Exchange-Enhanced H-Abstraction Reactivity of High-Valent Nonheme Iron(IV)-Oxo from Coupled Cluster and Density Functional Theories
Exchange-Enhanced H-Abstraction Reactivity of High-Valent Nonheme Iron(IV)-Oxo from Coupled Cluster and Density Functional Theories
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DOI：
10.1021/jz100359h
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发表时间：
2010-05-20
影响因子：
5.7
通讯作者：
Shaik, Sason
中科院分区：
文献类型：
--
作者：
Chen, Hui;Lai, Wenzhen;Shaik, Sason
本文采用耦合团簇（RCCSD（T））和密度泛函理论（OFT）方法，对几种非血红素高价铁（IV）-羰基模型氧化剂在五重态和三重态下的甲烷夺氢（HAT）过程进行了计算研究.本工作通过RCCSD（T）计算证实了之前通过B3 LYP计算发现的五重态的交换增强HAT反应性。此外，我们在此基准29泛函对RCCSD（T）的结果。结果表明，B3 LYP方法给出了很好的三重态过渡态几何构型，而其五重态过渡态相对于RCCSD（T）来说是早的。TPSSh和M06 L在TS几何优化方面表现良好。然而，所有29个测试的DFT方法低估了五态HAT势垒，其中大多数也低估了三态HAT势垒。虽然B3 LYP、B3 LYP-D和TPSSh低估了五重态和三重态势垒，但它们的势垒及其五重态-三重态差异在一系列反应中与相应的RCCSD（T）量非常好地相关。
This letter reports a computational study of methane hydrogen abstraction (HAT) process by several nonheme high-valent iron(IV)-oxo model oxidants, in the quintet and triplet spin states, employing coupled-cluster (RCCSD(T))and density functional theory (OFT) methods. The exchange-enhanced HAT reactivity of the quintet state found previously by B3LYP calculations is confirmed in this work by means of the RCCSD(T) calculations. In addition, we benchmark herein 29 functionals against the RCCSD(T) results. It is found that B3LYP gives very good triplet-state transition state (TS) geometries, while its quintet-state TS is early relative to RCCSD(T). TPSSh and M06L perform well in TS geometry optimization. However, all 29 tested DFT methods underestimate the quintet-state HAT barriers, and most of them underestimate the triplet-state HAT barriers as well. Although B3LYP, B3LYP-D, and TPSSh underestimate both quintet-and triplet-state barriers, their barriers, and quintet-triplet differences thereof, in a series of reactions correlate extremely well with the corresponding RCCSD(T) quantities.