Mechanistic insight into Ni(i)-catalyzed regioselective alkene hydroarylation: is it carbonickelation or hydronickelation?†

This density functional theory (DFT) study explores the reaction mechanism of nickel-catalyzed hydroarylation of unactivated alkenes that selectively generates branched (Markovnikov) products. Extensive DFT calculations have revealed a novel and plausible mechanism via hydronickelation, which differs from the originally proposed pathway through carbonickelation. The N-heterocyclic carbene-anchored catalyst IPrNiOi-Pr favors β-hydride elimination from the alkoxide ligand over oxidative addition with carbon electrophiles. This chemoselectivity results in the formation of the Ni(I) hydride complex IPrNiH, initiating a hydronickelation pathway involving alkene into Ni–H insertion, PhOTf oxidative addition, and alkyl–phenyl reductive elimination. The β-hydride elimination represents the rate-limiting step, while the oxidative addition of PhOTf determines the regioselectivity, which is sterically controlled. This DFT study demonstrates a robust theoretical–experimental synergy and provides new mechanistic insights valuable for reaction development.