trans-1,2-difluorodiazine

Dinitrogen difluoride is a chemical compound with the formula N2F2. It is a gas at room temperature, and was first identified in 1952 as the thermal decomposition product of the azide N3F. It has the structure F−N=N−F and exists in both a cis- and trans-form. The cis configuration lies in a C2v symmetry and the trans-form has a symmetry of C2h. These isomers are thermally interconvertible but can be separated by low temperature fractionation. The trans-form is less thermodynamically stable but can be stored in glass vessels. The cis-form attacks glass over a time scale of about 2 weeks to form silicon tetrafluoride and nitrous oxide:
2N2F2 + SiO2 → SiF4 + 2N2O
Most preparations of dinitrogen difluoride give mixtures of the two isomers, but they can be prepared independently.
An aqueous method involves N,N-difluorourea with concentrated potassium hydroxide. This gives a 40% yield with three times more of the trans isomer.
Difluoramine forms a solid unstable compound with potassium fluoride (or rubidium fluoride or caesium fluoride) which decomposes to dinitrogen difluoride.
The cis form of dinitrogen difluoride will react with strong fluoride ion acceptors such as antimony pentafluoride to form the N2F+ cation.
N2F2 + SbF5 → N2F+[SbF6]−
In the solid phase, the observed N=N and N−F bond distances in the N2F+ cation are 1.089(9) and 1.257(8)Å respectively, among the shortest experimentally observed N−N and N−F bonds.