Institute of Inorganic Chemistry, University of Göttingen, Tamannstrasse 4, D-37077 Göttingen, Germany.
Institut de Química Computacional i Catàlisi (IQCC) & Department de Química, Universitat de Girona, 17003 Girona, Spain.
J Am Chem Soc. 2021 Oct 27;143(42):17751-17760. doi: 10.1021/jacs.1c08645. Epub 2021 Oct 18.
The properties of metal/dioxygen species, which are key intermediates in oxidation catalysis, can be modulated by interaction with redox-inactive Lewis acids, but structural information about these adducts is scarce. Here we demonstrate that even mildly Lewis acidic alkali metal ions, which are typically viewed as innocent "spectators", bind strongly to a reactive peroxo dicopper(II) intermediate. Unprecedented structural insight has now been obtained from X-ray crystallographic characterization of the "bare" Cu(μ-η:η-O) motif and its Li, Na, and K complexes. UV-vis, Raman, and electrochemical studies show that the binding persists in MeCN solution, growing stronger in proportion to the cation's Lewis acidity. The affinity for Li is surprisingly high (∼70 × 10 M), leading to Li extraction from its crown ether complex. Computational analysis indicates that the alkali ions influence the entire Cu-OO-Cu core, modulating the degree of charge transfer from copper to dioxygen. This induces significant changes in the electronic, magnetic, and electrochemical signatures of the CuO species. These findings have far-reaching implications for analyses of transient metal/dioxygen intermediates, which are often studied , and they may be relevant to many (bio)chemical oxidation processes when considering the widespread presence of alkali cations in synthetic and natural environments.
金属/双氧物种的性质是氧化催化中的关键中间体，可以通过与氧化还原惰性路易斯酸相互作用进行调节，但这些加合物的结构信息很少。在这里，我们证明了即使是轻微路易斯酸性的碱金属离子，通常被视为无辜的“旁观者”，也能与活性过氧二铜（II）中间体强烈结合。现在，通过对“裸露”Cu(μ-η:η-O)基序及其 Li、Na 和 K 配合物的 X 射线晶体学表征，获得了前所未有的结构洞察力。紫外-可见、拉曼和电化学研究表明，在 MeCN 溶液中结合仍然存在，并且与阳离子的路易斯酸度成比例地增强。与 Li 的亲和力高得惊人（∼70 × 10 M），导致从其冠醚配合物中提取 Li。计算分析表明，碱离子会影响整个 Cu-OO-Cu 核心，从而调节铜到双氧的电荷转移程度。这会导致 CuO 物种的电子、磁性和电化学特征发生显著变化。这些发现对瞬态金属/双氧中间体的分析具有深远的意义，因为它们经常被研究，并且当考虑到碱阳离子在合成和自然环境中的广泛存在时，它们可能与许多（生物）化学氧化过程有关。
