Lam William W Y, Yiu Shek-Man, Yiu Douglas T Y, Lau Tai-Chu, Yip Wing-Ping, Che Chi-Ming
Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong, China.
Inorg Chem. 2003 Dec 1;42(24):8011-8. doi: 10.1021/ic034782j.
The oxidations of a series of 21 alkylaromatic compounds by trans-Ru(VI)(L)(O)(2) (L = 1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) have been studied in CH(3)CN. Toluene is oxidized to benzaldehyde and a small amount of benzyl alcohol. 9,10-Dihydroanthracene is oxidized to anthracene and anthraquinone. Other substrates give oxygenated products. The kinetics of the reactions were monitored by UV-vis spectrophotometry, and the rate law is: -d[Ru(VI)]/dt = k(2)[Ru(VI)][ArCH(3)]. The kinetic isotope effects for the oxidation of toluene/d(8)-toluene and fluorene/d(10)-fluorene are 15 and 10.5, respectively. A plot of Delta H(++) versus Delta S(++) is linear, suggesting a common mechanism for all the substrates. In the oxidation of para-substituted toluenes, a linear correlation between log k(2) and sigma(0) values is observed, consistent with a benzyl radical intermediate. A linear correlation between Delta G(++) and Delta H(0) (the difference between the strength of the bond being broken and that being formed in a H-atom transfer step) is also found, which strongly supports a hydrogen atom transfer mechanism for the oxidation of these substrates by trans-Ru(VI)(L)(O)(2). The slope of (0.61 +/- 0.06) is in reasonable agreement with the theoretical slope of 0.5 predicted by Marcus theory.
在乙腈中研究了一系列21种烷基芳烃化合物被反式-[Ru(VI)(L)(O)₂]²⁺(L = 1,12-二甲基-3,4:9,10-二苯并-1,12-二氮杂-5,8-二氧杂环十五烷)氧化的反应。甲苯被氧化为苯甲醛和少量苯甲醇。9,10-二氢蒽被氧化为蒽和蒽醌。其他底物生成氧化产物。通过紫外-可见分光光度法监测反应动力学,速率方程为:-d[Ru(VI)]/dt = k₂[Ru(VI)][ArCH₃]。甲苯/d₈-甲苯和芴/d₁₀-芴氧化反应的动力学同位素效应分别为15和10.5。ΔH⁺⁺对ΔS⁺⁺的作图呈线性,表明所有底物的反应机理相同。在对二甲苯取代的甲苯氧化反应中,观察到log k₂与σ₀值之间存在线性相关性,这与苄基自由基中间体一致。还发现ΔG⁺⁺与ΔH₀(氢原子转移步骤中被断裂键和形成键的强度之差)之间存在线性相关性,这有力地支持了反式-[Ru(VI)(L)(O)₂]²⁺氧化这些底物的氢原子转移机理。其斜率为(0.61 ± 0.06),与Marcus理论预测的理论斜率0.5合理相符。