![]() ![]() The anhydrous material is a powerful dehydrating agent. Iron(III) fluoride has also been shown to catalyze chemoselective addition of cyanide to aldehydes to give the cyanohydrins. Other metal fluorides also catalyse similar reactions. Specifically the coupling of biaryl compounds are catalyzed by hydrated iron(II) fluoride complexes of N-heterocyclic carbene ligands. Some cross coupling reaction are catalyzed by ferric fluoride-based compounds. The primary commercial use of iron(III) fluoride in the production of ceramics. Generally a trihydrate, its chemistry is slightly more complex: FeF 4 However, hydrated form is known as the very rare fumarolic mineral topsøeite. Pure FeF 3 is not yet known among minerals. The hydrates crystallize from aqueous hydrofluoric acid. It also forms as a passivating film upon contact between iron (and steel) and hydrogen fluoride. More practically and like most metal fluorides, it is prepared by treating the corresponding chloride with hydrogen fluoride: FeCl 3 + 3 HF → FeF 3 + 3 HCl Preparation, occurrence, reactions Īnhydrous iron(III) fluoride is prepared by treating virtually any anhydrous iron compound with fluorine. The two forms are distinguished by their difference in quadrupole splitting from their Mössbauer spectra. The solid α form is unstable and converts to the β form within days. The space group of the β form is P4/m, and the α form maintains a P4/m space group with a J6 substructure. These are prepared by evaporation of an HF solution containing Fe 3+ at room temperature (α form) and above 50 ☌ (β form). Two crystalline forms-or more technically, polymorphs-of FeF 3♳H 2O are known, the α and β forms. At very high temperatures, it decomposes to give FeF 2 and F 2. Although the solid is nonvolatile, it evaporates at high temperatures, the gas at 987 ☌ consists of FeF 3, a planar molecule of D 3h symmetry with three equal Fe-F bonds, each of length 176.3 pm. The structural motif is similar to that seen in ReO 3. In the language of crystallography, the crystals are classified as rhombohedral with an R-3c space group. The anhydrous form adopts a simple structure with octahedral Fe(III)F 6 centres interconnected by linear Fe-F-Fe linkages. Both anhydrous iron(III) fluoride as well as its hydrates are hygroscopic. Iron(III) fluoride is a thermally robust, antiferromagnetic solid consisting of high spin Fe(III) centers, which is consistent with the pale colors of all forms of this material. Anhydrous iron(III) fluoride is white, whereas the hydrated forms are light pink. They are mainly of interest by researchers, unlike the related iron(III) chlorides. Iron(III) fluoride, also known as ferric fluoride, are inorganic compounds with the formula FeF 3(H 2O) x where x = 0 or 3. ![]()
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