Theoretical Study on the Formation of Ni(PR₃)(Aryl)F Complexes Observed in Ni-Catalyzed Decarbonylative C–C Coupling of Acyl Fluorides

Recently a promising, conceptually new base-free, nickel-catalyzed decarbonylative Suzuki–Miyaura coupling method was reported which employs acyl fluorides to produce transmetalation-active catalytic intermediates. In the present study we have performed computations to identify the reaction mechanism of the formation of these intermediates and to address important reactivity issues. We have contrasted the effect of two typical phosphine ligands (P = PCy₃, PPh₂Me), which show different behaviors according to two recent but separate experimental reports. We have also considered different experimental (stoichiometric and catalytic) conditions to elucidate the corresponding experimental observations. The free energy profiles of the most likely mechanisms supported the more facile formation of the transmetalation-active catalytic intermediate with PPh₂Me and also justified why the intermediate of the oxidative addition cannot be observed for this ligand. A crucial ingredient of the mechanisms is the cis–trans rearrangement in the square-planar ligand structure around the Ni­(II) center to stabilize the complexes and to facilitate the Ni insertion preceding the decarbonylation. We obtained two distinct pathways for this rearrangement: either a square-planar–tetrahedral conformational transition or a route through five-coordinated, more fluxional configurations, depending on the phosphines. In fact, molecular dynamics simulations revealed that the mobile trigonal-bipyramidal structures can remarkably simplify the decarbonylation mechanism predicted by optimization calculations, implying an even faster decarbonylation.