Electron Paramagnetic Resonance Signature of Tetragonal Low Spin Iron(V)-Nitrido and -Oxo Complexes Derived from the Electronic Structure Analysis of Heme and Non-Heme Archetypes
Electron Paramagnetic Resonance Signature of Tetragonal Low Spin Iron(V)-Nitrido and -Oxo Complexes Derived from the Electronic Structure Analysis of Heme and Non-Heme Archetypes
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DOI：
10.1021/jacs.8b11429
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发表时间：
2019-02-13
影响因子：
15
通讯作者：
Ye, Shengfa
中科院分区：
文献类型：
--
作者：
Chang, Hao-Ching;Mondal, Bhaskar;Ye, Shengfa
铁（V）-氮基和-氧代配合物已被提出作为各种化学转化的关键中间体。本文采用电子顺磁共振（EPR）和Fe-57穆斯堡尔谱结合基于波函数的完全活性空间自洽场（CASSCF）计算，对[Fe-V（N）（TPP）]（1，TPP 2- =四苯基卟啉）和[Fe-V（N）（cyclam-ac）]（+）（2，cyclam-ac = 1，4，8，11-四氮杂环十四烷-1-乙酰氧基）进行了详细的电子结构分析.这些发现与所有其他充分表征的真正的铁（V）-氮和-氧配合物[Fe-V（N）（MePy（2）tacn）]（PF 6）（2）进行了比较。（3，MePy（2）tacn =甲基-N '，N''-双（2-吡啶甲基）-1，4，7-三氮杂环壬烷），[Fe-V（N）{PhB（t-BuIm）（3）}]（+）（4，PhB（（t）BuIm）（3）（-）=苯基三（3-叔丁基咪唑-2-亚基）硼酸盐），和[Fe-V（O）（TAML）]（-）（5，TAML（4-）=四酰胺基大环配体）。我们的研究结果表明，配合物1是一个认证的铁（V）-氮化物物种和对比，其氧代同系物，化合物I，其中包含一个渡轮]单位与卟啉自由基相互作用。更重要的是，四价铁（V）-氮基和-氧代配合物1-3和5都具有接近双简并的S = 1/2基态。因此，类似的近轴EPR谱与g（平行）< g（垂直）
Iron(V)-nitrido and -oxo complexes have been proposed as key intermediates in a diverse array of chemical transformations. Herein we present a detailed electronic-structure analysis of [Fe-V(N)(TPP)] (1, TPP2- = tetraphenylporphyrinato), and [Fe-V(N)(cyclam-ac)](+) (2, cyclam-ac = 1,4,8,11-tetraazacyclotetradecane-1-acetato) using electron paramagnetic resonance (EPR) and Fe-57 Mossbauer spectroscopy coupled with wave function based complete active-space self-consistent field (CASSCF) calculations. The findings were compared with all other well-characterized genuine iron(V)-nitrido and -oxo complexes, [Fe-V(N)(MePy(2)tacn)](PF6)(2) (3, MePy(2)tacn = methyl-N',N ''-bis(2-picolyl)-1,4,7-triazacyclononane), [Fe-V(N){PhB(t-BuIm)(3)}](+) (4, PhB((t)BuIm)(3)(-) = phenyltris(3-tert-butylimidazol-2-ylidene)borate), and [Fe-V(O)(TAML)](-) (5, TAML(4-) = tetraamido macrocyclic ligand). Our results revealed that complex 1 is an authenticated iron(V)-nitrido species and contrasts with its oxo congener, compound I, which contains a ferry] unit interacting with a porphyrin radical. More importantly, tetragonal iron(V)-nitrido and-oxo complexes 1-3 and 5 all possess an orbitally nearly doubly degenerate S = 1/2 ground state. Consequently, analogous near-axial EPR spectra with g(parallel to) < g(perpendicular to)