Fluoro-nitrogen Cations

The crystal structures of [NH₃ F]⁺ [CF₃ SO₃ ]^- , [NH₂ F₂ ]⁺ [SbF₆ ]^- , and [N₂ F₃ ]⁺ [Sb₃ F₁₆ ]^- have been determined, representing the first structural characterizations of these simple fluoro-nitrogen cations. The influences of the hybridization of the central nitrogen atom and of the number of fluorine substituents on the N-F bond lengths are evaluated for the series N₂ F⁺ , N₂ F₃ ⁺ , NF₂ O⁺ , NH₃ F⁺ , NH₂ F₂ ⁺ , and NF₄ ⁺ . It is shown that the N-F bond length decreases from 1.40 Å to 1.26 Å with increasing fluorine substitution and increasing s-character of the nitrogen atom, and that unusual N-F bond lengths reported in the previous literature are caused by disorder problems.