Iron(II) chloride

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Iron(II) chloride

General
Systematic name Iron(II) chloride

Other names ferrous chloride
Molecular formula FeCl₂
Molar mass 126.75 g/mol
Appearance buff crystals (anhydrous)
greenish crystals (tetrahydrate)
CAS number CAS=-->7758-94-3 (anhydr.)
13478-10-9 (tetrahydrate)
EINECS number ???
Properties
Density and phase 3.16 g/mL g/cm³, solid
Solubility in THF soluble
Solubility in water 64.4 g/100 mL (10°C),
105.7 g/100 mL (100°C)
Solubility in ethanol 100 g/100 mL
Melting point 677 °C
Structure
Coordination
geometry octahedral at Fe
Crystal structure Monoclinic
Thermodynamic data
Standard enthalpy
of formation Δ_fH°_solid -??? kJ/mol
for the hexahydrate?
Standard molar entropy
S°_solid ?? J.K⁻¹.mol⁻¹
for the hexahydrate?
Safety data
EU classification not listed >
PEL-TWA (OSHA) ?? mg/m³ (as Fe)
IDLH (NIOSH) ?? mg/m³ (as Fe)
Flash point non flammable
RTECS number NO5400000
Supplementary data page
Structure and
properties n, ε_r, etc.
Thermodynamic
data Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Related compounds Cobalt(II) chloride
Manganese(II) chloride
Copper(II) chloride
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
[Chemical infoboxInfobox disclaimer and references]

Iron(II) chloride, or ferrous chloride, is the chemical compound FeCl₂. It is a high melting, paramagnetic solid, usually obtained with off-white color. FeCl₂ crystallizes from water as the tetrahydrate, which the salt is most commonly encountered in commerce and the laboratory.

Contents

1 Synthesis
2 Hydrated and aqueous ferrous chloride
3 Reactions
4 References
5 See also
6 External links

Synthesis

A classical synthesis of metal halides involves the action of hydrogen chloride on the metal.

:Fe + 2 HCl → FeCl₂ + H₂

For FeCl₂, the synthesis is more conveniently conducted using a methanol solution of concentrated hydrochloric acid. Treatment with Fe gives the methanol solvate [Fe(MeOH)₆]Cl₂, which upon heating in a vacuum at ca. 160 °C gives pure FeCl₂.G. Winter, "Iron(II) Halides" in "Inorganic Syntheses" 1973, volume 14, pages 101-104. FeBr₂ and FeI₂ can be prepared analogously.

An alternative laboratory synthesis of FeCl₂ entails the reaction of FeCl₃ with chlorobenzene:P. Kovacic; N. O. Brace, "Inorganic Syntheses" 1960, volume 6, pages 172.

:2FeCl₃ + C₆H₅Cl → 2FeCl₂ + C₆H₄Cl₂ + HCl

FeCl₂ prepared in this way exhibits convenient solubility in tetrahydrofuran, a common solvent for chemical syntheses.

For one of his two classic syntheses of ferrocene, Wilkinson generated FeCl₂ by heating FeCl₃ with iron powder.G. Wilkinson, "Ferrocene" Organic Syntheses, Coll. Vol. 4, p.473 (1963); Vol. 36, p.31 (1956).

Hydrated and aqueous ferrous chloride

FeCl₂ forms complexes with many ligands. Its most fundamental derivative is the hydrate, FeCl₂(H₂O)₄.

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

FeCl₂ reacts with (C₂H₅)₄NCl to give the [(C₂H₅)₄N]₂FeCl₄. Related compounds that can be prepared similarly include [(C₂H₅)₄N]₂MnCl₄, [(C₂H₅)₄N]₂MnBr₄, [(C₂H₅)₄N]₂MnI₄, [(C₂H₅)₄N]₂FeBr₄, [(C₂H₅)₄N]₂CoCl₄, [(C₂H₅)₄N]₂CoBr₄, [(C₂H₅)₄N]₂NiCl₄, and [(C₂H₅)₄N]₂CuCl₄.N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142.

References

External links

For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].

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