Iron(II) iodide is an
inorganic compound
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''.
Inorgan ...
with the
chemical formula
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
FeI
2.
It is used as a catalyst in organic reactions.
Preparation
Iron(II) iodide can be synthesised by the reaction of
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
with
iodine at 500 °C:
:
This is in contrast to the other iron(II) halides, which are best prepared by reaction of heated iron with the appropriate
hydrohalic acid.
:
Alternatively, the synthesis can be carried out by treating freshly reduced iron with concentrated
hydriodic acid under a
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
atmosphere in
methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
. The initially obtained hexamethanol solvate is then thermally decomposed to anhydrous iodide:
:
::
Extremely finely divided iron(II) iodide is obtained by thermal decomposition of tetracarbonyldiiodidoiron(II) (Fe(CO)
4I
2).
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.
Chemical properties
Iron(II) iodide is a hygroscopic red-violet to black solid that is soluble in
water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
,
ethanol
Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
and
diethyl ether
Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...
. Rapid oxidation occurs in solution and in moist air.
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.
Physical properties
Iron(II) iodide adopts the same
crystal structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...
as
cadmium iodide (CdI
2).
It crystallizes in the
trigonal crystal system of the
cadmium hydroxide type with the
space group ''P'm1'' (space group no. 164) and
lattice constants ''a'' = 404 pm, ''c'' = 675 pm.
Applications
Iron(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.
See also
*
Iron(III) iodide, FeI
3, unstable
References
{{Iodides
Iron(II) compounds
Iodides
Antianemic preparations