View source for Ferrous chloride

{{chembox
| Watchedfields = changed
| verifiedrevid = 443880274
| Name = Iron(II) chloride
| ImageFile = Iron(II)-chlorid01.png
| ImageFile2 = FeCl2.png
| ImageSize2 = 20px
| IUPACName = Iron(II) chloride<br/>Iron dichloride
| OtherNames = Ferrous chloride,<br/>[[Rokühnite]]
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 22866
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = S3Y25PHP1W
| InChI = 1/2ClH.Fe/h2*1H;/q;;+2/p-2
| InChIKey = NMCUIPGRVMDVDB-NUQVWONBAL
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 30812
| SMILES = Cl[Fe]Cl
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2ClH.Fe/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = NMCUIPGRVMDVDB-UHFFFAOYSA-L
| CASNo = 7758-94-3
| CASNo_Ref = {{cascite|correct|CAS}}
| CASOther = <br> {{CAS|16399-77-2}} (dihydrate) <br/>{{CAS|13478-10-9}} (tetrahydrate)
| PubChem = 24458
| RTECS = NO5400000
| EINECS =
| ATCCode_prefix = B03
| ATCCode_suffix = AA05
  }}
|Section2={{Chembox Properties
| Formula = FeCl<sub>2</sub>
| MolarMass = 126.751 g/mol (anhydrous)<br/>198.8102 g/mol (tetrahydrate)
| Appearance = tan solid (anhydrous)<br/>pale green solid (di-tetrahydrate)
| Density = 3.16 g/cm<sup>3</sup> (anhydrous) <br> 2.39 g/cm<sup>3</sup> (dihydrate) <br>  1.93 g/cm<sup>3</sup> (tetrahydrate)
| Solvent1 = THF
| Solubility1 = soluble
| Solubility = 64.4 g/100 mL (10&nbsp;°C),<br/>68.5 g/100mL (20&nbsp;°C),<br/>105.7 g/100 mL (100&nbsp;°C)
| Solvent2 = ethanol
| Solubility2 = 100 g/100 mL  (value should be double checked , experiment shows merely soluble(anhydrous))
| MeltingPtC = 677
| Melting_notes = (anhydrous) <br> 120&nbsp;°C (dihydrate) <br> 105&nbsp;°C (tetrahydrate) <ref>Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002, ISBN 0-07-049439-8</ref>
| BoilingPtC = 1023
| Boiling_notes = (anhydrous)
  }}
|Section3={{Chembox Structure
| Coordination = octahedral at Fe
| CrystalStruct = [[Monoclinic]]
  }}
|Section7={{Chembox Hazards
| ExternalMSDS = 
| EUClass = 
| EUIndex = 
| MainHazards = 
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 0
| NFPA-O = 
| RPhrases = 
| SPhrases = 
| FlashPt = 
| PEL = 
}}
|Section8={{Chembox Related
| OtherAnions = [[Iron(II) fluoride]]<br/>[[Iron(II) bromide]]<br/>[[Iron(II) iodide]]
| OtherCations = [[Cobalt(II) chloride]]<br/>[[Manganese(II) chloride]]<br/>[[Copper(II) chloride]]
  }}
}}

'''Iron(II) chloride''', also known as '''ferrous chloride''', is the [[chemical compound]] of formula FeCl<sub>2</sub>.  It is a [[paramagnetic]] solid with a high melting point, and is usually obtained as an off-white solid.  FeCl<sub>2</sub> [[crystallizes]] from water as the greenish [[Water of crystallization|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 FeCl<sub>2</sub> 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:
:[[iron|Fe]]  +  2 HCl  →   FeCl<sub>2</sub>  +  [[hydrogen|H<sub>2</sub>]]
The spent acid requires treatment before its disposal. It is also byproduct from titanium production, since some [[titanium]] [[ore]]s contain iron.<ref name=Ullmann>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.</ref>

==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&nbsp;°C gives [[anhydrous]] FeCl<sub>2</sub>.<ref>{{cite journal | author = G. Winter | title = Iron(II) Halides | journal = [[Inorg. Synth.]] | year = 1973 | volume = 14 | pages = 99–104 | doi = 10.1002/9780470132456.ch20 | last2 = Thompson | first2 = D. W. | last3 = Loehe | first3 = J. R.}}</ref>  FeBr<sub>2</sub> and FeI<sub>2</sub> can be prepared analogously.
: Fe + 2HCl + 2CH3OH → FeCl<sub>2</sub> + CH<sub>4</sub> + H<sub>2</sub>O

An alternative laboratory synthesis of FeCl<sub>2</sub> entails the reaction of [[ferric chloride|FeCl<sub>3</sub>]] with [[chlorobenzene]]:<ref>{{cite journal | author = P. Kovacic and N. O. Brace | journal = [[Inorg. Synth.]] | year = 1960 | volume = 6 | pages = 172 | doi = 10.1002/9780470132371.ch54 | title = Iron(II) Chloride}}</ref>
:2 FeCl<sub>3</sub>  +  C<sub>6</sub>H<sub>5</sub>Cl   →   2 FeCl<sub>2</sub>  +  C<sub>6</sub>H<sub>4</sub>Cl<sub>2</sub>  +  [[hydrogen chloride|HCl]]
FeCl<sub>2</sub> exhibits convenient solubility in [[tetrahydrofuran]] (THF), a common solvent for chemical reactions.  In one of two classic syntheses of [[ferrocene]], [[Geoffrey Wilkinson|Wilkinson]] generated FeCl<sub>2</sub> by heating FeCl<sub>3</sub> with iron powder in THF.<ref>{{OrgSynth | author = G. Wilkinson | title = Ferrocene | collvol = 4 | collvolpages = 473 | year = 1963 | prep = cv4p0473}}</ref>  Ferric chloride decomposes to ferrous chloride at high temperatures.

==Reactions==
FeCl<sub>2</sub> forms complexes with many ligands. It reacts with two molar equivalents of [[Tetraethylammonium chloride|[(C<sub>2</sub>H<sub>5</sub>)<sub>4</sub>N]Cl]] to give the salt [(C<sub>2</sub>H<sub>5</sub>)<sub>4</sub>N]<sub>2</sub>[FeCl<sub>4</sub>].  Related compounds that can be prepared similarly include the [MnCl<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, [MnBr<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, [MnI<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, [FeBr<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, [CoCl<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, [CoBr<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, [NiCl<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup>, and [CuCl<sub>4</sub>]<sup>2<nowiki>&minus;</nowiki></sup> salts.<ref>{{cite journal | author = N. S. Gill, F. B. Taylor | journal = [[Inorg. Synth.]] | year = 1967 | volume = 9 | pages = 136–142 | doi = 10.1002/9780470132401.ch37 | title = Tetrahalo Complexes of Dipositive Metals in the First Transition Series}}</ref>

==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 [[flocculation|flocculating agent]] in wastewater treatment, especially for wastes containing [[chromate]].  It is the precursor to hydrated iron(III) oxides that are magnetic pigments.<ref name=Ullmann/>  Ferrous chloride is employed as a reducing agent in many [[organic synthesis]] reactions.

==References==
<references/>

==See also==
* [[Iron(III) chloride]]
* [[Iron(II) sulfate]]

{{Iron compounds}}

[[Category:Chlorides]]
[[Category:Iron compounds]]
[[Category:Metal halides]]