Redox potential and C-H bond cleaving properties of a nonheme Fe(IV)=O complex in aqueous solution.
Redox potential and C-H bond cleaving properties of a nonheme Fe(IV)=O complex in aqueous solution.
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水溶液中非血红素 Fe(IV)=O 络合物的氧化还原电位和 C-H 键裂解特性。
DOI：
10.1021/ja909923w
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发表时间：
2010
影响因子：
15
通讯作者：
QueJr,Lawrence
中科院分区：
文献类型：
--
作者：
Wang,Dong;Zhang,Mo;Bühlmann,Philippe;QueJr,Lawrence
高价铁−氧中间体已被确定为许多非血红素酶催化循环中的关键氧化剂。在迄今为止表征的大量合成FeIV-O配合物中，[FeIV（O）（N4 Py）]2+（1）表现出热力学稳定性的独特组合，允许通过X射线晶体学对其结构进行表征，并且氧化反应性足以像在环己烷中一样强地裂解C-H键（DC-H = 99.3 kcal mol−1）。然而，它的氧化还原性质还没有很好地理解。在这项工作中，质子对1的氧化还原性能的影响进行了电化学研究，在非水溶液和水溶液。虽然1在CH 3CN中的循环伏安法由于几个化学和氧化还原过程的耦合而变得复杂，但FeIV/III电对在水溶液中是可逆的，E1/2= +0.41 V（pH 4时相对于SCE），并且涉及一个电子和一个质子的转移以产生FeIII−OH物质。这实际上是第一个例子可逆电化学观察到这个家庭的nonheme oxoiron（IV）配合物。在H2O中研究了C-H键被1氧化的反应，发现反应速率取决于C-H键的强度，而不是溶剂。此外，我们的电化学结果允许从1衍生的FeIII−OH单元计算出78（2）kcal mol− 1的DO− H值。有趣的是，虽然这个DO− H值比[FeIV（O）（TMP）]（TMP =四均三甲苯基卟啉）、[RuIV（O）（bpy）2（py）]2+（bpy =联吡啶，py =吡啶）和叔丁基过氧自由基等氧化剂的DO− H值低6−11 kcal mol− 1，但二氢蒽被1氧化的速率与这些其他氧化剂相当。这种比较表明，非血红素N4 Py配体环境赋予了一个动力学优势，比其他增强C-H键裂解能力的1。
High-valent iron−oxo intermediates have been identified as the key oxidants in the catalytic cycles of many nonheme enzymes. Among the large number of synthetic FeIVO complexes characterized to date, [FeIV(O)(N4Py)]2+(1) exhibits the unique combination of thermodynamic stability, allowing its structural characterization by X-ray crystallography, and oxidative reactivity sufficient to cleave C−H bonds as strong as those in cyclohexane (DC−H= 99.3 kcal mol−1). However, its redox properties are not yet well understood. In this work, the effect of protons on the redox properties of1has been investigated electrochemically in nonaqueous and aqueous solutions. While the cyclic voltammetry of1in CH3CN is complicated by coupling of several chemical and redox processes, the FeIV/IIIcouple is reversible in aqueous solution withE1/2= +0.41 V versus SCE at pH 4 and involves the transfer of one electron and one proton to give the FeIII−OH species. This is in fact the first example of reversible electrochemistry to be observed for this family of nonheme oxoiron (IV) complexes. C−H bond oxidations by1have been studied in H2O and found to have reaction rates that depend on the C−H bond strength but not on the solvent. Furthermore, our electrochemical results have allowed a DO−Hvalue of 78(2) kcal mol−1to be calculated for the FeIII−OH unit derived from1. Interestingly, although this DO−Hvalue is 6−11 kcal mol−1lower than those corresponding to oxidants such as [FeIV(O)(TMP)] (TMP = tetramesitylporphinate), [RuIV(O)(bpy)2(py)]2+(bpy = bipyridine, py = pyridine), and thetert-butylperoxyl radical, the oxidation of dihydroanthracene by1occurs at a rate comparable to rates for these other oxidants. This comparison suggests that the nonheme N4Py ligand environment confers a kinetic advantage over the others that enhances the C−H bond cleavage ability of1.
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影响因子：
16.6
作者：
Klinker, Eric J.;Shaik, Sason;Hirao, Hajime;Que, Lawrence, Jr.
通讯作者：
Que, Lawrence, Jr.
DOI：
10.1002/anie.199515121
发表时间：
1995-07-31
期刊：
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH
影响因子：
--
作者：
LUBBEN, M;MEETSMA, A;QUE, L
通讯作者：
QUE, L
影响因子：
16.6
作者：
Klinker, EJ;Kaizer, J;Que, L
通讯作者：
Que, L
影响因子：
15
作者：
Riggs-Gelasco, PJ;Price, JC;Krebs, C
通讯作者：
Krebs, C
影响因子：
16.6
作者：
Hirai, Yuichirou;Kojima, Takahiko;Fukuzumi, Shunichi
通讯作者：
Fukuzumi, Shunichi