Monovalent Nickel-Mediated Radical Formation: A Concerted Halogen-Atom Dissociation Pathway Determined by Electroanalytical Studies.
| Autor: | Lin Q; Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States., Fu Y; Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States., Liu P; Department of Chemistry, University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States., Diao T; Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, United States. |
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| Jazyk: | angličtina |
| Zdroj: | Journal of the American Chemical Society [J Am Chem Soc] 2021 Sep 08; Vol. 143 (35), pp. 14196-14206. Date of Electronic Publication: 2021 Aug 25. |
| DOI: | 10.1021/jacs.1c05255 |
| Abstrakt: | The recent success of nickel catalysts in stereoconvergent cross-coupling and cross-electrophile coupling reactions partly stems from the ability of monovalent nickel species to activate C(sp 3 ) electrophiles and generate radical intermediates. This electroanalytical study of the commonly applied (bpy)Ni catalyst elucidates the mechanism of this critical step. Data rule out outer-sphere electron transfer and two-electron oxidative addition pathways. The linear free energy relationship between rates and the bond-dissociation free energies, the electronic and steric effects of the nickel complexes and the electrophiles, and DFT calculations support a variant of the halogen-atom abstraction pathway, the inner-sphere electron transfer concerted with halogen-atom dissociation. This mechanism accounts for the observed reactivity of different electrophiles in cross-coupling reactions and provides a mechanistic rationale for the chemoselectivity obtained in cross-electrophile coupling over homocoupling. |
| Databáze: | MEDLINE |
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