A High-Valent Iron-Oxo Corrolazine Activates C-H Bonds via Hydrogen-Atom Transfer
A High-Valent Iron-Oxo Corrolazine Activates C-H Bonds via Hydrogen-Atom Transfer
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DOI：
10.1021/ja3018658
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发表时间：
2012-05-02
影响因子：
15
通讯作者：
Goldberg, David P.
中科院分区：
文献类型：
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作者：
Cho, Kevin;Leeladee, Pannee;Goldberg, David P.
在各种条件下用O-原子转移氧化剂氧化Fe-Ⅲ配合物（TBP（8）Cz）Fe-III [TBP（8）Cz = octagis（4-tert-butylphenyl）corolazinate]得到反应性高价Fe（O）配合物（TBP（8）Cz（+中心点））Fe-IV（O）（2）。用XAS [d（Fe-O）= 1.64埃]表征了2的溶液态结构。该复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，这些反应通过氢原子转移（HAT）进行，log k与BDE（C-H）呈线性相关，氧杂蒽（Xn）底物的活化参数如下：Δ H-双匕首= 12.7 +/- 0.8 kcal mol（-1），Δ S-双匕首= -9 +/- 3 cal K-1 mol（-1），KIE = 5.7。通过降低反应温度有利于Xn的回弹羟基化与自由基二聚化。这些发现提供了深入了解的因素，控制化合物I血红素类似物的内在反应性。
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(+center dot))Fe-IV(O) (2). The solution state structure of 2 was characterized by XAS [d(Fe-O) = 1.64 angstrom]. 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: Delta H-double dagger = 12.7 +/- 0.8 kcal mol(-1), Delta S-double dagger = -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.