Rokühnite

Iron(II) chloride

structure of anhydrous ferrous chloride (purple = Fe, green = Cl)
structure of tetrahydrate
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
ECHA InfoCard	100.028.949
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/100mL (20 °C), 105.7 g/100 mL (100 °C)
Solubility in THF	soluble
log P	-0.15
Magnetic susceptibility (χ)	+14,750·10−6 cm3/mol
Structure
Crystal structure	Monoclinic
Coordination geometry	octahedral at Fe
Pharmacology
ATC code	B03AA05 (WHO)
Hazards
NFPA 704	0 3 0
US health exposure limits (NIOSH):
REL (Recommended)	TWA 1 mg/m3
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  (what is YN ?)
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. FeCl₂crystallizes 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 highly transparent and pale green in color.

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. It is also byproduct from titanium production, since some titanium ores contain iron.

The dihydrate crystallizes from concentrated hydrochloric acid.

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. FeBr₂ and FeI₂ can be prepared analogously.

An alternative synthesis of entails the reduction of FeCl₃ with chlorobenzene:

FeCl₂ is soluble in tetrahydrofuran (THF). In one of two classic syntheses of ferrocene, Wilkinson generated FeCl₂ by heating FeCl₃ with iron powder in THF. Ferric chloride decomposes to ferrous chloride at high temperatures.

The dihydrate, FeCl₂(H₂O)₂, 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.