结构表征 μ-1,2-Peroxo/Superoxo Dicopper(II) 对,Journal of the American Chemical Society

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结构表征 μ-1,2-Peroxo/Superoxo Dicopper(II) 对
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2021-06-30 , DOI: 10.1021/jacs.1c04316
Alexander Brinkmeier ₁ , Roland A Schulz ₁ , Moritz Buchhorn ₂ , Can-Jerome Spyra ₁ , Sebastian Dechert ₁ , Serhiy Demeshko ₁ , Vera Krewald ₂ , Franc Meyer _{1,

3}

Affiliation

铜的超氧配合物是几种 O ₂活化含铜金属酶以及其他铜介导的氧化和氧化反应的主要加合物。然而，由于其固有的高反应性，Cu _x (O ₂^•– ) 物种的分离具有挑战性。近期工作 ( J. Am. Chem. Soc. 2017 , 139 , 9831; 2019 , 141, 12682) 建立了双铜 (II) 超氧配合物的 H 原子提取反应性的基本热化学数据，但迄今为止缺乏这些重要中间体的结构表征。在这里，我们报告了超氧双铜 (II) 物种 ( 3 )的首次晶体结构测定及其 1e ^–还原过氧同系物 ( 2 ; 一种罕见的顺式-μ-1,2-过氧双铜 (II) 复合物) . 的相互转换2和3发生在低电势（-0.58相对于Fc / Fc的⁺），并且是可逆的化学和电化学。度量参数的比较 ( d (O–O) = 1.441(2) Å for 2vs 1.329(7) Å for 3 ) 和光谱特征 (ν̃( ¹⁶ O– ¹⁶ O) = 793 cm ^–1 for 2 vs 1073 cm ^–1 for 3 ) 反映氧化还原过程发生在桥接 O ₂衍生单元。根据磁性和 EPR 数据，Cu ^II –O ₂^•– –Cu ^II复合物具有S = 1/2 自旋基态，与密度泛函理论计算一致。计算进一步表明，对于2和3，与 Cu-O-O-Cu 二面角变化相关的电位都很小. 这些发现为动力学简单的 1e 的低重组能提供了结构基础^- μ-1,2-超氧/过氧双铜 (II)对的相互转化，并为全面研究 Cu _x / 中的这些关键中间体打开了大门O ₂化学。

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Structurally Characterized μ-1,2-Peroxo/Superoxo Dicopper(II) Pair

Superoxo complexes of copper are primary adducts in several O₂-activating Cu-containing metalloenzymes as well as in other Cu-mediated oxidation and oxygenation reactions. Because of their intrinsically high reactivity, however, isolation of Cu_x(O₂^•–) species is challenging. Recent work (J. Am. Chem. Soc.2017, 139, 9831; 2019, 141, 12682) established fundamental thermochemical data for the H atom abstraction reactivity of dicopper(II) superoxo complexes, but structural characterization of these important intermediates was so far lacking. Here we report the first crystallographic structure determination of a superoxo dicopper(II) species (3) together with the structure of its 1e^– reduced peroxo congener (2; a rare cis-μ-1,2-peroxo dicopper(II) complex). Interconversion of 2 and 3 occurs at low potential (−0.58 V vs Fc/Fc⁺) and is reversible both chemically and electrochemically. Comparison of metric parameters (d(O–O) = 1.441(2) Å for 2 vs 1.329(7) Å for 3) and of spectroscopic signatures (ν̃(¹⁶O–¹⁶O) = 793 cm^–1 for 2 vs 1073 cm^–1 for 3) reflects that the redox process occurs at the bridging O₂-derived unit. The Cu^II–O₂^•––Cu^II complex has an S = 1/2 spin ground state according to magnetic and EPR data, in agreement with density functional theory calculations. Computations further show that the potential associated with changes of the Cu–O–O–Cu dihedral angle is shallow for both 2 and 3. These findings provide a structural basis for the low reorganization energy of the kinetically facile 1e^– interconversion of μ-1,2-superoxo/peroxo dicopper(II) couples, and they open the door for comprehensive studies of these key intermediates in Cu_x/O₂ chemistry.

更新日期：2021-07-14

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