We report the synthesis and structural characterization of a neutral PV 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-πarene 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.
Keywords: Lewis acids; organofluorine groups; phosphorus; pi interactions; weakly coordinating anions.
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