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Iron(II) chloride

Structure of anhydrous ferrous chloride (

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hydrated ferrous chloride

structure of tetrahydrate

IUPAC names

Iron(II) chloride
Iron dichloride

Other names

Ferrous chloride


CAS Number

  • 7758-94-3 check
  • 16399-77-2 (dihydrate) ☒
  • 13478-10-9 (tetrahydrate) ☒

3D model (JSmol)

  • Interactive image
  • CHEBI:30812 check
  • 22866 check
ECHA InfoCard 100.028.949 Edit this at Wikidata
EC Number
  • 231-843-4

PubChem CID

  • 24458
RTECS number
  • NO5400000
  • S3Y25PHP1W check

CompTox Dashboard (EPA)

  • DTXSID9029695 Edit this at Wikidata


  • InChI=1S/2ClH.Fe/h2*1H;/q;;+2/p-2 check


  • InChI=1/2ClH.Fe/h2*1H;/q;;+2/p-2



  • Cl[Fe]Cl


Chemical formula

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)
Boiling point 1,023 °C (1,873 °F; 1,296 K) (anhydrous)

Solubility in water

64.4 g/100 mL (10 °C),
68.5 g/100 mL (20 °C),
105.7 g/100 mL (100 °C)
Solubility in THF Soluble
log P −0.15
+14750·10−6 cm3/mol

Crystal structure


Coordination geometry

Octahedral at Fe

ATC code

B03AA05 (WHO)
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code


NIOSH (US health exposure limits):

REL (Recommended)

TWA 1 mg/m3[1]
Safety data sheet (SDS) Iron (II) chloride MSDS
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 otherwise noted, data are 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. The compound is white, but typical samples are often off-white. FeCl2 crystallizes from water as the greenish tetrahydrate, which is the sườn that is most commonly encountered in commerce and the laboratory. There is also a dihydrate. The compound is highly soluble in water, giving pale green solutions.


Structure of "FeCl2(thf)x", Fe4Cl8(thf)6, illustrating both tetrahedral and octahedral coordination geometries.[2]

Hydrated forms of ferrous chloride are generated by treatment of wastes from steel production with hydrochloric acid. Such solutions are designated "spent acid," or "pickle liquor" especially when the hydrochloric acid is not completely consumed:

Fe + 2 HCl → FeCl2 + H2

The production of ferric chloride involves the use of ferrous chloride. Ferrous chloride is also a byproduct from the production of titanium, since some titanium ores contain iron.[3]

Anhydrous FeCl2[edit]

Ferrous chloride is prepared by addition of iron powder to lớn a solution of hydrochloric acid in methanol. This reaction gives the methanol solvate of the dichloride, which upon heating in a vacuum at about 160 °C converts to lớn anhydrous FeCl2.[4] The net reaction is shown:

Fe + 2 HCl → FeCl2 + H2

FeBr2 and FeI2 can be prepared analogously.

An alternative synthesis of anhydrous ferrous chloride is the reduction of FeCl3 with chlorobenzene:[5]

2 FeCl3 + C6H5Cl → 2 FeCl2 + C6H4Cl2 + HCl

For the preparation of ferrocene ferrous chloride is generated in situ by comproportionation of FeCl3 with iron powder in tetrahydrofuran (THF).[6] Ferric chloride decomposes to lớn ferrous chloride at high temperatures.


The dihydrate, FeCl2(H2O)2, crystallizes from concentrated hydrochloric acid.[7] The dihydrate is a coordination polymer. Each Fe center is coordinated to lớn four doubly bridging chloride ligands. The octahedron is completed by a pair of mutually trans aquo ligands.[8]

Subunit of FeCl2(H2O)2 lattice.


