Iron(II) chloride

Structure of anhydrous ferrous chloride ( Fe,  Cl)

hydrated ferrous chloride

structure of tetrahydrate

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Names
IUPAC names

Iron(II) chloride
Iron dichloride

Other names

Ferrous chloride
Rokühnite

Identifiers

CAS Number

* 7758-94-3 Y
* 16399-77-2 (dihydrate) N
* 13478-10-9 (tetrahydrate) N

3D model (JSmol)

* Interactive image

ChEBI |

* CHEBI:30812 Y

ChemSpider |

* 22866 Y

EC Number |

* 231-843-4

PubChem CID

* 24458

RTECS number |

* NO5400000

UNII |

* S3Y25PHP1W Y

InChI

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

Key: NMCUIPGRVMDVDB-UHFFFAOYSA-L Y

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

Key: NMCUIPGRVMDVDB-NUQVWONBAL

SMILES

* Cl[Fe]Cl

Properties

Chemical formula

| 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)
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

Magnetic susceptibility (χ)

| +14750·10−6 cm3/mol
Structure

Crystal structure

| Monoclinic

Coordination geometry

| Octahedral at Fe
Pharmacology
1=ATC code }}  | B03AA05 (WHO)
Hazards
Safety data sheet | Iron (II) chloride MSDS
NFPA 704 (fire diamond)  |

NIOSH (US health exposure limits):

REL (Recommended)

| TWA 1 mg/m3[1]
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).

N verify (what is YN ?)
Infobox references

Tracking categories (test):

* SizeSet
* PairSizeSet

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 form 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.

## Contents

* 1 Production
* 2 Anhydrous FeCl2
* 3 Hydrates
* 4 Reactions
* 5 Applications
* 6 Natural occurrence
* 7 References
* 8 See also

## Production

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

Ferrous chloride is prepared by addition of iron powder to 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 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 ferrous chloride at high temperatures.

## Hydrates

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

Subunit of FeCl2(H2O)2 lattice.

## Reactions

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

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

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

## Applications

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 make various grades of hematite that can be used in a variety of pigments. It is the precursor to hydrated iron(III) oxides that are magnetic pigments.[3] FeCl2 finds some use as a reagent in organic synthesis.[13]

## Natural occurrence

Lawrencite, (Fe,Ni)Cl2, is the natural counterpart, and a typically (though rarely occurring) meteoritic mineral.[14] The natural form 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.

## References

1. ↑ NIOSH Pocket Guide to Chemical Hazards. "#0346". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0346.html.
2. ↑ 2.0 2.1 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. ↑ 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". Inorganic Syntheses. 14. 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. 6. 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. 5. 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. doi:10.1063/1.1696078. Bibcode: 1965JChPh..42..898M.
9. ↑ Baudisch, Oskar; Hartung, Walter H. (1939). "Tetrapyridino-Ferrous Chloride (Yellow Salt)". Inorganic Syntheses. 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. 9. 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 Control Dissolved Sulfides in Interceptor Sewers". Journal (Water Pollution Control Federation) 61 (2): 230–236.
13. ↑ Andrew D. White; David G. Hilmey (2009). Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.ri055.pub2. ISBN 978-0-471-93623-7.
14. ↑ "Lawrencite". https://www.mindat.org/min-2351.html.
15. ↑ "Rokühnite". https://www.mindat.org/min-3440.html.

## See also

* Iron(III) chloride
* Iron(II) sulfate

* v
* t
* e

Antianemic preparations (B03)

Erythropoietins|

* Erythropoietin
* Darbepoetin alfa
* Methoxy polyethylene glycol-epoetin beta
* Peginesatide

Iron supplements|

* Ferric hydroxide
* Ferric maltol
* Ferrous ascorbate
* Ferrous aspartate
* Ferrous carbonate
* Ferrous chloride
* Ferric derisomaltose
* Ferrous fumarate
* Ferrous gluconate
* Ferrous glycine sulfate
* Ferrous iodine
* Ferrous succinate
* Ferrous sulfate
* Ferrous tartrate
* Iron sucrose
* Sodium ferric gluconate complex

Vitamin B12 and
folic acid supplements|

* Cyanocobalamin
* Cyanocobalamin tannin complex
* Hydroxocobalamin
* Cobamamide
* Mecobalamin
* Folic acid

