Heterolytic versus Homolytic: Theoretical Insight into the Ni0-Catalyzed Ph-F Bond Activation

The Ni-0-catalyzed borylation of fluorobenzene (PhF) was theoretically investigated. Density functional theory (DFT) calculations disclosed that the Ph-F bond activation occurred heterolytically via an unprecedented nucleophilic aromatic substitution reaction (SNAr) assisted by an sp(2)-sp(3) diboron complex [B(2)nep(2)center dot(OPh)]-Na+, which forms a Ni-0-ate complex as an active species. The diboron-ate complex stabilizes the transition state of the Ph-F bond activation through three interactions, a Ni center dot center dot center dot O coordination, a Na+center dot center dot center dot F cationic dipole interaction, and a charge transfer arising from NaOPh. On the other hand, the Ph-F bond activation catalyzed by Ni-0(dcpe) and Ni-0(PCy3)(2) complexes has also been studied to allow a comparison between the monophosphine and bisphosphine ligands. Results suggest that Ni-0(PCy3)(2) is less effective than Ni-0(dcpe) for the concerted oxidative addition of the Ph-F bond because the Ni dp orbital of Ni-0(PCy3)(2) is at a lower energy level than that of Ni-0(dcpe) in the equilibrium geometry. The characteristic molecular orbital features of Ni-0-catalyzed Ph-F bond activation via both the nucleophilic aromatic substitution reaction (heterolytic) and the concerted oxidative addition (homolytic) were theoretically disclosed.

Automated summary

The Ni-0-catalyzed borylation of fluorobenzene mechanism was theoretically investigated using density functional theory (DFT) calculations. It was found that the reaction proceeds through an unprecedented nucleophilic aromatic substitution reaction assisted by an sp(2)-sp(3) diboron complex. The study also compared the catalytic effects of mono- and bisphosphine ligands, finding that Ni-0(dcpe) is more effective. Theoretical analysis revealed the molecular orbital features of the Ni-0-catalyzed Ph-F bond activation via both nucleophilic aromatic substitution and concerted oxidative addition reactions.