Chromium(III) fluoride

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Chromium(III) fluoride
Names
IUPAC name
Chromium(III) fluoride
Other names
Chromium trifluoride
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.029.216 Edit this at Wikidata
RTECS number
  • GB6125000
UNII
  • InChI=1S/Cr.3FH/h;3*1H/q+3;;;/p-3 checkY
    Key: FTBATIJJKIIOTP-UHFFFAOYSA-K checkY
  • InChI=1/Cr.3FH/h;3*1H/q+3;;;/p-3
    Key: FTBATIJJKIIOTP-DFZHHIFOAR
  • [Cr+3].[F-].[F-].[F-]
Properties
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 1,100 °C (2,010 °F; 1,370 K) (sublimes)
negligible (anhydrous)
sparingly soluble (trihydrate)
Solubility Insoluble in
alcohols
Soluble in HF, HCl
+4370.0·10−6 cm3/mol
Structure
Rhombohedral, hR24
R-3c, No. 167
Hazards
Lethal dose or concentration (LD, LC):
150 mg/kg (guinea pig, oral)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 mg/m3[1]
REL (Recommended)
 TWA 0.5 mg/m3[1]
IDLH
(Immediate danger)
 250 mg/m3[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Chromium(III) fluoride is an

sublimes at 1100–1200 °C.[3]

Structures

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.[4]

Production

Chromium(III) fluoride is produced from the reaction of chromium(III) oxide and hydrofluoric acid:[5]

Cr2O3 + 6 HF + 9 H2O → 2 [Cr(H2O)6]F3

The anhydrous form is produced from

chromic chloride:[6]

CrCl3 + 3 HF → CrF3 + 3 HCl

Another method of synthesis of CrF3 involves thermal decomposition of [NH4]3[CrF6] (ammonium hexafluorochromate(III)):

[NH4]3[CrF6] → CrF3 + 3 NH3 + 3 HF

A mixed valence compound Cr2F5 (chromium(II,III) fluoride) is also known.[7]

Uses

Chromium(III) fluoride finds some applications as a

chlorocarbons by HF.[8][9]

References

  1. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ "Chromium(III) compounds [as Cr(III)]". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. ISBN 978-0-08-037941-8
    .
  4. ^ 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
  5. doi:10.1002/14356007.a07_067
  6. ISBN 0-7506-3365-4
    .
  7. ^ Sturm. B.J. Phase Equilibria in the System Chromium(II)Fluoride-Chromium(III) Fluoride. Inorg. Chem., 1962, 1 (3), pp 665–672
  8. ^ Mallikarjuna R. V. N.; Subramanian M. A. Fluoroolefin Manufacturing U.S. Patent 6,031,14, August 6, 1998; n.a.
  9. ^ Ruh R. P.; Davis R. A. Proceess for Fluorinating Aliphatic Halohydrocarbons with a Chromium Fluoride catalyst and process for preparing the catalyst. U.S. Patent 2,745,886, May 15, 1956; n.a.
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