Iron(II) chloride
1558629
217707719
2008-06-07T08:11:20Z
LordAnubisBOT
2572294
robot Modifying: [[ru:Хлорид железа (II)]]
{{Chembox new
| Name = Iron(II) chloride
| IUPACName = Iron(II) chloride<br />
| OtherNames = Ferrous chloride,<br />Rokühnite (dihydrate)
| Section1 = {{Chembox Identifiers
| CASOther ={{CASREF|CAS=7758-94-3}} (''anhydr.'')<br />{{CASREF|CAS=13478-10-9}} (tetrahydrate)
| EINECS =
}}
| Section2 = {{Chembox Properties
| Formula = FeCl<sub>2</sub>
| MolarMass = 126.751 g/mol (anhydrous)<br />198.8102 g/mol ([[tetrahydrate]])
| Appearance = anhydrous: tan<br />tetrahydrate: pale green
| Density = 3.16 g/mL g/cm<sup>3</sup>, solid
| Solvent = [[THF]]
| SolubleOther = soluble
| Solubility = 64.4 g/100 mL (10°C),<br />105.7 g/100 mL (100°C)
| Solvent2 = [[ethanol]]
| SolubleOther2 = 100 g/100 mL
| MeltingPt = 677 °C
}}
| Section3 = {{Chembox Structure
| Coordination = octahedral at Fe
| CrystalStruct = [[Monoclinic]]
}}
| Section8 = {{Chembox Related
| OtherCpds = [[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 has a high melting point, [[paramagnetic]] solid, usually obtained as an off-white solid. FeCl<sub>2</sub> [[crystallizes]] from water as the greenish [[Water of crystallization|tetrahydrate]], which is how the salt is most commonly encountered in commerce and the laboratory.
==Synthesis==
A classical synthesis of metal halides involves the action of hydrogen chloride on the metal.
::[[iron|Fe]] + 2 HCl → FeCl<sub>2</sub> + [[hydrogen|H<sub>2</sub>]]
For FeCl<sub>2</sub>, the synthesis is more conveniently conducted using a [[methanol]] solution of concentrated [[hydrochloric acid]]. Reaction of this with iron gives the methanol solvate [Fe(MeOH)<sub>6</sub>]Cl<sub>2</sub>, which upon heating in a vacuum at ''ca.'' 160 °C gives pure FeCl<sub>2</sub>.<ref>G. Winter, Inorganic Synthesis, 1973, volume 14, pp. 101-104.</ref> FeBr<sub>2</sub> and FeI<sub>2</sub> can be prepared analogously.
An alternative laboratory synthesis of FeCl<sub>2</sub> entails the reaction of [[ferric chloride|FeCl<sub>3</sub>]] with [[chlorobenzene]]:<ref>P. Kovacic and N. O. Brace, Inorganic Synthesis, 1960, volume 6, p. 172.</ref><ref> P. Kovacic and N. O. Brace, J. Am. Chem. Soc., 1954, volume 76, p. 5491.</ref>
::2FeCl<sub>3</sub> + C<sub>6</sub>H<sub>5</sub>Cl → 2FeCl<sub>2</sub> + C<sub>6</sub>H<sub>4</sub>Cl<sub>2</sub> + [[hydrogen chloride|HCl]]
FeCl<sub>2</sub> prepared in this way exhibits convenient solubility in [[tetrahydrofuran]], a common solvent for chemical reactions.
For one of his two classic syntheses of [[ferrocene]], [[Geoffrey Wilkinson|Wilkinson]] generated FeCl<sub>2</sub> by heating FeCl<sub>3</sub> with iron powder.<ref>G. Wilkinson, "Ferrocene", Organic Syntheses, Coll. Vol. 4, p.473 (1963); Vol. 36, p.31 (1956).</ref>
==Hydrated and aqueous ferrous chloride==
FeCl<sub>2</sub> forms complexes with many ligands. Its most common derivative is the hydrate, FeCl<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>.
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. The spent acid requires treatment before its disposal.
==Reactions==
FeCl<sub>2</sub> reacts with two molar equivalents of [(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>−</nowiki></sup>, [MnBr<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup>, [MnI<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup>, [FeBr<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup>, [CoCl<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup>, [CoBr<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup>, [NiCl<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup> and [CuCl<sub>4</sub>]<sup>2<nowiki>−</nowiki></sup> salts.<ref>N. S. Gill & F. B. Taylor, Inorganic Synthesis, 1967, volume 9, pp. 136-142.</ref>
==References==
<references/>
==See also==
* [[Hydrochloric acid]]
* [[Iron(III) chloride]]
* [[Iron(II) sulfate]]
[[Category:Chlorides]]
[[Category:Inorganic compounds]]
[[Category:Iron compounds]]
[[Category:Metal halides]]
[[ar:كلوريد حديد ثنائي]]
[[de:Eisen(II)-chlorid]]
[[es:Cloruro de hierro (II)]]
[[fr:Chlorure de fer (II)]]
[[ja:塩化鉄(II)]]
[[pl:Chlorek żelaza(II)]]
[[pt:Cloreto de ferro (II)]]
[[ru:Хлорид железа (II)]]
[[zh:氯化亚铁]]