Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species
Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species
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DOI：
10.1073/pnas.0409640102
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发表时间：
2005-04-12
影响因子：
11.1
通讯作者：
Que, L
中科院分区：
文献类型：
--
作者：
Shan, XP;Que, L
[Fe-2（μ-OH）（2）]的反应（6-Me-3-TPA）（2）]（2+）（1）[6-Me-3-TPA，Tris（6-甲基-2-吡啶基甲基）胺]与O-2在CH 2Cl 2中于-80 ℃反应，得到两个新的中间体2和3，在形成之前表征的[Fe-2（O）（O-2）（6-Me-3-TPA）（2）]（2+）（4）之前，其允许氧化反应一次一个电子转移步骤地被监测。拉曼证据指定2和3作为一个二铁superoxo物种和二铁过氧物种，分别。中间体2在1，310 cm（-1）处显示其nu（O-O），具有-71-cm（-1）O-18同位素位移。在混合同位素拉曼实验中，2的（OO）-O-16-O-18同位素异构体的双峰模式强烈表明2的超氧配体是端对结合的。与4的结合过氧化物不同，2的结合超氧化物很容易被2，4-二叔丁基苯酚通过质子耦合电子转移机制还原，强调金属-superoxo物种可能在金属酶的氧活化机制中充当氧化剂。中间体2和3的发现使我们能够剖析在二铁中心导致其活化底物氧化的二氧结合的初始步骤。
The reaction of [Fe-2(mu-OH)(2)(6-Me-3-TPA)(2)](2+) (1) [6-Me-3-TPA, Tris(6-methyl-2-pyridylmethyl)amine] with O-2 in CH2Cl2 at -80 degrees C gives rise to two new intermediates, 2 and 3, before the formation of previously characterized [Fe-2(O)(O-2)(6-Me-3-TPA)(2)](2+) (4) that allow the oxygenation reaction to be monitored one electron-transfer step at a time. Raman evidence assigns 2 and 3 as a diiron-superoxo species and a diiron-peroxo species, respectively. Intermediate 2 exhibits its nu(O-O) at 1,310 cm(-1) with a -71-cm(-1) O-18 isotope shift. A doublet peak pattern for the (OO)-O-16-O-18 isotopomer of 2 in mixed-isotope Raman experiments strongly suggests that the superoxide ligand of 2 is bound end-on. This first example of a nonheme iron-superoxo intermediate exhibits the highest frequency nu(O-O) yet observed for a biomimetic metal-dioxygen adduct. The bound superoxide of 2, unlike the bound peroxide of 4, is readily reduced by 2,4-di-tert-butylphenol via a proton-coupled electron-transfer mechanism, emphasizing that metal-superoxo species may serve as oxidants in oxygen activation mechanisms of metalloenzymes. The discovery of intermediates 2 and 3 allows us to dissect the initial steps of dioxygen binding at a diiron center leading to its activation for substrate oxidation.