Tetra(pyridine)iron dichloride is prepared by treating ferrous chloride with pyridine.[9]

FeCl2 and its hydrates sườn complexes with many ligands. For example, solutions of the hydrates react with two molar equivalents of [(C2H5)4N]Cl to lớn give the salt [(C2H5)4N]2[FeCl4].[10]

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The anhydrous FeCl2, which is soluble in THF,[2] is a standard precursor in organometallic synthesis. FeCl2 is used to lớn generate NHC complexes in situ for cross coupling reactions.[11]


Unlike the related ferrous sulfate and ferric chloride, ferrous chloride has few commercial applications. 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.[12] It is used for odor control in wastewater treatment. It is used as a precursor to lớn make various grades of hematite that can be used in a variety of pigments. It is the precursor to lớn hydrated iron(III) oxides that are magnetic pigments.[3] FeCl2 finds some use as a reagent in organic synthesis.[13]

Natural occurrence[edit]

Lawrencite, (Fe,Ni)Cl2, is the natural counterpart, and a typically (though rarely occurring) meteoritic mineral.[14] The natural sườn of the dihydrate is rokühnite - a very rare mineral.[15] Related, but more complex (in particular, basic or hydrated) minerals are hibbingite, droninoite and kuliginite.


  1. ^ NIOSH Pocket Guide to lớn Chemical Hazards. "#0346". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b Cotton, F. A.; Luck, R. L.; Son, K.-A. (1991). "New polynuclear compounds of iron(II) chloride with oxygen donor ligands Part I. Fe4Cl8(THF)6: synthesis and a single crystal X-ray structure determination". Inorganica Chimica Acta. 179: 11–15. doi:10.1016/S0020-1693(00)85366-9.
  3. ^ 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.
  4. ^ G. Winter; Thompson, D. W.; Loehe, J. R. (1973). "Iron(II) Halides". Inorganic Syntheses. pp. 99–104. doi:10.1002/9780470132456.ch20. ISBN 978-0-470-13245-6.
  5. ^ P. Kovacic and N. O. Brace (1960). "Iron(II) Chloride". Inorganic Syntheses. pp. 172–173. doi:10.1002/9780470132371.ch54. ISBN 978-0-470-13237-1.
  6. ^ Wilkinson, G. (1956). "Ferrocene". Organic Syntheses. 36: 31. doi:10.15227/orgsyn.036.0031.
  7. ^ K. H.. Gayer; L. Woontner (1957). "Iron(II) Chloride 2‐Hydrate". Inorganic Syntheses. pp. 179–181. doi:10.1002/9780470132364.ch48. ISBN 978-0-470-13236-4.
  8. ^ Morosin, B.; Graeber, E. J. (1965). "Crystal structures of manganese(II) and iron(II) chloride dihydrate". Journal of Chemical Physics. 42 (3): 898–901. Bibcode:1965JChPh..42..898M. doi:10.1063/1.1696078.
  9. ^ Baudisch, Oskar; Hartung, Walter H. (1939). "Tetrapyridino-Ferrous Chloride (Yellow Salt)". Inorganic Syntheses. Vol. 1. pp. 184–185. doi:10.1002/9780470132326.ch64. ISBN 978-0-470-13232-6.
  10. ^ N. S. Gill, F. B. Taylor (1967). "Tetrahalo Complexes of Dipositive Metals in the First Transition Series". Inorganic Syntheses. pp. 136–142. doi:10.1002/9780470132401.ch37. ISBN 978-0-470-13240-1.
  11. ^ Bi-Jie Li; Xi-Sha Zhang; Zhang-Jie Shi (2014). "Cross-Coupling of Alkenyl/Aryl Carboxylates with Grignard Reagents via Fe-Catalyzed C-O Bond Activation". Org. Synth. 91: 83–92. doi:10.15227/orgsyn.091.0083.
  12. ^ Jameel, Pervez (1989). "The Use of Ferrous Chloride to lớn Control Dissolved Sulfides in Interceptor Sewers". Journal (Water Pollution Control Federation). 61 (2): 230–236. JSTOR 25046917.
  13. ^ Andrew D. White; David G. Hilmey (2009). "Iron(II) Chloride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.ri055.pub2. ISBN 978-0-471-93623-7.
  14. ^ "Lawrencite".
  15. ^ "Rokühnite".

See also[edit]

  • Iron(III) chloride
  • Iron(II) sulfate