Iron(II) fluoride

Iron(II) fluoride
Identifiers
CAS number 7789-28-8, 
13940-89-1 (tetrahydrate)
PubChem 522690
ChemSpider 74215 Y
Jmol-3D images Image 1
Properties
Molecular formula FeF2
Molar mass 93.84 g/mol (anhydrous)
165.k90 g/mol (tetrahydrate)
Appearance white crystalline solid
Density 4.09 g/cm3 (anhydrous)
2.20 g/cm3 (tetrahydrate)
Melting point

970 °C (anhydrous)
100 °C (tetrahydrate) [1]
Boiling point

1100 °C (anhydrous)
Solubility in water insoluble in ethanol, ether;
dissolves in HF
Structure
Crystal structure Rutile (tetragonal), tP6
Space group P42/mnm, No. 136
Hazards
Main hazards Causes severe skin burns & eye damage;
Hazardous decomposition products formed under fire conditions- Iron oxides [2]
Flash point not applicable [2]
Related compounds
Other anions iron(II) oxide, iron(II) chloride
Other cations manganese(II) fluoride, cobalt(II) fluoride
Related compounds iron(III) fluoride
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Iron(II) fluoride (also ferrous fluoride) is a chemical compound with formula FeF2. It is a green crystalline solid that melts at about 1000°C.[3] It is used in ceramics and as a catalyst in some organic reactions.[3]

The anhydrous salt can be prepared by reacting the elements.[4] It has the TiO2 rutile structure where the iron atoms are octahedrally coordinated and the fluoride ions three coordinate.[4]

Contents

Physical Properties

Through neutron diffraction studies at low temperatures, Iron(II) fluoride is antiferromagnetic.[5] Heat capacity was measured over a temperature range 12-300 K. At temperature 78.3 K a thermal anomalie occurred. This thermal anomalie can be explained as Iron(II) fluoride passing from its disordered paramagnetic state to a more ordered antiferromagnetic state.[6]

The vapor species were identified between 965 and 1149 K. Using mass spectrometry the heat of sublimation was experimentally determined and averaged to be 75.56 ± 0.23kcal. mole−1.[7] The following reaction was propsed in order to calculate the atomization energy for Fe+:

FeF2 + e → Fe+ +F2(or 2F) + 2e [7]

Crystal Structure

It is slightly soluble in water[4] (Ksp = 2.36 × 10−6)[8] and can be crystallized from it as a colorless tetrahydrate, FeF2·4H2O, (CAS Number 13940-89-1). The latter exists in two crystal structures, one rhombohedral and one hexagonal, the former having a disordered [9] The tetrahydrate oxidizes in moist air to a hydrate of iron(III) fluoride, 2FeF3·9H2O.[9]

To determine impurities in previous crystal structuring of the FeF2 the compound was first melted and then through spectrochemical analysis the percent of impurities could be determined.[10]

Though calculations using the lattice constants, found through X-ray crystallography, the bond lengths[10] were determined as follows:

d1(Fe-F): 2.03± 0.07Å
d2(Fe-F): 2.10± 0.04Å
d (F-F): 2.59± 0.13Å

External links

References

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
  2. ^ a b Sigma-Aldrich. "Material Safety Data Sheet". Sigma-Aldrich. http://www.sigmaaldrich.com/catalog/DisplayMSDSContent.do. Retrieved 5 April 2011. 
  3. ^ a b Iron (II) Fluoride in the Chembok site. Accessed on 2011-01-16.
  4. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
  5. ^ Erickson, R (June 1953). "Neutron Diffraction Studies of Antiferromagnetism in Manganous Fluoride and Some Isomorphous Compounds". Physical Review 90 (5): 779–785. doi:10.1103/PhysRev.90.779. http://link.aps.org/doi/10.1103/PhysRev.90.779. 
  6. ^ Stout, J; Edward Catalano (December 1953). "Thermal Anomalies Associated with the Antiferromagnetic Ordering of FeF2, CoF3, and NiF2". Physical Review 92 (6): 1575–1575. doi:10.1103/PhysRev.92.1575. http://link.aps.org/doi/10.1103/PhysRev.92.1575. 
  7. ^ a b Kent, Richard; John L. Margrave (November 1965). "Mass Spectometric at High Temperatures. VIII. The Sublimation Pressure of Iron(II) Fluoride". Journal of the American Chemical Society 87 (21): 4754–4756. 
  8. ^ Ksp solubility constant for common salts. Solubility of things site. Accessed on 2011-01-16.
  9. ^ a b Penfold, B. R.; Taylor, M. R. (1960). "The crystal structure of a disordered form of iron(II) fluoride tetrahydrate". Acta Crystallographica 13: 953–956. doi:10.1107/S0365110X60002302. 
  10. ^ a b Stout, J.; Stanley A. Reed (Nov. 5, 1954). "The Crystal Structure of MnF2, FeF2, CoF2, NiF2 and ZnF2". Crystal Structures of Anhydrous Fluorides: 5279–5281.