Iron(II) iodide is an inorganic compound with the chemical formula FeI2.[1][2] It is used as a catalyst in organic reactions.
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| IUPAC name
Iron(II) iodide
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| Other names
Ferrous iodide
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| Identifiers | |
3D model (JSmol)
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| ECHA InfoCard | 100.029.119 |
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CompTox Dashboard (EPA)
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| Properties | |
| FeI2 | |
| Molar mass | 309.65 g/mol |
| Appearance | White to off-white or grey[1] powder |
| Density | 5.315 g/cm3 |
| Melting point | 587 °C (1,089 °F; 860 K) |
| Boiling point | 827 °C (1,521 °F; 1,100 K) |
| soluble | |
| +13,600·10−6 cm3/mol | |
| Related compounds | |
Other anions
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Iron(II) fluoride Iron(II) chloride Iron(II) bromide |
Other cations
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Manganese(II) iodide Cobalt(II) iodide |
| Iron(III) iodide | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation
editIron(II) iodide can be synthesised by the reaction of iron with iodine at 500 °C:[1][3]
- Fe + I2 → FeI2
This is in contrast to the other iron(II) halides, which are best prepared by reaction of heated iron with the appropriate hydrohalic acid.
- Fe + 2 HX → FeX2 + H2
Alternatively, the synthesis can be carried out by treating freshly reduced iron with concentrated hydriodic acid under a nitrogen atmosphere in methanol. The initially obtained hexamethanol solvate is then thermally decomposed to anhydrous iodide:
- Fe + 2 HI + 6 MeOH → FeI2·6MeOH + H2
- FeI2·6 MeOH → FeI2 + 6 MeOH
Extremely finely divided iron(II) iodide is obtained by thermal decomposition of tetracarbonyldiiodidoiron(II) (Fe(CO)4I2).[3]
In contrast to the ferrous fluoride, chloride and bromide, which form known hydrates, the diiodide is speculated to form a stable tetrahydrate but it not been characterized directly.[4]
Chemical properties
editIron(II) iodide is a hygroscopic red-violet to black solid that is soluble in water, ethanol and diethyl ether. Rapid oxidation occurs in solution and in moist air.[5] It turns whitish when exposed to air. The solution in water is colorless.
Dissolving iron metal in hydroiodic acid is another route to aqueous solutions of iron(II) iodide. Crystalline hydrates precipitate from these solutions.[1][clarification needed]
Physical properties
editIron(II) iodide adopts the same crystal structure as cadmium iodide (CdI2).[1] It crystallizes in the trigonal crystal system of the cadmium hydroxide type with the space group P3m1 (space group no. 164) and lattice constants a = 404 pm, c = 675 pm.[3][6]
Applications
editIron(II) iodide is used as an ingredient in homeopathic medicines. In the field of application it is known as Ferrum jodatum. However, the attributed effect, particularly against glandular diseases, has not been scientifically confirmed.
It is also used for the production of alkali iodides.[6]
See also
edit- Iron(III) iodide, FeI3, unstable
References
edit- ^ a b c d e Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1083–1084. ISBN 978-0-08-037941-8.
- ^ University of Akron Chemical Database Archived 2012-12-12 at archive.today
- ^ a b c Handbuch der präparativen anorganischen Chemie. 3 (3., umgearb. Aufl ed.). Stuttgart: Enke. 1981. ISBN 978-3-432-87823-2.
- ^ Wren, J.C; Glowa, G.A; Merritt, J (1999). "Corrosion of stainless steel by gaseous I2". Journal of Nuclear Materials. 265 (1–2): 161–177. doi:10.1016/s0022-3115(98)00504-2. ISSN 0022-3115.
- ^ Lautenschläger, Karl-Heinz; Schröter, Werner; Wanninger, Andrea (2007). Taschenbuch der Chemie (20., überarb. u. erw. Aufl., [Ausg. mit CD-ROM] ed.). Frankfurt am Main: Deutsch. ISBN 978-3-8171-1760-4.
- ^ a b Ans, Jan d'; Ans, Jan d' (1998). Elemente, anorganische Verbindungen und Materialien. Taschenbuch für Chemiker und Physiker / D'Ans (4., neubearb. u. rev. Aufl ed.). Ort nicht ermittelbar: Verlag nicht ermittelbar. ISBN 978-3-540-60035-0.