Synthesis of a Perfluorinated Phenoxyphosphorane and Conversion to Its Hexacoordinate Anions

We report the synthesis and structural characterization of a neutral P^V Lewis acid, P(OC₆ F₅ )₅ , and salts containing the six-coordinate anions [P(OC₆ F₅ )₅ F]^- and [P(OC₆ F₅ )₆ ]^- . The latter anion exhibits a rare example of F-π_arene interactions in both the solid and the solution phase, which has been quantitatively studied by variable-temperature (VT) NMR spectroscopy. The Lewis acid strength of P(OC₆ F₅ )₅ has been assessed through experimental fluoride ion competition experiments and quantum-chemical calculations of its fluoride ion affinity (FIA) and global electrophilicity index (GEI). Our findings highlight the importance of considering solvent effects in electrophilicity calculations, even when neutral Lewis acids are involved, and show a rare divergence between FIA and GEI trends. The coordinating abilities of the [P(OC₆ F₅ )₆ ]^- and [P(OC₆ F₅ )₅ F]^- anions towards the trityl cation, as a prototypical electrophile, have been assessed.