What factors tune the chemical equilibrium between metal-iodosylarene oxidants and high-valent metal-oxo ones?
What factors tune the chemical equilibrium between metal-iodosylarene oxidants and high-valent metal-oxo ones?
复制标题
哪些因素调节金属碘代芳烃氧化剂和高价金属氧氧化剂之间的化学平衡？
DOI：
10.1039/c8cp06117c
复制
发表时间：
2019
影响因子：
3.3
通讯作者：
Yong Wang
中科院分区：
文献类型：
--
作者：
Lili Yang;Fang Wang;Jiali Gao;Yong Wang
金属碘代芳烃配合物（1）和高价金属氧代配合物（2）是氧化反应中的两个关键中间体。已经进行了大量的实验努力，探索这两个难以捉摸的氧化剂的结构-功能关系，然而，有争议的建议，基于这些实验结果和缺失的机制细节要求的相互作用的理论方法与这些现有的实验，特别是调整两个氧化剂1和2之间的化学平衡的因素。在此，密度泛函计算已经进行，结果表明，三氟甲磺酸根抗衡离子（OTf）的效果是不是众所周知的轴向配体效应。相反，它通过一种新的卤键相互作用起作用。这种卤键相互作用不仅增加了可逆反应的反应速率，而且与非卤键的情况相比，它还使平衡点向金属-碘代芳烃氧化剂的方向移动。实验观察到的物质与S = 5/2的信号被确定为OTf-卤素键合铁（iii）-碘酰苯物种。研究了碘代芳烃的取代基效应，结果表明，氟取代越多，反应势垒越高，氧化体系中金属-碘代芳烃氧化剂的用量越少。本文的理论研究将有助于仿生氧化领域的研究人员对金属碘代芳烃化学有更深刻的认识，并设计出更合理的催化剂。
Metal-iodosylarene complexes (1) and high-valent metal-oxo complexes (2) are two key reactive intermediates in oxygenation reactions. Extensive experimental efforts have been carried out to explore the structure-function relatioship of these two elusive oxidants, however, controversial proposals based on these experimental results and the missing mechanistic details call for the interplay of a theoretical approach with these existing experimental ones, especially for the factors that tune the chemical equilibrium between the two oxidants 1 and 2. Herein, density functional calculations have been performed and the results demonstrated that the effect of triflate counterions (OTf) is not the well known axial ligand effect. Instead, it works via a novel halogen bond interaction. This halogen bond interaction not only increases the reaction rate of reversible reactions, but it also makes the equilibrium point shift to the direction of the metal-iodosylarene oxidant, compared with the non-halogen bond case. An experimentally observed species with a signal of S = 5/2 was identified as an OTf-halogen-bonding iron(iii)-iodosylbenzene species. The substituent effects of iodoarenes were also studied and the results show that the more fluorine substitution, the higher the reaction barrier and the smaller the amount of metal-iodosylarene oxidant in the oxidation system. Our theoretical study will help researchers in the biomimetic oxidation field have a more profound knowledge on metal-iodosylarene chemistry and design more rational catalysts.