Iron(II) bromide

Iron(II) bromide refers to inorganic compounds with the chemical formula FeBr₂(H₂O)_x. The anhydrous compound (x = 0) is a yellow or brownish-colored paramagnetic solid. The tetrahydrate is also known, all being pale colored solids. They are common precursor to other iron compounds.

Iron(II) bromide

Names
IUPAC name Iron(II) bromide
Other names Ferrous bromide
Identifiers
CAS Number	20049-61-0 tetrahydrate 7789-46-0 anhydrous
3D model (JSmol)	anhydrous: Interactive image tetrahydrate: Interactive image
ChemSpider	74218 Y
ECHA InfoCard	100.029.244
PubChem CID	425646
UNII	EA3X054RBZ Y
CompTox Dashboard (EPA)	DTXSID201014482 DTXSID80976870, DTXSID201014482
InChI InChI=1S/2BrH.Fe/h2*1H;/q;;+2/p-2 Y Key: GYCHYNMREWYSKH-UHFFFAOYSA-L Y InChI=1/2BrH.Fe/h2*1H;/q;;+2/p-2 Key: GYCHYNMREWYSKH-NUQVWONBAN
SMILES anhydrous: [Fe+2].[Br-].[Br-] tetrahydrate: Br[Fe-4](Br)([OH2+])([OH2+])([OH2+])[OH2+]
Properties
Chemical formula	FeBr2
Molar mass	215.65 g mol−1
Appearance	yellow-brown solid
Density	4.63 g cm−3, solid
Melting point	684 °C (1,263 °F; 957 K) (anhydrous) 27 °C (Hexahydrate)
Boiling point	934 °C (1,713 °F; 1,207 K)
Solubility in water	117 g / 100 ml
Solubility in other solvents	THF, methanol, ethanol
Magnetic susceptibility (χ)	+13,600·10−6 cm3/mol
Structure
Crystal structure	Rhombohedral, hP3, SpaceGroup = P-3m1, No. 164
Coordination geometry	octahedral
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	none
Related compounds
Other anions	Iron(II) fluoride Iron(II) chloride Iron(II) iodide
Other cations	Manganese(II) bromide Cobalt(II) bromide
Related compounds	Vanadium(II) bromide Iron(III) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Iron(II) bromide anhydrous

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.^[1] 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.^[2]

Synthesis and reactions

FeBr₂ is synthesized using a methanol solution of concentrated hydrobromic acid and iron powder. It adds the methanol solvate [Fe(MeOH)₆]Br₂ together with hydrogen gas. Heating the methanol complex in a vacuum gives pure FeBr₂.^[3]

FeBr₂ reacts with two equivalents of tetraethylammonium bromide to give [(C₂H₅)₄N]₂FeBr₄.^[4] FeBr₂ reacts with bromide and bromine to form the intensely colored, mixed-valence species [FeBr₃Br₉]⁻.^[5]

Magnetism

FeBr₂ possesses a strong metamagnetism at 4.2 K and has long been studied as a prototypical metamagnetic compound.^[6][7]