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Use of a PCET Mediator Enables a Ni-HER Electrocatalyst to Act as a Hydride Delivery Agent

Derosa, Joseph and Garrido-Barros, Pablo and Li, Mengdi and Peters, Jonas C. (2022) Use of a PCET Mediator Enables a Ni-HER Electrocatalyst to Act as a Hydride Delivery Agent. Journal of the American Chemical Society, 144 (43). pp. 20118-20125. ISSN 0002-7863. doi:10.1021/jacs.2c09786.

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The generation of metal hydride intermediates during reductive electrocatalysis in the presence of acid most commonly leads to the hydrogen evolution reaction (HER). Redirecting the reactivity profile of such hydride intermediates toward the reduction of unsaturated substrates is an exciting opportunity in catalysis but presents a challenge in terms of catalyst selectivity. In this study, we demonstrate that a prototypical phosphine-supported Ni-HER catalyst can be repurposed toward the electrocatalytic reduction of a model substrate, methyl phenylpropiolate, via hydride transfer from a Ni^(ɪɪ)–H when interfaced with a metallocene-derived proton-coupled electron transfer (PCET) mediator. Key to success is generation of the Ni^(ɪɪ)–H at a potential pinned to that of the PCET mediator which is appreciably anodic of the onset of HER. Electrochemical, spectroscopic, and theoretical data point to a working mechanism where a PCET step from the metallocene-derived mediator to Ni^(ɪɪ) generates Ni^(ɪɪɪ)–H and is rate-determining; the latter Ni^(ɪɪɪ)–H is then readily reduced to a Ni^(ɪɪ)–H, which is competent for substrate reduction. Additional studies show that this tandem PCET-mediated hydride generation can afford high stereoselectivity (e.g., >20:1 Z/E using a phosphine-cobalt precatalyst with ethyl 2–heptynoate) and can also be used for the reduction of α,β-unsaturated ketones.

Item Type:Article
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URLURL TypeDescription
Derosa, Joseph0000-0001-8672-4875
Garrido-Barros, Pablo0000-0002-1489-3386
Li, Mengdi0000-0002-6198-8396
Peters, Jonas C.0000-0002-6610-4414
Additional Information:We thank the Dow Next Generation Educator Funds and Instrumentation Grants for their support of the NMR facility at Caltech. We also thank the Resnick Water and Environment Laboratory at Caltech for the use of their instrumentation. The authors are grateful to the Department of Energy Basic Energy Sciences for support via grant no. DE-SC0019136 and also to the American Chemical Society Petroleum Research Fund (PRF# 61951-ND3). J.D. thanks the Arnold and Mabel Beckman Foundation for a postdoctoral fellowship, P.G.-B. thanks the Ramón Areces Foundation for a postdoctoral fellowship, and J.C.P. is grateful to the Resnick Sustainability Institute.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0019136
Ramón Areces FoundationUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
American Chemical Society Petroleum Research Fund61951-ND3
Resnick Sustainability InstituteUNSPECIFIED
Issue or Number:43
Record Number:CaltechAUTHORS:20221128-494241100.4
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118050
Deposited By: Research Services Depository
Deposited On:07 Dec 2022 16:55
Last Modified:07 Dec 2022 16:55

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