Chromium trifluoride

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Chromium trifluoride
Aluminium-trifluoride-3D-polyhedra.png
FeF3structure.jpg
Identifiers
CAS number 7788-97-8 YesY, 16671-27-5 (trihydrate), 123333-98-2 (tetrahydrate)
PubChem 10154021
ChemSpider 8329529 YesY
RTECS number GB6125000
Jmol-3D images Image 1
Image 2
Properties
Molecular formula CrF3
Molar mass 108.9913 g/mol (anhydrous)
163.037 g/mol (trihydrate)
181.05 g/mol (tetrahydrate)
Appearance green crystalline solid
Density 3.8 g/cm3 (anhydrous)
2.2 g/cm3 (trihydrate)
Melting point 1100 °C (sublimes)
Solubility in water negligible (anhydrous)
sparingly soluble (trihydrate)
Solubility insoluble and alcohols
soluble in HF, HCl
Structure
Crystal structure Rhombohedral, hR24
Space group R-3c, No. 167
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Chromium(III) fluoride is the name for the inorganic compounds with the chemical formula CrF3 as well as several related hydrates. The compound CrF3 is a green crystalline solid that is insoluble in common solvents, but the coloured hydrates [Cr(H2O)6]F3 and [Cr(H2O)6]F3·3H2O are soluble in water. The trihydrate is green, and the hexahydrate is violet. The anhydrous form sublimes at 1100–1200 °C. Like almost all compounds of chromium(III), these compounds feature octahedral Cr centres. In the anhydrous form, the six coordination sites are occupied by fluoride ligands that bridge to adjacent Cr centres. In the hydrates, some or all of the fluoride ligands are replaced by water.[1]

Production[edit]

Chromium(III) fluoride is produced from the reaction of chromium(III) oxide and hydrofluoric acid:[2]

Cr2O3 + 6 HF + 9 H2O → 2 [Cr(H2O)6]F3

The anhydrous form is produced from hydrogen fluoride and chromic chloride:[3]

CrCl3 + 3 HF → CrF3 + 3 HCl

Uses[edit]

Chromium(III) fluoride is not heavily used, but finds some applications as a mordant in textiles and as a corrosion inhibitor.

References[edit]

  1. ^ F.H. Herbstein, M. Kapon and G.M. Reisner, "Crystal structures of chromium(III) fluoride trihydrate. Structural chemistry of hydrated transition metal fluorides. Thermal decomposition of chromium(III) fluoride nonhydrate" Zeitschrift für Kristallographie 1985, volume 171, pp. 209
  2. ^ Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger, "Chromium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.doi:10.1002/14356007.a07_067
  3. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.