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Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen

Abstract

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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Fig. 1: Strategies to synthesize weak chemical bonds.
Fig. 2: Proof-of-concept for photoinduced catalytic PCET using H2.
Fig. 3: N–H and O–H bond formation by catalytic PCET using H2 as the reductant.
Fig. 4: Mechanistic investigations.
Fig. 5: Photophysical studies on the excited states of Ir2.
Fig. 6: General applicability of photoinduced catalytic PCET of H2.

Data availability

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.

References

  1. 1.

    Warren, J. J., Tronic, T. A. & Mayer, J. M. Thermochemistry of proton-coupled electron transfer reagents and its implications. Chem. Rev. 110, 6961–7001 (2010).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  2. 2.

    Stubbe, J., Nocera, D. G., Yee, C. S. & Chang, M. C. Y. Radical initiation in the class I ribonucleotide reductase: long-range proton-coupled electron transfer? Chem. Rev. 103, 2167–2202 (2003).

    CAS  PubMed  Article  Google Scholar 

  3. 3.

    Meyer, T. J., Huynh, M. H. V. & Thorp, H. H. The possible role of proton-coupled electron transfer (PCET) in water oxidation by photosystem II. Angew. Chem. Int. Ed. 46, 5284–5304 (2007).

    CAS  Article  Google Scholar 

  4. 4.

    Bezdek, M. J., Guo, S. & Chirik, P. J. Coordination-induced weakening of ammonia, water, and hydrazine X–H bonds in a molybdenum complex. Science 354, 730–733 (2016).

    CAS  PubMed  Article  Google Scholar 

  5. 5.

    Bezdek, M. J., Pappas, I. & Chirik, P. J. in Nitrogen Fixation (ed. Nishibayashi, Y.) 1–21 (Springer International Publishing, 2017).

  6. 6.

    Bezdek, M. J. & Chirik, P. J. A fresh approach to ammonia synthesis. Nature 568, 464–466 (2019).

    CAS  PubMed  Article  Google Scholar 

  7. 7.

    Gentry, E. C. & Knowles, R. R. Synthetic applications of proton-coupled electron transfer. Acc. Chem. Res. 49, 1546–1556 (2016).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  8. 8.

    Chalkley, M. J. et al. Catalytic N2-to-NH3 conversion by Fe at lower driving force: a proposed role for metallocene-mediated PCET. ACS Cent. Sci. 3, 217–223 (2017).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  9. 9.

    Nicolaou, K. C., Ellery, S. P. & Chen, J. S. Samarium diiodide mediated reactions in total synthesis. Angew. Chem. Int. Ed. 48, 7140–7165 (2009).

    CAS  Article  Google Scholar 

  10. 10.

    Kolmar, S. S. & Mayer, J. M. SmI2(H2O)n reduction of electron rich enamines by proton-coupled electron transfer. J. Am. Chem. Soc. 139, 10687–10692 (2017).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  11. 11.

    Ashida, Y., Arashiba, K., Nakajima, K. & Nishibayashi, Y. Molybdenum-catalysed ammonia production with samarium diiodide and alcohols or water. Nature 568, 536–540 (2019).

    CAS  PubMed  Article  Google Scholar 

  12. 12.

    Lennox, J. C., Kurtz, D. A., Huang, T. & Dempsey, J. L. Excited-state proton-coupled electron transfer: different avenues for promoting proton/electron movement with solar photons. ACS Energy Lett. 2, 1246–1256 (2017).

    CAS  Article  Google Scholar 

  13. 13.

    Pannwitz, A. & Wenger, O. S. Proton coupled electron transfer from the excited state of a ruthenium(ii) pyridylimidazole complex. Phys. Chem. Chem. Phys. 18, 11374–11382 (2016).

    PubMed  Article  Google Scholar 

  14. 14.

    Martinez, K., Stash, J., Benson, K. R., Paul, J. J. & Schmehl, R. H. Direct observation of sequential electron and proton transfer in excited-state ET/PT Reactions. J. Phys. Chem. C 123, 2728–2735 (2019).

    CAS  Article  Google Scholar 

  15. 15.

    Schreier, M. R., Pfund, B., Guo, X. & Wenger, O. S. Photo-triggered hydrogen atom transfer from an iridium hydride complex to unactivated olefins. Chem. Sci. 11, 8582–8594 (2020).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  16. 16.

    Smith, D. M., Pulling, M. E. & Norton, J. R. Tin-free and catalytic radical cyclizations. J. Am. Chem. Soc. 129, 770–771 (2007).

    CAS  PubMed  Article  Google Scholar 

  17. 17.

