Measuring and Leveraging Electrostatic Effects in a Charged Phosphine

Local electric fields have recently been investigated for optimizing reactivity in synthetic systems. However, disentangling the relative contributions of inductive (through-bond) and electrostatic (through-space) effects in molecular systems has been a long-standing challenge. To understand the interplay of these effects and leverage electrostatic influences for enhanced reactivity, we have synthesized a distally charged phosphine, Ph₂PCH₂BF₃⁻, and studied the effect of the charged trifluoroborate group on its donor properties and reactivity. This charged phosphine displays solvent-dependent changes in donor strength as measured by the J_P-Se of the corresponding phosphine selenide. The variation with solvent dielectric illustrates a significant electrostatic component to the donor strength. Computations further support the importance of electrostatic contributions and highlight the effect of charge position and orientation. Finally, this charged group also greatly accelerates C–F oxidative addition reactivity in Ni complexes, experimentally

verifying recent theoretical predictions. These results show that covalently bound charged functionalities can exert a significant electrostatic influence even under common solution phase reaction conditions.