Iron(II) chloride
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| Names | |
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| IUPAC names
Iron(II) chloride
Iron dichloride | |
| Other names
Ferrous chloride,
Rokühnite | |
| Identifiers | |
| ECHA InfoCard | 100.028.949 |
PubChem CID
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| RTECS number |
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CompTox Dashboard (EPA)
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| Properties | |
| FeCl2 | |
| Molar mass | 126.751 g/mol (anhydrous) 198.8102 g/mol (tetrahydrate) |
| Appearance | tan solid (anhydrous) pale green solid (di-tetrahydrate) |
| Density | 3.16 g/cm3 (anhydrous) 2.30 g/cm3 (dihydrate) 1.39 g/cm3 (tetrahydrate) |
| Melting point | 677 °C (anhydrous) 120 °C (dihydrate) 105 °C (tetrahydrate) [1] |
| Boiling point | 1023 °C (anhydrous) |
| 64.4 g/100 mL (10°C), 68.5 g/100mL (20°C), 105.7 g/100 mL (100°C) | |
| Solubility in THF | soluble |
| Structure | |
| Monoclinic | |
| octahedral at Fe | |
| Related compounds | |
Other anions
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Iron(II) fluoride Iron(II) bromide Iron(II) iodide |
Other cations
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Cobalt(II) chloride Manganese(II) chloride Copper(II) chloride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It has a high melting point, paramagnetic solid, usually obtained as an off-white solid. FeCl2 crystallizes from water as the greenish tetrahydrate, which is the form that is most commonly encountered in commerce and the laboratory. There is also a dihydrate.
Production
Hydrated forms of ferrous chloride are generated by treatment of wastes from steel production with hydrochloric acid. Such solutions are designated "spent acid," especially when the hydrochloric acid is not completely consumed:
The spent acid requires treatment before its disposal. It is also byproduct from titanium production, since some titanium ores contain iron.[2]
Laboratory preparation
Ferrous chloride is conveniently prepared using a methanol solution of concentrated hydrochloric acid. This reaction gives the methanol solvate, which upon heating in a vacuum at about 160 °C gives anhydrous FeCl2.[3] FeBr2 and FeI2 can be prepared analogously.
An alternative laboratory synthesis of FeCl2 entails the reaction of FeCl3 with chlorobenzene:[4]
- 2 FeCl3 + C6H5Cl → 2 FeCl2 + C6H4Cl2 + HCl
FeCl2 prepared in this way exhibits convenient solubility in tetrahydrofuran, a common solvent for chemical reactions. In one of two classic syntheses of ferrocene, Wilkinson generated FeCl2 by heating FeCl3 with iron powder.[5] Ferric chloride decomposes to ferrous chloride at high temperatures.
Reactions
FeCl2 forms complexes with many ligands. It reacts with two molar equivalents of [(C2H5)4N]Cl to give the salt [(C2H5)4N]2[FeCl4]. Related compounds that can be prepared similarly include the [MnCl4]2−, [MnBr4]2−, [MnI4]2−, [FeBr4]2−, [CoCl4]2−, [CoBr4]2−, [NiCl4]2−, and [CuCl4]2− salts.[6]
Applications
Ferrous chloride has a variety of niche applications, but the related compounds ferrous sulfate and ferric chloride enjoy more applications. Aside from use in the laboratory synthesis of iron complexes, ferrous chloride serves as a reducing flocculating agent in wastewater treatment, especially for wastes containing chromate. It is the precursor to hydrated iron(III) oxides that are magnetic pigments.[2] Ferrous chloride employed as a reducing agent in organic synthesis.
References
- ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
- ^ a b Egon Wildermuth, Hans Stark, Gabriele Friedrich, Franz Ludwig Ebenhöch, Brigitte Kühborth, Jack Silver, Rafael Rituper “Iron Compounds” in Ullmann’s Encyclopedia of Industrial Chemistry Wiley-VCH, Wienheim, 2005.
- ^ G. Winter (1973). "Iron(II) Halides". Inorg. Synth. 14: 99–104. doi:10.1002/9780470132456.ch20.
- ^ P. Kovacic and N. O. Brace (1960). "Iron(II) Chloride". Inorg. Synth. 6: 172. doi:10.1002/9780470132371.ch54.
- ^ G. Wilkinson (1963). "Ferrocene". Organic Syntheses; Collected Volumes, vol. 4, p. 473.
- ^ N. S. Gill, F. B. Taylor (1967). "Tetrahalo Complexes of Dipositive Metals in the First Transition Series". Inorg. Synth. 9: 136–142. doi:10.1002/9780470132401.ch37.