Electrostatic vs. Inductive Effects in Phosphine Ligand Donor Properties, Reactivity, and Catalysis

The use of charged groups to leverage electrostatics in molecular systems is a promising strategy to tune reactivity. However, disentangling the relative influences of inductive (through-bond) and electrostatic (through-space) contributions from charged groups is a long-standing challenge. To quantify the interplay of these effects we have synthesized and analyzed the anionic phosphine, Ph2PCH2BF3−, its selenide, and its transition metal complexes. Solvent-dependent changes in donor strength consistent with Coulomb’s law support a dominant electrostatic contribution to donor strength, while computations highlight the impact of charge position and orientation. Finally, inclusion of the anion also greatly accelerates C–F oxidative addition reactivity in Ni complexes, allowing for rapid catalytic C–F borylation of fluoroarenes. These results show that covalently bound charged functionalities can exert a major electrostatic influence under common solution phase reaction conditions.