Iron(II) fluoride

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Iron(II) fluoride
Rutile-unit-cell-3D-balls.png
Identifiers
7789-28-8 N
13940-89-1 (tetrahydrate) N
ChemSpider 74215 YesY
Jmol 3D model Interactive image
PubChem 522690
  • InChI=1S/2FH.Fe/h2*1H;/q;;+2/p-2 YesY
    Key: FZGIHSNZYGFUGM-UHFFFAOYSA-L YesY
  • InChI=1/2FH.Fe/h2*1H;/q;;+2/p-2
    Key: FZGIHSNZYGFUGM-NUQVWONBAX
  • [Fe+2].[F-].[F-]
Properties
FeF2
Molar mass 93.84 g/mol (anhydrous)
165.902 g/mol (tetrahydrate)
Appearance red-violet transparent crystal
Density 4.09 g/cm3 (anhydrous)
2.20 g/cm3 (tetrahydrate)
Melting point 970 °C (1,780 °F; 1,240 K) (anhydrous)
100 °C (tetrahydrate)[1]
Boiling point 1,100 °C (2,010 °F; 1,370 K) (anhydrous)
165 g/100 mL
Solubility insoluble in ethanol, ether;
dissolves in HF
Structure
Rutile (tetragonal), tP6
P42/mnm, No. 136
Vapor pressure {{{value}}}
Related compounds
Other anions
 iron(II) oxide, iron(II) chloride
Other cations
 manganese(II) fluoride, cobalt(II) fluoride
Related compounds
 iron(III) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Iron(II) fluoride (also ferrous fluoride) is the inorganic compound with formula FeF2. It is a green high-melting solid. The name iron(II) fluoride also applies to hydrates FeF2·4H2O.

Structure and physical properties

Like many difluorides, FeF2 adopts the TiO2 rutile structure wherein the iron centers are octahedrally and the fluoride ions three coordinate.[2][3] The Fe-F bond lengths are 2.03 and 2.10 Å.

Low temperature neutron diffraction studies show that the material is antiferromagnetic.[4] Heat capacity measurements reveal an event at 78.3 K corresponding to ordering of antiferromagnetic state.[5]

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 ± 0.23 kcal. mole−1.[6] The following reaction was proposed in order to calculate the atomization energy for Fe+:[6]

FeF2 + e → Fe+ + F2 (or 2F) + 2e

Synthesis and reactions

The anhydrous salt can be prepared by combining the elements.[3]

Recrystallization of the anhydrous solid from water[3] yields the colorless tetrahydrate, FeF2·4H2O, (CAS Number 13940-89-1). The latter can exists in two structures, or polymorphs. One form is rhombohedral and one is hexagonal, the former having a disordered[7] The tetrahydrate oxidizes in moist air to a hydrate of iron(III) fluoride, 2FeF3·9H2O.[7] The hydrate is poorly soluble in water, with a solubility product, Ksp, of 2.36 × 10−6.[8]

External links

References

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  1. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
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  3. ↑ 3.0 3.1 3.2 Lua error in package.lua at line 80: module 'strict' not found.
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  7. ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Ksp solubility constant for common salts. Solubility of things site. Accessed on 2011-01-16.
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