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Photogenerated Ni(I)–Bipyridine Halide Complexes: Structure-Function Relationships for Competitive C(sp²)–Cl Oxidative Addition and Dimerization Reactivity Pathways

Cagan, David A. and Bím, Daniel and McNicholas, Brendon J. and Kazmierczak, Nathanael P. and Oyala, Paul H. and Hadt, Ryan G. (2023) Photogenerated Ni(I)–Bipyridine Halide Complexes: Structure-Function Relationships for Competitive C(sp²)–Cl Oxidative Addition and Dimerization Reactivity Pathways. . (Unpublished)

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We report the facile photochemical generation of a library of Ni(I)–bpy halide complexes (Ni(I)(ᴿbpy)X (R = t-Bu, H, MeOOC; X = Cl, Br, I) and benchmark their relative reactivity toward competitive oxidative addition and off-cycle dimerization pathways. Structure-function relationships between ligand set and reactivity are developed, with a particular emphasis on rationalizing previously uncharacterized ligand-controlled reactivity toward high energy and challenging C(sp²)–Cl bonds. Through a dual Hammett and computational analysis, the mechanism of the formal oxidative addition is found to proceed through an SNAr-type pathway, consisting of a nucleophilic two-electron transfer between the Ni(I) 3d(z²) orbital and the C_(aryl)–Cl σ* orbital, which contrasts the mechanism previously observed for activation of weaker C(sp²)–Br/I bonds. The bpy substituent provides a strong influence on reactivity, ultimately determining whether oxidative addition or dimerization even occur. Here we elucidate the origin of this substituent influence as arising from perturbations to the effective nuclear charge (Zeff) of the Ni(I) center. Electron donation to the metal decreases Zeff, which leads to a significant destabilization of the entire 3d orbital manifold. Decreasing the 3d(z²) electron binding energies leads to a powerful two-electron donor to activate strong C(sp²)–Cl bonds. These changes also prove to have an analogous effect on dimerization, with decreases in Zeff leading to more rapid dimerization. Ligand-induced modulation of Zeff and the 3d(z²) orbital energy is thus a tunable target by which the reactivity of Ni(I) complexes can be altered, providing a direct route to stimulate reactivity with even stronger C–X bonds and potentially unveiling new ways to accomplish Ni-mediated photocatalytic cycles.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Cagan, David A.0000-0002-4719-2789
Bím, Daniel0000-0003-3100-4293
McNicholas, Brendon J.0000-0002-3654-681X
Kazmierczak, Nathanael P.0000-0002-7822-6769
Oyala, Paul H.0000-0002-8761-4667
Hadt, Ryan G.0000-0001-6026-1358
Additional Information:The content is available under CC BY NC ND 4.0 License. D.A.C. is a National Science Foundation Graduate Research Fellow (DGE-1745301) and is supported by a National Academies of Science, Engineering, and Medicine Ford Foundation Predoctoral Fellowship. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 883987 (D.B.). N.P.K. acknowledges support from the Hertz Fellowship and from the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1745301. The Caltech EPR facility acknowledges support from the Beckman Institute and the Dow Next Generation Educator Fund. Support has been provided by the National Institutes of Health (National Institute of General Medical Sciences, R35-GM142595). The computations presented here were conducted in the Resnick High Performance Computing Center, a facility supported by Resnick Sustainability Institute at the California Institute of Technology. The authors declare no competing financial interest.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1745301
National Academy of SciencesUNSPECIFIED
Ford FoundationUNSPECIFIED
Marie Curie Fellowship883987
Fannie and John Hertz FoundationUNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Dow Next Generation Educator FundUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Record Number:CaltechAUTHORS:20230324-457164000.12
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:120407
Deposited By: George Porter
Deposited On:30 Mar 2023 02:14
Last Modified:30 Mar 2023 02:14

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