Tetrafluoroammonium

The tetrafluoroammonium cation (also known as perfluoroammonium) is a positively charged polyatomic ion with chemical formula NF+
4. It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced by fluorine. Tetrafluoroammonium ion is isoelectronic with tetrafluoromethane CF
4 and the tetrafluoroborate BF−
4 anion.

The tetrafluoroammonium ion forms salts with a large variety of fluorine-bearing anions. These include the bifluoride anion (HF−
2), tetrafluorobromate (BrF−
4), metal pentafluorides (XF−
5 where X is Ge, Sn, or Ti), hexafluorides (XF−
6 where X is P, As, Sb, Bi, or Pt), heptafluorides (XF−
7 where X is W, U, or Xe), octafluorides (XeF2−
8), various oxyfluorides (XF
5O−
where X is W or U; FSO−
3, BrF
4O−
), and perchlorate (ClO−
4). Attempts to make the nitrate salt, NF
4NO
3, were unsuccessful because of quick fluorination: NF+
4 + NO−
3 → NF
3 + FONO
2.

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