Iron(II) chloride

Iron(II) chloride
Names
IUPAC names
Iron(II) chloride
Iron dichloride
Other names
Ferrous chloride,
Rokühnite
Identifiers
ATC code B03AA05
7758-94-3 Yes
16399-77-2 (dihydrate) 
13478-10-9 (tetrahydrate) 
ChEBI CHEBI:30812 Yes
ChemSpider 22866 Yes
Jmol-3D images Image
PubChem 24458
RTECS number NO5400000
UNII S3Y25PHP1W Yes
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)
2.39 g/cm3 (dihydrate)
1.93 g/cm3 (tetrahydrate)
Melting point 677 °C (1,251 °F; 950 K) (anhydrous)
120 °C (dihydrate)
105 °C (tetrahydrate) [1]
Boiling point 1,023 °C (1,873 °F; 1,296 K) (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
Solubility in ethanol 100 g/100 mL (value should be double checked , experiment shows merely soluble(anhydrous))
Structure
Crystal structure Monoclinic
octahedral at Fe
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
0
3
0
US health exposure limits (NIOSH):
TWA 1 mg/m3[2]
Related compounds
Other anions
 Iron(II) fluoride
Iron(II) bromide
Iron(II) iodide
Other cations
 Cobalt(II) chloride
Manganese(II) chloride
Copper(II) chloride
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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.

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:

Fe + 2 HCl → FeCl2 + H2

The spent acid requires treatment before its disposal. It is also byproduct from titanium production, since some titanium ores contain iron.[3]

Laboratory preparation

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.[4] FeBr2 and FeI2 can be prepared analogously.

Fe + 2HCl + 2CH3OH → FeCl2 + CH4 + H2O

An alternative laboratory synthesis of FeCl2 entails the reaction of FeCl3 with chlorobenzene:[5]

2 FeCl3 + C6H5Cl → 2 FeCl2 + C6H4Cl2 + HCl

FeCl2 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.[6] 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.[7]

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.[3] Ferrous chloride is employed as a reducing agent in many organic synthesis reactions.

References

  1. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ↑ "NIOSH Pocket Guide to Chemical Hazards #0346". National Institute for Occupational Safety and Health (NIOSH).
  3. ↑ 3.0 3.1 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.
  4. ↑ G. Winter; Thompson, D. W.; Loehe, J. R. (1973). "Iron(II) Halides". Inorg. Synth. 14: 99–104. doi:10.1002/9780470132456.ch20.
  5. ↑ P. Kovacic and N. O. Brace (1960). "Iron(II) Chloride". Inorg. Synth. 6: 172. doi:10.1002/9780470132371.ch54.
  6. ↑ G. Wilkinson (1963). "Ferrocene". Org. Synth.; Coll. Vol. 4, p. 473
  7. ↑ 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.

See also