Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander University Erlangen-Nürnberg, Egerlandstrasse 1, D-91058 Erlangen, Germany.
Université de Toulouse, INSA, UPS, LPCNO, 135 Avenue de Rangueil, F-31077 Toulouse, France.
Nat Chem. 2018 Mar;10(3):259-267. doi: 10.1038/nchem.2899. Epub 2017 Dec 11.
The reactivity of uranium compounds towards small molecules typically occurs through stoichiometric rather than catalytic processes. Examples of uranium catalysts reacting with water are particularly scarce, because stable uranyl groups form that preclude the recovery of the uranium compound. Recently, however, an arene-anchored, electron-rich uranium complex has been shown to facilitate the electrocatalytic formation of H from HO. Here, we present the precise role of uranium-arene δ bonding in intermediates of the catalytic cycle, as well as details of the atypical two-electron oxidative addition of HO to the trivalent uranium catalyst. Both aspects were explored by synthesizing mid- and high-valent uranium-oxo intermediates and by performing comparative studies with a structurally related complex that cannot engage in δ bonding. The redox activity of the arene anchor and a covalent δ-bonding interaction with the uranium ion during H formation were supported by density functional theory analysis. Detailed insight into this catalytic system may inspire the design of ligands for new uranium catalysts.
铀化合物与小分子的反应通常通过化学计量而不是催化过程发生。铀催化剂与水反应的例子特别罕见，因为稳定的铀酰基团形成会排除铀化合物的回收。然而，最近，一种芳基锚定的富电子铀配合物已被证明能够促进从 HO 中电化学形成 H。在这里，我们展示了铀-芳基 δ 键在催化循环中间体中的精确作用，以及 HO 对三价铀催化剂的非典型两电子氧化加成的详细信息。这两个方面都是通过合成中价和高价铀-氧中间体以及与不能参与 δ 键合的结构相关的配合物进行比较研究来探索的。芳基锚定的氧化还原活性以及在 H 形成过程中与铀离子的共价 δ 键合相互作用得到了密度泛函理论分析的支持。对该催化体系的详细了解可能会激发新型铀催化剂配体的设计。
