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 It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced by fluorine.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 CF4, trifluoramine oxide ONF3 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 (MF−5 where M is Ge, Sn, or Ti), hexafluorides (MF−6 where M is P, As, Sb, Bi, or Pt), heptafluorides (MF−7 where M is W, U, or Xe), octafluorides (XeF2−8), various oxyfluorides (MF5O− where M is W or U; FSO−3, BrF4O−), and perchlorate (ClO−4). Attempts to make the nitrate salt, NF4NO3, were unsuccessful because of quick fluorination: NF+4 + NO−3 → NF3 + FONO2. (Wikipedia).
