Theory Revealing Unusual Non-Rebound Mechanisms Responsible for the Distinct Reactivities of O═MnIV═O and [HO–MnIV–OH]2+ in C–H Bond Activation

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• 作者：Dibyendu Mallick ; Sason Shaik
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：May 6, 2016
• 年：2016
• 卷：6
• 期：5
• 页码：2877-2888
• 全文大小：772K
• 年卷期：0
• ISSN：2155-5435

文摘

This article uses theory to address the origins of the reactivity differences between Mn^IV═O and Mn^IV–OH complexes, having identical ligand spheres and metal oxidation states, toward 9,10-dihydroanthracene (DHA) under different pH conditions. Theory discovers different non-rebound mechanisms leading to unique products for the two complexes. One of these is a novel mechanism that operates under basic conditions and that rationalizes the formation of anthraquinone through an anthracene radical anion intermediate. In addition, the calculations reveal a rich mechanistic scheme having blended hydrogen atom transfer and proton-coupled electron transfer (HAT/PCET) with both proton transfer/electron transfer (PT/ET) and electron transfer/proton transfer (ET/PT) characters. The distinct nature of the transition states, such as PT/ET and ET/PT, for the second H-abstraction reactions from the substrate radical by the Mn^IV═O and Mn^IV–OH complexes accounts for the observed product distributions for these two species. The formation of an anthracene radical anion, and its participation in a unique non-rebound mechanism, is a testable prediction.