Tetrafluoroammonium

The geometry of the tetrafluoroammonium ion is tetrahedral, with an estimated nitrogen-fluorine bond length of 124 pm. All fluorine atoms are in equivalent positions. == Synthesis ==

Tetrafluoroammonium salts are prepared by oxidising nitrogen trifluoride with fluorine in the presence of a strong Lewis acid which acts as a fluoride ion acceptor. The original synthesis by Tolberg, Rewick, Stringham, and Hill in 1966 employs antimony pentafluoride as the Lewis acid: : + + → salts can also be prepared by fluorination of with krypton difluoride () and fluorides of the form , where M is Sb, Nb, Pt, Ti, or B. For example, reaction of with and yields . Many tetrafluoroammonium salts can be prepared with metathesis reactions. == Reactions ==

Tetrafluoroammonium salts are extremely hygroscopic. The ion, when dissolved in water, readily decomposes into nitrogen trifluoride|, Fluoronium|, and oxygen gas. Some hydrogen peroxide () is also formed during this process: : + → + + : + 2 → + + Reaction of with alkali metal nitrates yields fluorine nitrate, . ==Properties==

Because salts are destroyed by water, water cannot be used as a solvent. Instead, bromine trifluoride, bromine pentafluoride, iodine pentafluoride, or anhydrous hydrogen fluoride can be used. Tetrafluoroammonium salts usually have no colour. However, some are coloured due to other elements in them. , and have a red colour, while , , and are yellow. == Applications ==

salts are important for solid propellant gas generators. They are also used as reagents for electrophilic fluorination of aromatic compounds in organic chemistry. As fluorinating agents, they are also strong enough to react with methane. == See also ==