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A Switch from Mechanistic Competition Mediated by a Combination of Temperature and Concentration Effects in the Oxidation Reaction of [FeII (N4Py/TPA)](OTf)2.
Chemistry - A European Journal ( IF 4.3 ) Pub Date : 2018-07-19 , DOI: 10.1002/chem.201801028
Tzu-Hsien Tseng,Peter Ping-Yu Chen

The formation of [(N4Py)FeIV=O]2+ species was accomplished by the reaction of [FeII(N4Py)]2+ with 20 equivalents of tBuO2H (TBHP, 70 % in H2O). The temperature, [FeII(N4Py)]2+‐concentration and H2O‐concentration in anhydrous TBHP (5.5 m in decane) dependences of its yields and rates were analyzed to indicate that the proton migration from [(N4Py)FeII‐HOOtBu]2+ to [(N4Py)FeII‐OOHtBu]2+ is the rate‐determining step followed by rapid heterolytic O−O bond cleavage of FeII‐OOHtBu to FeIV=O complex. The formation of [(TPA)FeIV=O]2+ is thus revealed to be greatly enhanced by the similar oxidation of [FeII(TPA)]2+ (40 mm) with 10 equivalents of tBuO2H at −45 °C. These results demonstrate the heterolytic O−O bond cleavage of FeII‐alkylperoxo species to form FeIV=O originating from the direct reaction of iron(II) complexes/TBHP. The observation of concentration and temperature effects leads to the hypothesis that O−O bond homolysis is a kinetic control pathway and O−O bond heterolysis is a thermodynamic control pathway.

中文翻译:

在[FeII(N4Py / TPA)](OTf)2的氧化反应中,温度和浓度效应的组合介导了机械竞争的转变。

通过[Fe II(N4Py)] 2+与20当量的t BuO 2 H(TBHP,H 2 O中70%)的反应完成[(N4Py)Fe IV = O] 2+物种的形成。分析了温度,[Fe II(N4Py)] 2+浓度和H 2 O-浓度在无水TBHP(癸烷中为5.5  m)对产率和速率的依赖性,表明质子从[(N4Py)Fe II迁移出来。-HOO卜] 2+至[(N4Py)的Fe II -OO ħ卜] 2+是速率决定步骤,随后的Fe快速异裂O-O键裂解II -OO ħ卜成Fe IV = O复杂。因此显示[(TPA)Fe IV = O] 2+的形成通过[Fe II(TPA)] 2+(40 m m)在-10当量的t BuO 2 H的类似氧化而大大增强了。 45℃。这些结果证明了Fe II-烷基过氧物质的杂化O-O键裂解形成Fe IV= O源自铁(II)配合物/ TBHP的直接反应。浓度和温度效应的观察结果得出这样一个假设:O-O键均质分解是动力学控制途径,而O-O键杂质分解是热力学控制途径。
更新日期:2018-07-19
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