Other|

* Luspatercept
* Roxadustat

* v
* t
* e

Iron compounds

Fe(-II)|

* Na2Fe(CO)4

Fe(0)|

* Fe(CO)5
* Fe2(CO)9
* Fe3(CO)12
* Fe(CO)3CH3COC2H2C6H6

Fe(I)|

* FeH

| Organoiron(I) compounds|

* (C5H5FeCO)2(CO)2

|

Fe(0,II)|

* Fe3C

Fe(II)|

* FeBr2
* FeCl2
* FeF2
* FeI2
* FeH2
* FeMoO4
* FeO
* Fe(OH)2
* FeS
* FeSO4
* FeSe
* FeSeO4
* FeSi2
* FeTiO3
* FeCO3
* FeC2O4
* Fe(C2H3O2)2
* Fe(C3H5O3)2
* FeC6H6O7
* FeC12H22O14
* Fe2CrO4
* Fe3(PO4)2
* H2Fe(CO)4
* Fe(HCO3)2
* Mg2FeH6

| Organoiron(II) compounds|

* Fe(C5H5)2
* Fe(C5H4P(C6H5)2)2
* C4H4Fe(CO)3
* C4H6Fe(CO)3

|

Fe(0,III)|

* Fe3P

Fe(II,III)|

* Fe3O4
* Fe3S4

Fe(III)|

* FeBr3
* FeCl3
* FeF3
* FeI3
* Fe(NO3)3
* Fe(acac)3
* FeOCl
* FeO(OH)
* FePO4
* Fe4(P2O7)3
* Fe2(CrO4)3
* Fe2(C2O4)3
* Fe2O3
* Fe2S3
* Fe2(SO4)3
* FeBO3
* FeB

| Organoiron(III) compounds|

* Fe(C5H5)2BF4
* C6H8O7⋅xFe3+⋅yNH3

|

Fe(VI)|

* K2FeO4
* BaFeO4

* v
* t
* e

Salts and covalent derivatives of the chloride ion

HCl |  |  |  | He

|
|
|
|

LiCl | BeCl2 | BCl3
B2Cl4 | CCl4 | NCl3
ClN3 | Cl2O
ClO2
Cl2O7 | ClF
ClF3
ClF5 | Ne
NaCl | MgCl2 | AlCl
AlCl3 | SiCl4 | P2Cl4
PCl3
PCl5 | S2Cl2
SCl2
SCl4 | Cl2 | Ar
KCl | CaCl
CaCl2 | ScCl3 | TiCl2
TiCl3
TiCl4 | VCl2
VCl3
VCl4
VCl5 | CrCl2
CrCl3
CrCl4 | MnCl2 | FeCl2
FeCl3 | CoCl2
CoCl3 | NiCl2 | CuCl
CuCl2 | ZnCl2 | GaCl2
GaCl3 | GeCl2
GeCl4 | AsCl3
AsCl5 | Se2Cl2
SeCl4 | BrCl | KrCl
RbCl | SrCl2 | YCl3 | ZrCl3
ZrCl4 | NbCl4
NbCl5 | MoCl2
MoCl3
MoCl4
MoCl5
MoCl6 | TcCl4 | RuCl3 | RhCl3 | PdCl2 | AgCl | CdCl2 | InCl
InCl2
InCl3 | SnCl2
SnCl4 | SbCl3
SbCl5 | Te3Cl2
TeCl4 | ICl
ICl3 | XeCl
XeCl2
CsCl | BaCl2 |  | HfCl4 | TaCl5 | WCl2
WCl3
WCl4
WCl5
WCl6 | Re3Cl9
ReCl4
ReCl5
ReCl6 | OsCl4 | IrCl2
IrCl3
IrCl4 | PtCl2
PtCl4 | AuCl
AuCl3 | Hg2Cl2,
HgCl2 | TlCl | PbCl2,
PbCl4 | BiCl3 | PoCl2,
PoCl4 | AtCl  | RnCl2
FrCl | RaCl2 |  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
LaCl3 | CeCl3 | PrCl3 | NdCl2,
NdCl3 | PmCl3 | SmCl2,
SmCl3 | EuCl2,
EuCl3 | GdCl3 | TbCl3 | DyCl2,
DyCl3 | HoCl3 | ErCl3 | TmCl2
TmCl3 | YbCl2
YbCl3 | LuCl3
AcCl3 | ThCl4 | PaCl5 | UCl3
UCl4
UCl5
UCl6 | NpCl4 | PuCl3 | AmCl2
AmCl3 | CmCl3 | BkCl3 | CfCl3 | EsCl3 | Fm  | Md  | No  | LrCl3

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