Further Development of Weakly Coordinating Cations: Fluorinated Bis(triarylphosphoranylidene)iminium Salts

Abstract

So far unknown bis(triarylphosphoranylidene)iminium cations [PPN]⁺ with one fluorine atom in para ([PPN-1^F ]⁺ ), two in meta ([PPN-2^F ]⁺ ), or three in para and meta positions of the phenyl rings ([PPN-3^F ]⁺ ) were obtained by a newly developed one-pot reaction. These halogenated [PPN]⁺ cations were characterized by IR and Raman spectroscopy in comparison with quantum-chemical calculations, ESI⁺ mass spectrometry, NMR spectroscopy, and single-crystal X-ray diffraction. To assess their quality as weakly coordinating cations and the associated ability to stabilize labile anions, the electrostatic potential and fluoride-ion affinity were calculated and compared with those of the unsubstituted and so far unknown perfluorinated [PPN-5^F ]⁺ cations.