Generation and Aerobic Oxidative Catalysis of a Cu(II) Superoxo Complex Supported by a Redox-Active Ligand
Generation and Aerobic Oxidative Catalysis of a Cu(II) Superoxo Complex Supported by a Redox-Active Ligand
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DOI：
10.1021/jacs.2c04630
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发表时间：
2022-08-17
影响因子：
15
通讯作者：
Anderson, John S.
中科院分区：
文献类型：
--
作者：
Czaikowski, Maia E.;McNeece, Andrew J.;Anderson, John S.
铜体系在生物和合成化学的有氧氧化催化中具有重要的作用。金属配体协同性是这两个领域的共同主题，例如半乳糖氧化酶和醇氧化中的氨氧基自由基。这激发了对铜的有氧化学的研究，特别是对作为关键催化中间体的铜-superoxo物种的分离和研究。虽然已经报道了模拟生物相关Cu（II）超氧中间体的络合物的几个实例，但它们通常不是合格的好氧催化剂。在这里，我们报告了一个新的铜配合物的氧化还原活性配体（DHP）-D-tBu，Tol（2，5-双（（2-叔丁基亚肼基）（对甲苯基）甲基）-吡咯），激活O-2通过配体为基础的电子转移产生催化活性的Cu（II）-superoxo配合物。使用紫外（UV）-可见光谱，拉曼同位素标记的研究，和铜扩展X-射线吸收精细结构（EXAFS）分析的表征证实了终端上kappa 1 superoxo复杂的分配。该Cu-O-2络合物参与一系列与包括醇和醛的底物的有氧催化氧化。这些结果表明，仿生铜系统不仅可以模拟重要的生物无机中间体，而且还可以介导和提供有氧氧化转化的机理见解。
Cu systems feature prominently in aerobic oxidative catalysis in both biology and synthetic chemistry. Metal ligand cooperativity is a common theme in both areas as exemplified by galactose oxidase and by aminoxyl radicals in alcohol oxidations. This has motivated investigations into the aerobic chemistry of Cu and specifically the isolation and study of Cu-superoxo species that are invoked as key catalytic intermediates. While several examples of complexes that model biologically relevant Cu(II) superoxo intermediates have been reported, they are not typically competent aerobic catalysts. Here, we report a new Cu complex of the redox-active ligand (DHP)-D-tBu,Tol (2,5-bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole) that activates O-2 to generate a catalytically active Cu(II)-superoxo complex via ligand-based electron transfer. Characterization using ultraviolet (UV)-visible spectroscopy, Raman isotope labeling studies, and Cu extended X-ray absorption fine structure (EXAFS) analysis confirms the assignment of an end-on kappa 1 superoxo complex. This Cu-O-2 complex engages in a range of aerobic catalytic oxidations with substrates including alcohols and aldehydes. These results demonstrate that bioinspired Cu systems can not only model important bioinorganic intermediates but can also mediate and provide mechanistic insight into aerobic oxidative transformations.