Chromium(III) fluoride

Chromium(III) fluoride
Names
	IUPAC name Chromium(III) fluoride
Identifiers
CAS Number	7788-97-8 ; 16671-27-5 (trihydrate); 123333-98-2 (tetrahydrate);
3D model (JSmol)	Interactive image; Interactive image;
ChemSpider	8329529 ;
ECHA InfoCard	100.029.216
PubChem CID	10154021;
RTECS number	GB6125000;
CompTox Dashboard (EPA)	DTXSID10880971 ;
	InChI InChI=1S/Cr.3FH/h;31H/q+3;;;/p-3 Key: FTBATIJJKIIOTP-UHFFFAOYSA-K ; InChI=1/Cr.3FH/h;31H/q+2;;;/p-3 Key: FEQFRFOUOCAJNF-DFZHHIFOAC; InChI=1/Cr.3FH/h;3*1H/q+3;;;/p-3 Key: FTBATIJJKIIOTP-DFZHHIFOAR;
	SMILES [Cr+2].[F-].[F-].[F-]; [Cr+3].[F-].[F-].[F-];
Properties
Chemical 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 otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Chromium(III) fluoride is the name for the inorganic compounds with the 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

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

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

References

^ 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
^ 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
^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.

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[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

[Ullmann-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.

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