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| Names | |
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| Other names iron trifluoride, ferric fluoride | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.029.093 |
| RTECS number |
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| UNII | |
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| Properties | |
| FeF3 | |
| Molar mass | 112.840 g/mol (anhydrous) 166.89 g/mol (trihydrate) |
| Appearance | pale green crystals |
| Density | 3.87 g/cm3 (anhydrous) 2.3 g/cm3 (trihydrate) |
| Melting point | > 1,000 °C (1,830 °F; 1,270 K) |
| slightly soluble (anhydrous) 49.5 g/100 mL (trihydrate) | |
| Solubility | negligible inalcohol,ether,benzene |
| +13,760·10−6 cm3/mol | |
| Structure | |
| Rhombohedral,hR24 | |
| R-3c, No. 167 | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Corrosive |
| GHS labelling: | |
  [1] | |
| Danger[1] | |
| H302,H312,H314,H332[1] | |
| P260,P301+P330+P331,P303+P361+P353,P305+P351+P338,P405,P501[1] | |
| Safety data sheet (SDS) | External SDS |
| Related compounds | |
Otheranions | Iron(III) oxide,Iron(III) chloride |
Othercations | Manganese(III) fluoride,Cobalt(III) fluoride,Ruthenium(III) fluoride |
Related compounds | Iron(II) fluoride |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Iron(III) fluoride, also known as ferric fluoride, areinorganic compounds with the formula FeF3(H2O)x where x = 0 or 3. They are mainly of interest by researchers, unlike the relatediron(III) chloride. Anhydrous iron(III) fluoride is white, whereas the hydrated forms are light pink.[2]
Iron(III) fluoride is a thermally robust,antiferromagnetic[3] solid consisting ofhigh spin Fe(III) centers, which is consistent with the pale colors of all forms of this material. Both anhydrous iron(III) fluoride as well as its hydrates arehygroscopic.
The anhydrous form adopts a simple structure withoctahedral Fe(III)F6 centres interconnected by linear Fe-F-Fe linkages. In the language ofcrystallography, the crystals are classified as rhombohedral with an R-3cspace group.[4] The structural motif is similar to that seen inReO3. Although the solid is nonvolatile, it evaporates at high temperatures, the gas at 987 °C consists of FeF3, a planar molecule of D3hsymmetry with three equal Fe-F bonds, each of length 176.3 pm.[5] At very high temperatures, it decomposes to give FeF2 and F2.[4]
Two crystalline forms—or more technically,polymorphs—of FeF3·3H2O are known, the α and β forms. These are prepared by evaporation of anHF solution containing Fe3+ at room temperature (α form) and above 50 °C (β form). Thespace group of the β form is P4/m, and the α form maintains a P4/m space group with a J6 substructure. The solid α form is unstable and converts to the β form within days. The two forms are distinguished by their difference in quadrupole splitting from theirMössbauer spectra.[6]
Anhydrous iron(III) fluoride is prepared by treating virtually any anhydrous iron compound with fluorine. More practically and like most metal fluorides, it is prepared by treating the correspondingchloride with hydrogen fluoride:[7]
It also forms as a passivating film upon contact between iron (and steel) andhydrogen fluoride.[8] The hydrates crystallize from aqueous hydrofluoric acid.[6]
The material is a fluoride acceptor. Withxenon hexafluoride it forms [XeF5]+[FeF4]−.[4]
Pure FeF3 is not yet known among minerals. However, hydrated form is known as the very rarefumarolic mineral topsøeite. Generally a trihydrate, its chemistry is slightly more complex: FeF[F0.5(H2O)0.5]4·H2O.[9][10]
The primary commercial use of iron(III) fluoride in the production of ceramics.[11]
Somecross coupling reaction are catalyzed by ferric fluoride-based compounds. Specifically the coupling of biaryl compounds are catalyzed by hydrated iron(II) fluoride complexes ofN-heterocyclic carbene ligands. Other metal fluorides alsocatalyse similar reactions.[12][13] Iron(III) fluoride has also been shown to catalyze chemoselective addition of cyanide to aldehydes to give thecyanohydrins.[14]
The anhydrous material is a powerful dehydrating agent. The formation of ferric fluoride may have been responsible for the explosion of a cylinder of hydrogen fluoride gas.[15]
