Iron(II) iodide
IUPAC name
Iron(II) iodide
Other names
Ferrous iodide
3D model (JSmol)
ECHA InfoCard 100.029.119 Edit this at Wikidata
EC Number
  • 232-031-2
  • InChI=1S/Fe.2HI/h;2*1H/q+2;;/p-2
  • InChI=1/Fe.2HI/h;2*1H/q+2;;/p-2
  • [Fe+2].[I-].[I-]
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)
+13,600·10−6 cm3/mol
Related compounds
Other anions
Iron(II) fluoride
Iron(II) chloride
Iron(II) bromide
Other cations
Manganese(II) iodide
Cobalt(II) iodide
Related Iron iodides
Iron(III) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Iron(II) iodide is an inorganic compound with the chemical formula FeI2.[1][2] It is used as a catalyst in organic reactions.


Iron(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

Iron(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

Iron(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 parameters a = 404 pm, c = 675 pm.[3][6]


Iron(II) iodide is used as an active 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 prouction of alkali iodides.[6]

See also


  1. ^ 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.
  2. ^ University of Akron Chemical Database Archived 2012-12-12 at
  3. ^ a b c Handbuch der präparativen anorganischen Chemie. 3 (3., umgearb. Aufl ed.). Stuttgart: Enke. 1981. ISBN 978-3-432-87823-2.
  4. ^ 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.
  5. ^ 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.
  6. ^ 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.