Electronic structure contributions to O–O bond cleavage reactions for Mn III -alkylperoxo complexes
Electronic structure contributions to O–O bond cleavage reactions for Mn III -alkylperoxo complexes
复制标题
电子结构对 Mn III -烷基过氧配合物 O−O 键断裂反应的贡献
DOI：
10.1039/d3dt01672b
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发表时间：
2023
影响因子：
4
通讯作者：
Jackson, Timothy A.
中科院分区：
文献类型：
--
作者：
Brunclik, Samuel A.;Opalade, Adedamola A.;Jackson, Timothy A.
活化过氧化氢的合成锰催化剂进行各种烃氧化反应。这些催化剂最常提出的机理涉及生成锰（III）-过氧化氢中间体，该中间体通过异裂O-O键裂解衰变以生成引发底物氧化的Mn（V）-氧代物质。由于缺乏定义明确的MnIII-氢过氧络合物，MnIII-烷基过氧络合物经常被用来了解影响O-O裂解反应的因素。在此，我们研究了MnIII-烷基过氧配合物[MnIII（OOtBu）（6 Medpaq）]+和[MnIII（OOtBu）（N4S）]+的衰变途径，它们具有不同的配位环境（分别为N5−和N4S−）。通过使用密度泛函理论（DFT）的计算和与已发表的实验数据的比较，我们能够合理化这些复合物的衰变途径的差异。对于[MnIII（OOtBu）（N4S）]+系统，O-O均裂通过两态机制进行，该机制涉及从五重态反应物到三重态的交叉。高能量的单重态阻碍了该复合物的O-O异裂。相比之下，虽然五重态-三重态交叉对[MnIII（OOtBu）（6 Medpaq）]+是不利的，但相对低能量的单一状态解释了该复合物的O-O均裂和异裂产物的观察。衰变途径的这些差异的起源与锰III-烷基过氧络合物的电子结构的变化有关。
Synthetic manganese catalysts that activate hydrogen peroxide perform a variety of hydrocarbon oxidation reactions. The most commonly proposed mechanism for these catalysts involves the generation of a manganese(III)-hydroperoxo intermediate that decays via heterolytic O–O bond cleavage to generate a Mn(V)-oxo species that initiates substrate oxidation. Due to the paucity of well-defined MnIII-hydroperoxo complexes, MnIII-alkylperoxo complexes are often employed to understand the factors that affect the O–O cleavage reaction. Herein, we examine the decay pathways of the MnIII-alkylperoxo complexes [MnIII(OOtBu)(6Medpaq)]+ and [MnIII(OOtBu)(N4S)]+, which have distinct coordination environments (N5− and N4S−, respectively). Through the use of density functional theory (DFT) calculations and comparisons with published experimental data, we are able to rationalize the differences in the decay pathways of these complexes. For the [MnIII(OOtBu)(N4S)]+ system, O–O homolysis proceeds via a two-state mechanism that involves a crossing from the quintet reactant to a triplet state. A high energy singlet state discourages O–O heterolysis for this complex. In contrast, while quintet–triplet crossing is unfavorable for [MnIII(OOtBu)(6Medpaq)]+, a relatively low-energy single state accounts for the observation of both O–O homolysis and heterolysis products for this complex. The origins of these differences in decay pathways are linked to variations in the electronic structures of the MnIII-alkylperoxo complexes.