Characterization and Reactivity of an Incredibly Reactive Intermediate in the Protonation Reaction of Dioxo-Manganese(V) Porphyrin with Acid
Characterization and Reactivity of an Incredibly Reactive Intermediate in the Protonation Reaction of Dioxo-Manganese(V) Porphyrin with Acid
复制标题
二氧代锰 (V) 卟啉与酸的质子化反应中极其活跃的中间体的表征和反应活性
DOI：
10.1021/acscatal.2c06122
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发表时间：
2023
期刊：
影响因子：
12.9
通讯作者：
and Hiroshi Fujii
中科院分区：
文献类型：
--
作者：
Yuri Katogi;Ayano Okamoto;Masahiko Hada;and Hiroshi Fujii
锰（V）O（P）是一种新型的卟啉配合物，它具有很高的反应活性，是一种新型的卟啉配合物。为了表征Mn（V）O（P），我们研究了一种新的策略，其中Mn（V）O（P）是通过在低温下使用快速混合停流技术用各种酸对二氧代锰（V）四均三甲苯基卟啉配合物（1）的氧代配体进行质子化来生成的。在−40 °C下，将含有100当量四正丁基氢氧化铵（TBAOH）的1溶液与25-50当量三氟乙酸（TFA-H）快速混合，生成新的中间体（2），其吸收峰位于423、516和643 nm处。当将100当量的TFA-H与含有100当量TBAOH的1的溶液混合时，在混合后立即观察到另一种新的中间体（3），其在404、418和660 nm处具有吸收峰。2和3分别与过量TBAOH和三（对溴苯基）胺反应确定了Mn（V）的氧化态，2和3可由其它酸生成，3可由2与TFA-H反应生成。3与不同底物反应的动力学分析表明，3可以催化环氧化、夺氢和羟基化反应，其反应速率比相应的可咯和corrolazine配合物快得多。3的反应速率也比氧代铁（IV）卟啉π-阳离子自由基络合物高103-105倍，被称为最强大的金属-氧代卟啉络合物。这些结果表明，2和3是最可靠的候选人，为长期寻找的Mn（V）O（P）具有氢氧化物和水的轴向配体分别。
A monooxo-manganese(V) porphyrin complex, Mn(V)O(P), has been proposed as a reactive intermediate in the catalytic reactions, but Mn(V)O(P) is still a long-sought intermediate probably because of its high reactivity. To characterize Mn(V)O(P), we examined a new strategy, where Mn(V)O(P) is generated by the protonation of the oxo ligand of dioxo-manganese(V) tetramesitylporphyrin complex (1) with various acids by using a rapid-mixing stopped-flow technique at low temperatures. Rapid mixing of the solution of1containing 100 equiv oftetra-n-butylammonium hydroxide (TBAOH) with 25–50 equiv of trifluoroacetic acid (TFA-H) at −40 °C generates a new intermediate (2), having the absorption peaks at 423, 516, and 643 nm. When 100 equiv of TFA-H is mixed with the solution of1containing 100 equiv of TBAOH, another new intermediate (3), having absorption peaks at 404, 418, and 660 nm, is observed immediately after mixing. The Mn(V) oxidation states of2and3are confirmed by the reaction with excess TBAOH and tris(p-bromophenyl)amine, respectively.2and3can be generated by other acids.3can be produced from the reaction of2with TFA-H. The kinetic analysis of the reaction of3with various substrates shows that3can catalyze epoxidation, hydrogen abstraction, and hydroxylation reactions with incomparably faster reaction rates than the corresponding corrole and corrolazine complexes. The reaction rates of3are also 103–105-fold higher than those of oxoiron(IV) porphyrin π-cation radical complexes, known as the most powerful metal-oxo porphyrin complexes.2is less reactive than3. These results indicate that2and3are the most reliable candidate for the long-sought Mn(V)O(P) having hydroxide and aqua axial ligands, respectively.