A model for C–F activation by electrophilic phosphonium cations

Abstract

The synthesis of the electrophilic phosphonium cation (EPC) salt [C₁₀H₆(CF₃)PF(C₆F₅)₂][B(C₆F₅)₄] 4 was achieved via oxidation of phosphine [C₁₀H₆(CF₃)P(C₆F₅)₂] 2 with XeF₂ to form phosphorane [C₁₀H₆(CF₃)PF₂(C₆F₅)₂] 3 and subsequent fluoride ion abstraction. Structural and spectroscopic characterization of 4 provides evidence of an interaction between the CF₃ functionality and the phosphonium centre. AIM and NBO analyses also support donation from a lone pair on a fluorine atom of the CF₃ group to the P–F σ* orbital of the fluorophosphonium unit, consistent with previously proposed mechanisms for main group C–F bond activations.