    Yao, C., Dahmen, T., Gansäuer, A. & Norton, J. Anti-Markovnikov alcohols via epoxide hydrogenation through cooperative catalysis. Science 364, 764–767 (2019).

    CAS  PubMed  Article  Google Scholar 

  18. 18.

    Hu, Y. & Norton, J. R. Kinetics and thermodynamics of H/H•/H+ transfer from a rhodium(iii) hydride. J. Am. Chem. Soc. 136, 5938–5948 (2014).

    CAS  PubMed  Article  Google Scholar 

  19. 19.

    Pappas, I. & Chirik, P. J. Ammonia synthesis by hydrogenolysis of titanium–nitrogen bonds using proton coupled electron transfer. J. Am. Chem. Soc. 137, 3498–3501 (2015).

    CAS  PubMed  Article  Google Scholar 

  20. 20.

    Kim, S., Zhong, H., Park, Y., Loose, F. & Chirik, P. J. Catalytic hydrogenation of a manganese(v) nitride to ammonia. J. Am. Chem. Soc. 142, 9518–9524 (2020).

    CAS  PubMed  Article  Google Scholar 

  21. 21.

    Choi, J., Pulling, M. E., Smith, D. M. & Norton, J. R. Unusually weak metal−hydrogen bonds in HV(CO)4(P−P) and their effectiveness as H donors. J. Am. Chem. Soc. 130, 4250–4252 (2008).

    CAS  PubMed  Article  Google Scholar 

  22. 22.

    Choi, J., Tang, L. & Norton, J. R. Kinetics of hydrogen atom transfer from (η5-C5H5)Cr(CO)3H to various olefins: influence of olefin Structure. J. Am. Chem. Soc. 129, 234–240 (2007).

    CAS  PubMed  Article  Google Scholar 

  23. 23.

    Borowski, A. F., Vendier, L., Sabo-Etienne, S., Rozycka-Sokolowska, E. & Gaudyn, A. V. Catalyzed hydrogenation of condensed three-ring arenes and their N-heteroaromatic analogues by a bis(dihydrogen) ruthenium complex. Dalton Trans. 41, 14117–14125 (2012).

    CAS  PubMed  Article  Google Scholar 

  24. 24.

    Han, B., Ma, P., Cong, X., Chen, H. & Zeng, X. Chromium- and cobalt-catalyzed, regiocontrolled hydrogenation of polycyclic aromatic hydrocarbons: a combined experimental and theoretical study. J. Am. Chem. Soc. 141, 9018–9026 (2019).

    CAS  PubMed  Article  Google Scholar 

  25. 25.

    Feder, H. M. & Halpern, J. Mechanism of the cobalt carbonyl-catalyzed homogeneous hydrogenation of aromatic hydrocarbons. J. Am. Chem. Soc. 97, 7186–7188 (1975).

    CAS  Article  Google Scholar 

  26. 26.

    Szostak, M., Spain, M. & Procter, D. J. Determination of the effective redox potentials of SmI2, SmBr2, SmCl2, and their complexes with water by reduction of aromatic hydrocarbons. Reduction of anthracene and stilbene by samarium(ii) iodide–water complex. J. Org. Chem. 79, 2522–2537 (2014).

    CAS  PubMed  Article  Google Scholar 

  27. 27.

    Chciuk, T. V. & Flowers, R. A. Proton-coupled electron transfer in the reduction of arenes by SmI2–water complexes. J. Am. Chem. Soc. 137, 11526–11531 (2015).

    CAS  PubMed  Article  Google Scholar 

  28. 28.

    Chatterjee, A. & König, B. Birch-type photoreduction of arenes and heteroarenes by sensitized electron transfer. Angew. Chem. Int. Ed. 58, 14289–14294 (2019).

    CAS  Article  Google Scholar 

  29. 29.

    Leoni, P., Landi, A. & Pasquali, M. Isolation of the first neutral chromium formyl derivatives. J. Organomet. Chem. 321, 365–369 (1987).

    CAS  Article  Google Scholar 

  30. 30.

    Bandy, J. A. et al. Decamethylrhenocene, (η5-C5Me5)2Re. J. Am. Chem. Soc. 110, 5039–5050 (1988).

    CAS  Article  Google Scholar 

  31. 31.

    Hu, Y. et al. Synthesis, electrochemistry, and reactivity of new iridium(iii) and rhodium(iii) hydrides. Organometallics 31, 5058–5064 (2012).

    CAS  Article  Google Scholar 

  32. 32.

    Deaton, J. C. et al. Excited-state switching between ligand-centered and charge transfer modulated by metal–carbon bonds in cyclopentadienyl iridium complexes. Inorg. Chem. 57, 15445–15461 (2018).

