A model for C-F activation by electrophilic phosphonium cations.

The synthesis of the electrophilic phosphonium cation (EPC) salt [C10 H6 (CF3 )PF(C6 F5 )2 ][B(C6 F5 )4 ] 4 was achieved via oxidation of phosphine [C10 H6 (CF3 )P(C6 F5 )2 ] 2 with XeF2 to form phosphorane [C10 H6 (CF3 )PF2 (C6 F5 )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.