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Published June 7, 2016 | Supplemental Material + Published
Journal Article Open

Proton–hydride tautomerism in hydrogen evolution catalysis

Abstract

Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H_2 production can be obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e^– + 2H^+ → H_2 catalysis. This intermediate, obtained by treatment of Cp*Rh(bpy) (Cp*, η^5-pentamethylcyclopentadienyl; bpy, κ^2-2,2′-bipyridyl) with acid, is not a hydride species but rather, bears [η^4-Cp*H] as a ligand. Delivery of a second proton to this species leads to evolution of H_2 and reformation of η^5-Cp* bound to rhodium(III). With suitable choices of acids and bases, the Cp*Rh(bpy) complex catalyzes facile and reversible interconversion of H^+ and H_2.

Additional Information

© 2016 National Academy of Sciences. Contributed by Harry B. Gray, April 17, 2016 (sent for review February 4, 2016; reviewed by Alexander Miller and David Milstein). Published online before print May 24, 2016. S.I.J. thanks Dr. Robert Nielsen for helpful discussions. This research, which was carried out in part at the Molecular Materials Research Center and the Laser Resource Center of the Beckman Institute (California Institute of Technology), was supported by NSF CCI Solar Fuels Program CHE-1305124. S.I.J. and J.D.B. acknowledge fellowships from the Resnick Sustainability Institute at Caltech. Author contributions: S.I.J., D.G.V., J.R.W., H.B.G., and J.D.B. designed research; L.M.A.Q., S.I.J., S.L.C., W.V., M.K.T., and J.D.B. performed research; W.A.G. contributed new reagents/analytic tools; L.M.A.Q., S.I.J., S.L.C., W.V., M.K.T., D.G.V., J.R.W., H.B.G., and J.D.B. analyzed data; and S.I.J., J.R.W., H.B.G., and J.D.B. wrote the paper. Reviewers: A.M., University of North Carolina; and D.M., The Weizmann Institute of Science. The authors declare no conflict of interest. Data deposition: The atomic coordinates and structure factors have been deposited in the Cambridge Crystallographic Data Centre (accession no. 1424707). This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1606018113/-/DCSupplemental.

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September 22, 2023
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