Iron(II) bromide is an
inorganic compound with the chemical formula FeBr
2. The anhydrous compound is a yellow or brownish-colored paramagnetic solid. Several
hydrates
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
of FeBr
2 are also known, all being pale colored solids. It is a common precursor to other iron compounds in research laboratory, but no applications exist for this compound.
Structure
Like most metal halides, FeBr
2 adopts a polymeric structure consisting of isolated metal centers cross-linked with halides. It crystallizes with the CdI
2 structure, featuring close-packed layers of bromide ions, between which are located Fe(II) ions in octahedral holes. The packing of the halides is slightly different from that for FeCl
2, which adopts the CdCl
2 motif. The tetrahydrates FeX
2(H
2O)
4 (X = Cl, Br) have similar structures, with octahedral metal centers and mutually trans halides.
Synthesis and reactions
FeBr
2 is synthesized using a
methanol solution of concentrated
hydrobromic acid
Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains 47.6% HBr by mass, which is 8.77 mol/L. ...
and iron powder. It adds the methanol solvate
e(MeOH)6r
2 together with hydrogen gas. Heating the methanol complex in a vacuum gives pure FeBr
2.
FeBr
2 reacts with two equivalents of
tetraethylammonium bromide to give
C2H5)4Nsub>2FeBr
4. FeBr
2 reacts with bromide and bromine to form the intensely colored, mixed-valence species
eBr3Br9sup>−.
Magnetism
FeBr
2 possesses a strong
metamagnetism at 4.2
K and has long been studied as a prototypical metamagnetic compound.
References
{{bromine compounds
Bromides
Iron(II) compounds
Metal halides