Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
J Am Chem Soc. 2012 May 2;134(17):7392-9. doi: 10.1021/ja3018658. Epub 2012 Apr 24.
Oxidation of the Fe(III) complex (TBP(8)Cz)Fe(III) [TBP(8)Cz = octakis(4-tert-butylphenyl)corrolazinate] with O-atom transfer oxidants under a variety of conditions gives the reactive high-valent Fe(O) complex (TBP(8)Cz(+•))Fe(IV)(O) (2). The solution state structure of 2 was characterized by XAS [d(Fe-O) = 1.64 Å]. This complex is competent to oxidize a range of C-H substrates. Product analyses and kinetic data show that these reactions occur via rate-determining hydrogen-atom transfer (HAT), with a linear correlation for log k versus BDE(C-H), and the following activation parameters for xanthene (Xn) substrate: ΔH(++) = 12.7 ± 0.8 kcal mol(-1), ΔS(++) = -9 ± 3 cal K(-1) mol(-1), and KIE = 5.7. Rebound hydroxylation versus radical dimerization for Xn is favored by lowering the reaction temperature. These findings provide insights into the factors that control the intrinsic reactivity of Compound I heme analogues.
用 O-原子转移氧化剂在各种条件下氧化 Fe(III)配合物（TBP(8)Cz)Fe(III）[TBP(8)Cz = 八(4-叔丁基苯基)corrolazinate]，得到反应性高价态 Fe(O)配合物（TBP(8)Cz(+•))Fe(IV)(O)（2）。2 的溶液状态结构通过 XAS [d(Fe-O) = 1.64 Å]进行了表征。该配合物能够氧化一系列 C-H 底物。产物分析和动力学数据表明，这些反应通过决定速率的氢原子转移（HAT）发生，对于 xanthene（Xn）底物，log k 与 BDE(C-H)之间存在线性关系，并且具有以下活化参数：ΔH(++) = 12.7 ± 0.8 kcal mol(-1)，ΔS(++) = -9 ± 3 cal K(-1) mol(-1)，和 KIE = 5.7。降低反应温度有利于 Xn 的反弹羟基化与自由基二聚化的竞争。这些发现为控制化合物 I 血红素类似物的固有反应性的因素提供了深入了解。
