Iron(II) fluoride
| Iron(II) fluoride | |
|---|---|
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| Identifiers | |
| CAS number | 7789-28-8  = ?, 13940-89-1 (tetrahydrate) |
| PubChem | 522690 |
| ChemSpider | 74215  |
| Jmol-3D images | {{#if:[Fe+2].[F-].[F-]|Image 1 |
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| Properties | |
| Molecular formula | FeF2 |
| Molar mass | 93.84 g/mol (anhydrous) 165.k90 g/mol (tetrahydrate) |
| Appearance | red-violet transparent crystal |
| 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 | 165 g/100 mL |
| Solubility | 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 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 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]
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 anomaly occurred. This thermal anomaly 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 ± 0.23 kcal. mole−1.[7] The following reaction was proposed 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 ± 0.07 Å
- d2(Fe-F): 2.10 ± 0.04 Å
- d (F-F): 2.59 ± 0.13 Å
External links
References
- ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
- ↑ 2.0 2.1 Sigma-Aldrich. "Material Safety Data Sheet". Sigma-Aldrich. Retrieved 5 April 2011.
- ↑ 3.0 3.1 Iron (II) Fluoride in the Chembok site. Accessed on 2011-01-16.
- ↑ 4.0 4.1 4.2 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- ↑ 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.
- ↑ 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.
- ↑ 7.0 7.1 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.
- ↑ Ksp solubility constant for common salts. Solubility of things site. Accessed on 2011-01-16.
- ↑ 9.0 9.1 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.
- ↑ 10.0 10.1 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.
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