Abstract
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 H2 from H2O. 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 H2O 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 H2 formation were supported by density functional theory analysis. Detailed insight into this catalytic system may inspire the design of ligands for new uranium catalysts.
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Acknowledgements
The authors thank H.S. La Pierre for discussions and M.E. Miehlich for assistance with EPR spectroscopy. D.P.H. acknowledges support from the Graduate School of Molecular Science (GSMS) of FAU Erlangen-Nürnberg. The Bundesministerium für Bildung und Forschung (BMBF, support codes 02NUK012C and 02NUK020C), the FAU Erlangen-Nürnberg and COST Action CM1006 are acknowledged for funding.
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D.P.H. and K.M. planned the research and prepared the manuscript. D.P.H. performed the experiments. F.W.H. conducted the XRD analyses and refined structures. L.M. performed theoretical calculations and analyses. All authors edited and reviewed the manuscript in the context of their contributions. K.M. supervised all aspects of the project.
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Halter, D., Heinemann, F., Maron, L. et al. The role of uranium–arene bonding in H2O reduction catalysis. Nature Chem 10, 259–267 (2018). https://doi.org/10.1038/nchem.2899
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DOI: https://doi.org/10.1038/nchem.2899
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