Krypton difluoride

Krypton difluoride
Skeletal formula of krypton difluoride with a dimension
Skeletal formula of krypton difluoride with a dimension
Spacefill model of krypton difluoride
Spacefill model of krypton difluoride
Names
IUPAC name
Krypton difluoride
Other names
Krypton fluoride
Krypton(II) fluoride
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/KrF2/c1-3-2 checkY
    Key: QGOSZQZQVQAYFS-UHFFFAOYSA-N checkY
  • InChI=1/F2Kr/c1-3-2
    Key: QGOSZQZQVQAYFS-UHFFFAOYAJ
  • F[Kr]F
Properties
F2Kr
Molar mass 121.795 g·mol−1
Appearance Colourless crystals (solid)
Density 3.24 g cm−3 (solid)
Reacts
Structure
Body-centered tetragonal[1]
P42/mnm, No. 136
a = 0.4585 nm, c = 0.5827 nm
Linear
0 D
Related compounds
Related compounds
Xenon difluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Krypton difluoride, KrF2 is a chemical compound of krypton and fluorine. It was the first compound of krypton discovered.[2] It is a volatile, colourless solid at room temperature. The structure of the KrF2 molecule is linear, with Kr−F distances of 188.9 pm. It reacts with strong Lewis acids to form salts of the KrF+ and Kr
2
F+
3
cations.[3]

The atomization energy of KrF2 (KrF2(g) → Kr(g) + 2 F(g)) is 21.9 kcal/mol, giving an average Kr–F bond energy of only 11 kcal/mol,[4] the weakest of any isolable fluoride. In comparison, the dissociation of difluorine to atomic fluorine requires cleaving a F–F bond with a bond dissociation energy of 36 kcal/mol. Consequently, KrF2 is a good source of the extremely reactive and oxidizing atomic fluorine. It is thermally unstable, with a decomposition rate of 10% per hour at room temperature.[5] The formation of krypton difluoride is endothermic, with a heat of formation (gas) of 14.4 ± 0.8 kcal/mol measured at 93 °C.[5]

  1. ^ R. D. Burbank, W. E. Falconer and W. A. Sunder (1972). "Crystal Structure of Krypton Difluoride at −80 °C". Science. 178 (4067): 1285–1286. doi:10.1126/science.178.4067.1285. PMID 17792123. S2CID 96692996.
  2. ^ Grosse, A. V.; Kirshenbaum, A. D.; Streng, A. G.; Streng, L. V. (1963). "Krypton Tetrafluoride: Preparation and Some Properties". Science. 139 (3559): 1047–8. Bibcode:1963Sci...139.1047G. doi:10.1126/science.139.3559.1047. PMID 17812982.
  3. ^ Cite error: The named reference Lehmann was invoked but never defined (see the help page).
  4. ^ The values of De(F–KrF) and De(F–Kr•) are estimated to be comparable, at ~10-12 kcal/mol, while ΔH(KrF+ → Kr+ + F•) is estimated to be ~42 kcal/mol.
  5. ^ a b Cockett, A. H.; Smith, K. C.; Bartlett, Neil (1973). The Chemistry of the Monatomic Gases: Pergamon Texts in Inorganic Chemistry. Pergamon Press. ISBN 978-0-08-018782-2.