes). Thermodynamic analysis and comparisons to previous results for LCuOH, a different copper-oxygen intermediate with the same supporting ligand, and literature for other [CuO2]+ complexes reveal significant differences in proton-coupled electron-transfer mechanisms that have implications for understanding oxidation catalysis by copper-containing enzymes
[K(Krypt)][LCuO2] (Krypt = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, L = 双(芳基甲酰氨基)吡啶配体)与 2,2,6,6-四甲基哌啶-N-氢氧化物(TEMPOH)和对位取代酚 XArOH(X = 对位取代基 NO2、CF3、Cl、H、Me、tBu,研究了低温下的 OMe 或 NMe2)。与 TEMPOH 的反应通过二级动力学快速发生 (k = 35.4 ± 0.3 M-1 s-1) 以产生 TEMPO• 和 [LCuOOH]- 基于电子顺磁共振光谱,用质子处理后产生 H2O2 [NBu4][LCuOH] 与 H2O2 反应的独立制备(Keq = 0.022 ± 0.007 用于逆反应)。与 XArOH 的反应也遵循二级动力学,对 k 值随苯酚性质(哈米特σ 参数、OH 键解离自由能、p