Iron(II) bromide is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the chemical formula FeBr₂. The anhydrous compound is a yellow or brownish-colored paramagnetic solid. Several

hydrates In chemistry, a hydrate is a substance that contains water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

of FeBr₂ 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, FeBr₂ adopts a polymeric structure consisting of isolated metal centers cross-linked with halides. It crystallizes with the CdI₂ 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 FeCl₂, which adopts the CdCl₂ motif. The tetrahydrates FeX₂(H₂O)₄ (X = Cl, Br) have similar structures, with octahedral metal centers and mutually trans halides.

Synthesis and reactions

FeBr₂ is synthesized using a

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

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. H ...

and iron powder. It adds the methanol solvate e(MeOH)₆r₂ together with hydrogen gas. Heating the methanol complex in a vacuum gives pure FeBr₂. FeBr₂ reacts with two equivalents of

tetraethylammonium bromide Tetraethylammonium bromide (TEAB) is a quaternary ammonium compound with the chemical formula C8H20N+Br−, often written as "Et4N+Br−" in the chemical literature. It has been used as the source of tetraethylammonium ions in pharmacological and ...

to give C₂H₅)₄Nsub>2FeBr₄. FeBr₂ reacts with bromide and bromine to form the intensely colored, mixed-valence species eBr₃Br₉sup>−.

Magnetism

FeBr₂ possesses a strong

metamagnetism Metamagnetism is a sudden (often, dramatic) increase in the magnetization of a material with a small change in an externally applied magnetic field. The metamagnetic behavior may have quite different physical causes for different types of metamagne ...

at 4.2 K and has long been studied as a prototypical metamagnetic compound.

References

{{bromine compounds Bromides Iron(II) compounds Metal halides