Dinitrogen difluoride

cis-Dinitrogen difluoride (left) and trans-Dinitrogen difluoride (right)[1]
IUPAC name cis- or trans-dinitrogen difluoride
Other names cis- or trans-difluorodiazine
Identifiers
CAS number	13812-43-6, (cis) [13776-62-0] (trans)
ChemSpider	4516471 Y
Jmol-3D images	Image 1 Image 2
SMILES cis: F/N=N\F trans: F\N=N\F F\N=N\F
InChI InChI=1S/F2N2/c1-3-4-2/b4-3+ Y Key: DUQAODNTUBJRGF-ONEGZZNKSA-N Y InChI=1/F2N2/c1-3-4-2/b4-3+ Key: DUQAODNTUBJRGF-ONEGZZNKBY
Properties
Molecular formula	N2F2
Molar mass	66.010 g/mol
Appearance	colorless gas
Density	2.698 g/L
Melting point	cis: < -195 °C trans: -172 °C
Boiling point	cis: -105.75 °C trans: -111.45 °C
Dipole moment	cis: 0.16 D trans: 0 D
Thermochemistry
Std enthalpy of formation ΔfHo298	cis: 69.5 kJ/mol trans: 82.0 kJ/mol
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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. 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:^[2]

2 N₂F₂ + SiO₂ → SiF₄ + 2 N₂O

Most preparations of dinitrogen difluoride give mixtures of the two isomers, but they can be prepared independently.

The cis form of dinitrogen difluoride will react with strong fluoride ion accepters such as antimony pentafluoride to form N₂F⁺ cation.

N₂F₂ + SbF₅ → N₂F⁺[SbF₆]^-

In the solid phase of N₂F⁺ compound, the observed N−N and N−F bond distances of 1.089(9) and 1.257(8) Å, respectively, are among the shortest experimentally observed N−N and N−F bonds

References

1. ^ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 4–73, 5–15, 9–46. ISBN 0-8493-0594-2. 
2. ^ N. N. Greenwood and A. Earnshaw, Chemistry of the Elements, 2006 Butterworth-Heinemann