Dinitrogen difluoride

Dinitrogen difluoride^[1]
cis-dinitrogen difluoride	trans-dinitrogen difluoride
Names
	IUPAC name cis- or trans-dinitrogen difluoride
	Other names cis- or trans-difluorodiazene
Identifiers
CAS Number	13812-43-6 (cis) ; 13776-62-0 (trans);
3D model (JSmol)	(cis): Interactive image; (trans): Interactive image;
ChemSpider	10326121 (cis) ; 4516471 (trans) ;
PubChem CID	5364290 (cis); 5462838 (trans);
	InChI (cis): InChI=1S/F2N2/c1-3-4-2/b4-3- Key: DUQAODNTUBJRGF-ONEGZZNKBY; (trans): InChI=1/F2N2/c1-3-4-2/b4-3+ Key: DUQAODNTUBJRGF-ONEGZZNKBY; InChI=1S/F2N2/c1-3-4-2/b4-3+ Key: DUQAODNTUBJRGF-ARJAWSKDSA-N ;
	SMILES (cis): F\N=N\F; (trans): F\N=N/F;
Properties
Chemical formula	FN=NF
Molar mass	66.011 g·mol−1
Appearance	Colorless gas
Density	2.698 g/L
Melting point	cis: less than −195 °C (−319.0 °F; 78.1 K) ; trans: −172 °C (−278 °F)
Boiling point	cis: −105.75 °C (−158.35 °F; 167.40 K) ; trans: −111.45 °C (−168.61 °F)
Dipole moment	cis: 0.16 D; trans: 0 D
Thermochemistry
Std enthalpy of; formation (ΔfH⦵298)	cis: 69.5 kJ/mol; trans: 82.0 kJ/mol
Related compounds
Other anions	Azide
Other cations	Ammonium; Diazonium compounds; Pentazenium; Tetrafluoroammonium;
Related compounds	Azo compounds; Diazene; Triazene; Tetrazene; Nitrogen trifluoride; Tetrafluorohydrazine;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) 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 fluorine azide (FN₃). It has the structure F−N=N−F and exists in both cis and trans isomers, as typical for diimides.

Isomers

The cis isomer has C_2v symmetry and the trans isomer has C_2h symmetry. These isomers can interconvert, but the process is slow enough at low temperature that the two can separated by low-temperature fractionation.^{[clarification needed]} The trans isomer is less thermodynamically stable^[2] but can be stored in glass vessels. The cis isomer attacks glass over a time scale of about 2 weeks to form silicon tetrafluoride and nitrous oxide:^[3]^{[page needed]}

2 N₂F₂ + SiO₂ → SiF₄ + 2 N₂O

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.^[4]

Difluoramine forms a solid unstable compound with potassium fluoride (or rubidium fluoride or caesium fluoride) which decomposes to dinitrogen difluoride.^[4]

It can also be prepared by photolysis of tetrafluorohydrazine and bromine:^[5]

N₂F₄ N₂F₂ + byproducts

Reactions

The cis form of difluorodiazene will react with strong fluoride ion acceptors such as antimony pentafluoride to form the linear^[6] [N≡N−F]⁺ cation (fluorodiazonium cation^[6]) which forms a salt with the formula [N≡N−F]⁺[SbF₆]⁻ (fluorodiazonium hexafluoroantimonate(V)).

F−N=N−F + SbF₅ → [N≡N−F]⁺[SbF₆]⁻

Analogous reaction of cis-difluorodiazene with arsenic pentafluoride gives white solid salt with the formula [N≡N−F]⁺[AsF₆]⁻^[6] (fluorodiazonium hexafluoroarsenate(V)).

F−N=N−F + AsF₅ → [N≡N−F]⁺[AsF₆]⁻

In the solid phase, the observed N≡N and N−F bond distances in the [N≡N−F]⁺ cation are 1.089(9) and 1.257(8) Å respectively, among the shortest experimentally observed N-N and N-F bonds.

References

^ Lide, David R. (1998). Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. pp. 4–73, 5–15, 9–46. ISBN 0-8493-0594-2.
^ Christe, Karl O.; Dixon, David A.; Grant, Daniel J.; Haiges, Ralf; Tham, Fook S.; Vij, Ashwani; Vij, Vandana; Wang, Tsang-Hsiu; Wilson, William W. (2010-08-02). "Dinitrogen Difluoride Chemistry. Improved Syntheses of cis - and trans -N 2 F 2 , Synthesis and Characterization of N 2 F + Sn 2 F 9 − , Ordered Crystal Structure of N 2 F + Sb 2 F 11 − , High-Level Electronic Structure Calculations of cis -N 2 F 2 , trans -N 2 F 2 , F 2 N═N, and N 2 F + , and Mechanism of the trans−cis Isomerization of N 2 F 2". Inorganic Chemistry. 49 (15): 6823–6833. doi:10.1021/ic100471s. ISSN 0020-1669. PMID 20465274.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
^ ^a ^b Sykes, A. G. (1989-07-17). Advances in Inorganic Chemistry. Academic Press. p. 171. ISBN 9780080578828. Retrieved 21 June 2014.
^ Leon M. Zaborowski; et al. (1973), Aaron Wold and John K. Ruff (ed.), Chlorodifluoroamine and Difluorodiazene - B. Difluorodiazene (Dinitrogen difluoride), Inorganic Syntheses (in German), vol. 14, McGraw-Hill Book Company, Inc., pp. 34–39
^ ^a ^b ^c Cacace, Fulvio; Grandinetti, Felice; Pepi, Federico (1995). "Gaseous Fluorodiazonium Ions. Experimental and Theoretical Study on Formation and Structure of FN2+". Inorganic Chemistry. 34 (6): 1325–1332. doi:10.1021/ic00110a007.

[hand-1] Lide, David R. (1998). Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. pp. 4–73, 5–15, 9–46. ISBN 0-8493-0594-2.

[2] Christe, Karl O.; Dixon, David A.; Grant, Daniel J.; Haiges, Ralf; Tham, Fook S.; Vij, Ashwani; Vij, Vandana; Wang, Tsang-Hsiu; Wilson, William W. (2010-08-02). "Dinitrogen Difluoride Chemistry. Improved Syntheses of cis - and trans -N 2 F 2 , Synthesis and Characterization of N 2 F + Sn 2 F 9 − , Ordered Crystal Structure of N 2 F + Sb 2 F 11 − , High-Level Electronic Structure Calculations of cis -N 2 F 2 , trans -N 2 F 2 , F 2 N═N, and N 2 F + , and Mechanism of the trans−cis Isomerization of N 2 F 2". Inorganic Chemistry. 49 (15): 6823–6833. doi:10.1021/ic100471s. ISSN 0020-1669. PMID 20465274.

[3] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[Sykes1989-4] Sykes, A. G. (1989-07-17). Advances in Inorganic Chemistry. Academic Press. p. 171. ISBN 9780080578828. Retrieved 21 June 2014.

[IS14-5] Leon M. Zaborowski; et al. (1973), Aaron Wold and John K. Ruff (ed.), Chlorodifluoroamine and Difluorodiazene - B. Difluorodiazene (Dinitrogen difluoride), Inorganic Syntheses (in German), vol. 14, McGraw-Hill Book Company, Inc., pp. 34–39

[pubs-6] Cacace, Fulvio; Grandinetti, Felice; Pepi, Federico (1995). "Gaseous Fluorodiazonium Ions. Experimental and Theoretical Study on Formation and Structure of FN2+". Inorganic Chemistry. 34 (6): 1325–1332. doi:10.1021/ic00110a007.

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