The fine balance between one cross-coupling and two beta-hydride elimination pathways: a DFT mechanistic study of Ni(pi-allyl)(2)-catalyzed cross-coupling of alkyl halides and alkyl Grignard reagents.

The model cross-coupling of EtBr with EtMgCl mediated by Ni(pi-allyl)(2) proceeds by a catalytic cycle commencing with transmetalation establishing a novel Mg-allyl interaction, followed by Mg-assisted oxidative addition (the rate-determining step), followed by reductive elimination having much lower barrier than 2 competing beta-hydride elimination pathways, and completed by departure of MgBrCl.