The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element–hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element–hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol−1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry.
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The data that support the findings of this study are included with the Article and Supplementary Information. Crystallographic data for the structure of Ir5 reported in this Article have been deposited at the Cambridge Crystallographic Data Centre, under deposition number CCDC 2021155. Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures.Source data are provided with this paper.
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This research was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Catalysis Science Program, under Award DE-SC0006498 and the Andlinger Center for Energy and the Environment (Princeton University). S.K. acknowledges a Samsung Scholarship for partial financial support. L.T. and G.D.S. acknowledge support from the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences of the US DOE through Grant No. DE-SC0019370. G.D.S. is a CIFAR Fellow in the Bio-Inspired Energy Program. We are grateful to K. Conover (Princeton University) for assistance with photo-NMR experiments and L. Mendelsohn and D. Wang (Princeton University) for helpful discussions.
The authors declare no competing interests.
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Park, Y., Kim, S., Tian, L. et al. Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen. Nat. Chem. 13, 969–976 (2021). https://doi.org/10.1038/s41557-021-00732-z