|Jmol-3D images||Image 1|
|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) 
|Boiling point||1023 °C (anhydrous)|
|Solubility in water||64.4 g/100 mL (10 °C),
68.5 g/100mL (20 °C),
105.7 g/100 mL (100 °C)
|Solubility in THF||soluble|
|Solubility in ethanol||100 g/100 mL|
|octahedral at Fe|
|Other anions||Iron(II) fluoride
|Other cations||Cobalt(II) chloride
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point, and is 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. The compound is also soluble in water; aqueous solutions of FeCl2 are yellow.
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:
Ferrous chloride is conveniently prepared by addition of iron powder to a solution of methanol and concentrated hydrochloric acid under an inert atmosphere. This reaction gives the methanol solvate, which upon heating in a vacuum at about 160 °C gives anhydrous FeCl2. FeBr2 and FeI2 can be prepared analogously.
- 2 FeCl3 + C6H5Cl → 2 FeCl2 + C6H4Cl2 + HCl
FeCl2 prepared in this way exhibits convenient solubility in tetrahydrofuran (THF), a common solvent for chemical reactions. In one of two classic syntheses of ferrocene, Wilkinson generated FeCl2 by heating FeCl3 with iron powder in THF. Ferric chloride decomposes to ferrous chloride at high temperatures.
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.
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. Ferrous chloride is employed as a reducing agent in many organic synthesis reactions.
- Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
- 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; Thompson, D. W.; Loehe, J. R. (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", Org. Synth.; Coll. Vol. 4: 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.