Английская Википедия:Iron(II) fluoride

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Шаблон:Chembox Iron(II) fluoride or ferrous fluoride is an inorganic compound with the molecular formula FeF2. It forms a tetrahydrate FeF2·4H2O that is often referred to by the same names. The anhydrous and hydrated forms are white crystalline solids.[1][2]

Structure and bonding

Anhydrous FeF2 adopts the TiO2 rutile structure. As such, the iron cations are octahedral and fluoride anions are trigonal planar.[3][4]

The tetrahydrate can exist in two structures, or polymorphs. One form is rhombohedral and the other is hexagonal, the former having a disorder.[1]

Like most fluoride compounds, the anhydrous and hydrated forms of iron(II) fluoride feature high spin metal center. Low temperature neutron diffraction studies show that the FeF2 is antiferromagnetic.[5] Heat capacity measurements reveal an event at 78.3 K corresponding to ordering of antiferromagnetic state.[6]

Selected physical properties

FeF2 sublimes between 958 and 1178 K. Using Torsion and Knudsen methods, the heat of sublimation was experimentally determined and averaged to be 271 ± 2 kJ mole−1.[7]

The following reaction is proposed in order to calculate the atomization energy for Fe+:[8]

FeF2 + e → Fe+ + F2 (or 2F) + 2e

Synthesis and reactions

The anhydrous salt can be prepared by reaction of ferrous chloride with anhydrous hydrogen fluoride.[9] It is slightly soluble in water (with solubility product Ksp = 2.36×10−6 at 25 °C)[10] as well as dilute hydrofluoric acid, giving a pale green solution.[1] It is insoluble in organic solvents.[2]

The tetrahydrate can be prepared by dissolving iron in warm hydrated hydrofluoric acid and precipitating the result by addition of ethanol.[1] It oxidizes in moist air to give, inter alia, a hydrate of iron(III) fluoride, (FeF3)2·9H2O.[1]

Uses

FeF2 is used to catalyze some organic reactions.[11]

References

Шаблон:Reflist

External links

Шаблон:Iron compounds Шаблон:Fluorides

  1. 1,0 1,1 1,2 1,3 1,4 Шаблон:Cite journal
  2. 2,0 2,1 Dale L. Perry (1995), "Handbook of Inorganic Compounds", page 167. CRC Press. Шаблон:ISBN
  3. Шаблон:Cite journal
  4. Шаблон:Cite journal
  5. Шаблон:Cite journal
  6. Шаблон:Cite journal
  7. Шаблон:Cite journal
  8. Шаблон:Cite journal
  9. W. Kwasnik "Iron(II) Fluoride" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 266.
  10. Шаблон:Cite web
  11. Шаблон:Ullmann