Open AccessMonovalent Nickel-Mediated Radical Formation: A Concerted Halogen-Atom Dissociation Pathway Determined by Electroanalytical Studies
Author(s) -
Qiao Lin,
Yingjuan Fu,
Peng Liu,
Tianning Diao
Publication year - 2021
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.1c05255
Subject(s) - electrophile , chemistry , photochemistry , dissociation (chemistry) , nickel , halogen , steric effects , chemoselectivity , electron transfer , computational chemistry , reaction mechanism , catalysis , stereochemistry , organic chemistry , alkyl
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.