Properties of Tetrafluoroammonium Salts

Compound Tetragonal unit cell dimensions (pm) Density (g/cm3) Reference 

The 19F NMR spectrum of NF4+ salts consists of a triplet centered around 210-228 ppm downfield from CFC13, with JNF 230 Hz. The bandwidth at half-height does not exceed 10 Hz, indicating that there is no N-F quadrupole coupling. The existence of this triplet and no other resonance attributable to NF structure shows that all fluorine atoms in NF4+ are equivalent and that the structure of the ion is tetrahedral. 

X-Ray powder diffraction data of a large number of NF4+ salts are described by various workers. The data (Table I) indicate these salts have a tetragonal lattice. Single crystals of 98.9% pure (NF4)2NiF6 showed that the compound has a body-centered tetragonal cell, space group /4/m (37). The salt is made up of octahedral NiF62- ions and tetrahedral NF4+ cations and has the antifluorite structure. The interatomic N-F distance in the NF4+ tetrahedron is 130-140 pm and the F---F distance is 220 pm. 

There are three oxyfluorides of nitrogen, two of which, NOF and NOjF, are well known and will not be dealt with here. The third, trifluoroamine oxide, is less familiar and was isolated comparatively recently at roughly the same time by three independent groups. Fox and his co-workers made the compound in 10-15% yield by passing an NF3-02 mixture at a pressure of 10-15 mm through an electrical 

Observations on the properties of the compound made by these early authors are referred to later. 

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