Iron(II) chloride

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Iron(II) chloride
Anhydrous
Tetrahydrate
Structure of anhydrous ferrous chloride (  Fe,   Cl)
structure of tetrahydrate
Names
IUPAC names
Iron(II) chloride
Iron dichloride
Other names
Ferrous chloride
Rokühnite
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.028.949 Edit this at Wikidata
EC Number
  • 231-843-4
RTECS number
  • NO5400000
UNII
  • InChI=1S/2ClH.Fe/h2*1H;/q;;+2/p-2 checkY
    Key: NMCUIPGRVMDVDB-UHFFFAOYSA-L checkY
  • InChI=1/2ClH.Fe/h2*1H;/q;;+2/p-2
    Key: NMCUIPGRVMDVDB-NUQVWONBAL
  • Cl[Fe]Cl
Properties
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)
64.4 g/100 mL (10 °C),
68.5 g/100 mL (20 °C),
105.7 g/100 mL (100 °C)
THF
 Soluble
log P −0.15
+14750·10−6 cm3/mol
Structure
Monoclinic
Octahedral at Fe
Pharmacology
B03AA05 (WHO)
Hazards
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
3
0
0
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).
☒N verify (what is checkY☒N ?)

Iron(II) chloride, also known as ferrous chloride, is the

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.

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.

aquo ligands.[8]

Subunit of FeCl2(H2O)2 lattice.

Reactions

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,

cross coupling reactions.[11]

Applications

Unlike the related

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).
  2. ^
    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. ISBN 978-0-470-13245-6. {{cite book}}: |journal= ignored (help
    )
  5. ISBN 978-0-470-13237-1. {{cite book}}: |journal= ignored (help
    )
  6. doi:10.15227/orgsyn.036.0031
    .
  7. ISBN 978-0-470-13236-4. {{cite book}}: |journal= ignored (help
    )
  8. doi:10.1063/1.1696078
    .
  9. ISBN 978-0-470-13232-6
    .
  10. ISBN 978-0-470-13240-1. {{cite book}}: |journal= ignored (help
    )
  11. doi:10.15227/orgsyn.091.0083
    .
  12. JSTOR 25046917
    .
  13. ISBN 978-0-471-93623-7
    .
  14. ^ "Lawrencite".
  15. ^ "Rokühnite".

See also

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