Dinitrogen difluoride


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.

Isomers

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:

Preparation

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 which decomposes to dinitrogen difluoride.
It can also be prepared by photolysis of tetrafluorohydrazine and bromine:

Reactions

The cis form of dinitrogen difluoride will react with strong fluoride ion acceptors such as antimony pentafluoride to form the N2F+ cation.
In the solid phase, the observed N=N and N−F bond distances in the N2F+ cation are 1.089 and 1.257 Å respectively, among the shortest experimentally observed N−N and N−F bonds.