Nitride fluorides containing nitride and fluoride ions with the formula NF<sup>4-</sup>. They can be electronically equivalent to a pair of oxide ions O<sub>2</sub><sup>4-</sup>. Nitride fluorides were discovered in 1996 by Lavalle et al. They heated diammonium technetium hexafluoride to 300 ðC to yield TcNF. Another preparation is to heat a fluoride compound with a nitride compound in a solid state reaction. The fluorimido ion is F-N<sup>2-</sup> and is found in a rhenium compound.