Department of Chemistry and Biochemistry, Concordia University, Montreal, QC H4B 1R6, Canada.
Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada.
J Am Chem Soc. 2020 Nov 11;142(45):19023-19028. doi: 10.1021/jacs.0c09300. Epub 2020 Oct 30.
Redox noninnocent ligands enhance the reactivity of the metal they complex, a strategy used by metalloenzymes and in catalysis. Herein, we report a series of copper complexes with the same ligand framework, but with a pendant nitrogen group that spans five different redox states between nitro and amine. Of particular interest is the synthesis of a unprecedented copper(I)-arylhydroxylamine complex. While hydroxylamines typically disproportionate or decompose in the presence of transition metal ions, the reactivity of this metastable species is arrested by the presence of an intramolecular hydrogen bond. Two-electron oxidation yields a copper(II)-(arylnitrosyl radical) complex that can dissociate to a copper(I) species with uncoordinated arylnitroso. This combination of ligand redox noninnocence and hemilability provides opportunities in catalysis for two-electron chemistry via a one-electron copper(I/II) shuttle, as exemplified with an aerobic alcohol oxidation.
氧化还原非中性配体增强了它们所配位的金属的反应活性，这是金属酶和催化中使用的一种策略。在此，我们报告了一系列具有相同配体框架的铜配合物，但带有一个侧挂的氮原子，它在硝基和胺基之间跨越了五个不同的氧化还原态。特别有趣的是合成了一种前所未有的铜（I）-芳基羟胺配合物。虽然羟胺通常在过渡金属离子存在下会歧化或分解，但这种亚稳态物质的反应活性被分子内氢键所阻止。两电子氧化生成铜（II）-（芳基亚硝自由基）配合物，它可以解缔合为具有未配位芳基亚硝基的铜（I）物种。这种配体氧化还原非中性和半配位的结合为通过单电子铜（I/II）穿梭进行两电子化学提供了机会，例如有氧醇氧化就是一个例子。
