FeCl 2 finds some use as a reagent in organic synthesis. It is the precursor to hydrated iron(III) oxides that are magnetic pigments.
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It is used as a precursor to make various grades of hematite that can be used in a variety of pigments. It is used for odor control in wastewater treatment. Aside from use in the laboratory synthesis of iron complexes, ferrous chloride serves as a coagulation and flocculation agent in wastewater treatment, especially for wastes containing chromate or sulfides. Unlike the related ferrous sulfate and ferric chloride, ferrous chloride has few commercial applications. FeCl 2 is used to generate NHC complexes in situ for cross coupling reactions. The anhydrous FeCl 2, which is soluble in THF, is a standard precursor in organometallic synthesis. For example, solutions of the hydrates react with two molar equivalents of Cl to give the salt 2. įeCl 2 and its hydrates form complexes with many ligands. Tetra(pyridine)iron dichloride is prepared by treating ferrous chloride with pyridine. The octahedron is completed by a pair of mutually trans aquo ligands.
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Each Fe center is coordinated to four doubly bridging chloride ligands. The dihydrate, FeCl 2(H 2O) 2, crystallizes from concentrated hydrochloric acid. Ferric chloride decomposes to ferrous chloride at high temperatures. In one of two classic syntheses of ferrocene, Wilkinson generated FeCl 2 in situ by comproportionation of FeCl 3 with iron powder in tetrahydrofuran (THF). The net reaction is shown:įeBr 2 and FeI 2 can be prepared analogously.Īn alternative synthesis of anhydrous ferrous chloride is the reduction of FeCl 3 with chlorobenzene: 2 FeCl 3 + C 6H 5Cl → 2 FeCl 2 + C 6H 4Cl 2 + HCl This reaction gives the methanol solvate of the dichloride, which upon heating in a vacuum at about 160 ☌ converts to anhydrous FeCl 2. Anhydrous FeCl 2 įerrous chloride is prepared by addition of iron powder to a solution of hydrochloric acid in methanol. It is also a byproduct from titanium production, since some titanium ores contain iron. Ferrous chloride can also be used to regenerate hydrochloric acid. Ferrous chloride is used in the manufacturing of ferric chloride.
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The spent acid requires treatment if it is disposed. Such solutions are designated "spent acid," or "pickle liquor" especially when the hydrochloric acid is not completely consumed: Hydrated forms of ferrous chloride are generated by treatment of wastes from steel production with hydrochloric acid. Structure of "FeCl 2(thf) x", Fe 4Cl 8(thf) 6, illustrating both tetrahedral and octahedral coordination geometries.