Chromium(II) fluoride

Chromium(II) fluoride

  Cr2+   F−
Names
Other names
chromium difluoride, chromium fluouride, chromous fluoride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.140 Edit this at Wikidata
EC Number
  • 233-168-0
UNII
  • InChI=1S/Cr.2FH/h;2*1H/q+2;;/p-2
    Key: RNFYGEKNFJULJY-UHFFFAOYSA-L
  • [F-].[F-].[Cr+2]
Properties
CrF2
Molar mass 89.9929 g·mol−1
Appearance blue-green iridescent crystals[1]
hygroscopic, turns to Cr2O3 when heated in air[1]
Density 3.79 g/cm3[1]
Melting point 894 °C (1,641 °F; 1,167 K)[1]
Boiling point > 1,300 °C (2,370 °F; 1,570 K)[1]
76.7 g/100 mL
Structure
monoclinic[1]
Thermochemistry
-8.645 kJ/g (solid)
Hazards
GHS labelling:
GHS05: CorrosiveGHS07: Exclamation mark
Danger
H314
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Chromium(II) fluoride is an inorganic compound with the formula CrF2. It exists as a blue-green iridescent solid. Chromium(II) fluoride is sparingly soluble in water, almost insoluble in alcohol, and is soluble in boiling hydrochloric acid, but is not attacked by hot distilled sulfuric acid or nitric acid. Like other chromous compounds, chromium(II) fluoride is oxidized to chromium(III) oxide in air.[2]

Preparation and structure

The compound is prepared by passing anhydrous hydrogen fluoride over anhydrous chromium(II) chloride. The reaction will proceed at room temperature but is typically heated to 100-200 °C to ensure completion:[3]

CrCl2 + 2 HF → CrF2 + 2 HCl

Like many difluorides, CrF2 adopts a structure like rutile with octahedral molecular geometry about Cr(II) and trigonal geometry at F−. Two of the six Cr–F bonds are long at 2.43 Å, and four are short near 2.00 Å.[4] This distortion is a consequence of the Jahn–Teller effect that arises from the d4 electron configuration of the chromium(II) ion.[5]

See also

References

  1. ^ a b c d e f Perry, Dale L. (2011). Handbook of Inorganic Compounds, Second Edition. Boca Raton, Florida: CRC Press. p. 120. ISBN 978-1-43981462-8. Retrieved 2014-01-10.
  2. ^ Merck Index, 14 ed. entry 2245
  3. ^ Brauer, Georg, ed. (1963). Handbook of preparative inorganic chemistry. Volume 1. Translated by Scripta Technica, Inc.; Riley, Reed F. (2nd ed.). New York, N.Y.: Academic Press. p. 256. ISBN 978-0121266011.
  4. ^ Jack, K. H.; Maitland, R. "Crystal structures and interatomic bonding of chromous and chromic fluorides" Proceedings of the Chemical Society, London (1957), 232. doi:10.1039/PS9570000217
  5. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1021–1022. ISBN 978-0-08-037941-8.