    CAS  PubMed  Article  Google Scholar 

  33. 33.

    Barrett, S. M. et al. Mechanistic basis for tuning iridium hydride photochemistry from H2 evolution to hydride transfer hydrodechlorination. Chem. Sci. 11, 6442–6449 (2020).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  34. 34.

    Chalkley, M. J., Drover, M. W. & Peters, J. C. Catalytic N2-to-NH3 (or -N2H4) conversion by well-defined molecular coordination complexes. Chem. Rev. 120, 5582–5636 (2020).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  35. 35.

    Nishibayashi, Y., Iwai, S. & Hidai, M. Bimetallic system for nitrogen fixation: ruthenium-assisted protonation of coordinated N2 on tungsten with H2. Science 279, 540–542 (1998).

    CAS  PubMed  Article  Google Scholar 

  36. 36.

    Reiners, M. et al. NH3 formation from N2 and H2 mediated by molecular tri-iron complexes. Nat. Chem. 12, 740–746 (2020).

    PubMed  Article  CAS  Google Scholar 

  37. 37.

    Park, Y., Semproni, S. P., Zhong, H., Chirik, P. J. Synthesis, electronic structure, and reactivity of a planar four-coordinate, cobalt–imido complex. Angew. Chem. Int. Ed. https://doi.org/10.1002/anie.202104320 (2021).

  38. 38.

    Gianetti, T. L., La Pierre, H. S. & Arnold, J. Group 5 imides and bis(imide)s as selective hydrogenation catalysts. Eur. J. Inorg. Chem. 2013, 3771–3783 (2013).

    CAS  Article  Google Scholar 

  39. 39.

    Iwasaki, K., Wan, K. K., Oppedisano, A., Crossley, S. W. M. & Shenvi, R. A. SImple, chemoselective hydrogenation with thermodynamic stereocontrol. J. Am.Chem. Soc. 136, 1300–1303 (2014).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  40. 40.

    Bullock, R. M. & Samsel, E. G. Hydrogen atom transfer reactions of transition-metal hydrides. Kinetics and mechanism of the hydrogenation of ɑ-cyclopropylstyrene by metal carbonyl hydrides. J. Am. Chem. Soc. 112, 6886–6898 (1990).

    CAS  Article  Google Scholar 

  41. 41.

    Gunasekara, T. et al. TEMPO-mediated catalysis of the sterically hindered hydrogen atom transfer reaction between (C5Ph5)Cr(CO)3H and a trityl radical. J. Am. Chem. Soc. 141, 1882–1886 (2019).

    CAS  PubMed  Article  Google Scholar 

  42. 42.

    Kim, S., Loose, F., Bezdek, M. J., Wang, X. & Chirik, P. J. Hydrogenation of N-heteroarenes using rhodium precatalysts: reductive elimination leads to formation of multimetallic clusters. J. Am. Chem. Soc. 141, 17900–17908 (2019).

    CAS  PubMed  Article  Google Scholar 

  43. 43.

    Barrett, S. M., Pitman, C. L., Walden, A. G. & Miller, A. J. M. Photoswitchable hydride transfer from iridium to 1-methylnicotinamide rationalized by thermochemical cycles. J. Am. Chem. Soc. 136, 14718–14721 (2014).

    CAS  PubMed  Article  Google Scholar 

  44. 44.

    Solis, B. H. & Hammes-Schiffer, S. Substituent effects on cobalt diglyoxime catalysts for hydrogen evolution. J. Am. Chem. Soc. 133, 19036–19039 (2011).

    CAS  PubMed  Article  Google Scholar 

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Acknowledgements

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.

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Y.P., S.K. and P.J.C. conceived the project and designed the initial experiments. Y.P. and P.J.C. wrote the manuscript. Y.P. performed experiments regarding the synthesis and characterization of the metal complexes and the organic compounds and computational calculations. Y.P. and L.T. performed photophysical measurements under the supervision of G.D.S. Single-crystal X-ray diffraction analysis was performed by H.Z. All authors analysed the data, discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Paul J. Chirik.

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Extended data

Extended Data Fig. 1

Gibbs free energy surface of the catalytic process was estimated based on thermochemical data from photophysical measurements and computational analysis.

Supplementary information

Supplementary Information

Supplementary Figs. 1–71, Note 1, Tables 1–10.

Supplementary Data

Source data

Source Data Fig. 2

Plot of data points for Fig. 2c,d.

Source Data Fig. 4

Plot of data points for Fig. 4d and its inset.

Source Data Fig. 5

Plot of data points for Fig. 5a,c and its inset.

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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

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