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 | 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 ΔfH°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, εr, 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) Infobox 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 |
[edit] Synthesis
A classical synthesis of metal halides involves the action of hydrogen chloride on the metal.
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.[1] FeBr2 and FeI2 can be prepared analogously.
An alternative laboratory synthesis of FeCl2 entails the reaction of FeCl3 with chlorobenzene:[2] [3]
-
- 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.[4]
[edit] 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.
[edit] 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.[5]
[edit] References
- ^ G. Winter, "Iron(II) Halides" in "Inorganic Syntheses" 1973, volume 14, pages 101-104.
- ^ P. Kovacic; N. O. Brace, "Inorganic Syntheses" 1960, volume 6, pages 172.
- ^ P. Kovacic and N. O. Brace "J. Am. Chem. Soc" 1954, volume 76, page 5491.
- ^ G. Wilkinson, "Ferrocene" Organic Syntheses, Coll. Vol. 4, p.473 (1963); Vol. 36, p.31 (1956).
- ^ N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142.
