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Large-scale CO2 hydrogenation could offer a renewable stream of industrially important C1 chemicals while reducing CO2 emissions. Critical to this opportunity is the requirement for inexpensive catalysts based on earth-abundant metals instead of precious metals. We report a nickel-gallium complex featuring a Ni(0)→ Ga(III) bond that shows remarkable catalytic activity for hydrogenating CO2 to formate at ambient temperature (3150 turnovers, turnover frequency = 9700 h-1), compared with prior homogeneous Ni-centered catalysts. The Lewis acidic Ga(III) ion plays a pivotal role in stabilizing catalytic intermediates, including a rare anionic d10 Ni hydride. Structural and in situ characterization of this reactive intermediate support a terminal Ni-H moiety, for which the thermodynamic hydride donor strength rivals those of precious metal hydrides. Collectively, our experimental and computational results demonstrate that modulating a transition metal center via a direct interaction with a Lewis acidic support can be a powerful strategy for promoting new reactivity paradigms in base-metal catalysis.
Bibliographical noteFunding Information:
R.C.C. and M.V.V. were supported by DOE Office of Science Graduate Student Research and National Science Foundation (NSF) Graduate Research Fellowship programs, respectively. J.X., J.Y., and L.G. were supported as part of the Inorganometallic Catalyst Design Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under Award DE-SC0012702. J.C.L., S.A.B., and A.M.A. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. C.C.L. acknowledges the NSF (CHE-1665010) for support. The authors acknowledge Dr. Victor Young, Jr. for assistance with X-ray crystallography. R.C.C. thanks Dr. Christopher Zall and Dr. Eric Wiedner for helpful suggestions. C.C.L. thanks Dr. Morris Bullock (PNNL) for cosponsoring the DOE graduate research fellowship to R.C.C.
© 2017 American Chemical Society.