Iron(II) bromide

Iron(II) bromide is an inorganic compound with the chemical formula FeBr2. The anhydrous compound is a yellow or brownish-colored paramagnetic solid. Several hydrates 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.

Iron(II) bromide
Names
IUPAC name
Iron(II) bromide
Other names
Ferrous bromide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.029.244
UNII
Properties
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)
117 g / 100 ml
Solubility in other solvents THF, methanol, ethanol
+13,600·10−6 cm3/mol
Structure
Rhombohedral, hP3, SpaceGroup = P-3m1, No. 164
octahedral
Hazards
Main hazards none
R-phrases (outdated) R20 R36/37/38
S-phrases (outdated) S26 S36
Related compounds
Other anions
 Iron(II) chloride
Other cations
 iron(III) bromide
Related compounds
 VBr2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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.

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.[2]

FeBr2 reacts with two equivalents of tetraethylammonium bromide to give [(C2H5)4N]2FeBr4.[3] FeBr2 reacts with bromide and bromine to form the intensely colored, mixed-valence species [FeBr3Br9]−.[4]

Magnetism

FeBr2 possesses a strong metamagnetism at 4.2 K and has long been studied as a prototypical metamagnetic compound.[5][6]

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References
  1. Haberecht, J.; Borrmann, Η.; Kniep, R. (2001). "Refinement of the crystal structure of iron dibromide, FeBr2". Zeitschrift für Kristallographie - New Crystal Structures. 216 (1–4). doi:10.1524/ncrs.2001.216.14.544.
  2. Winter, G. (1973). "Iron(II) Halides". Inorganic Syntheses. 14: 99–104. doi:10.1002/9780470132456.ch20. ISBN 9780470132456.
  3. N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142. doi: 10.1002/9780470132401.ch37
  4. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5
  5. Wilkinson, M. K.; Cable, J. W.; Wollan, E. O.; Koehler, W. C. (15 January 1959). "Neutron Diffraction Investigations of the Magnetic Ordering in FeBr2, CoBr2, FeCl2, and CoCl2". Physical Review. 113 (2): 497–507. Bibcode:1959PhRv..113..497W. doi:10.1103/PhysRev.113.497.
  6. Jacobs, I. S.; Lawrence, P. E. (10 December 1967). "Metamagnetic Phase Transitions and Hysteresis in FeCl2". Physical Review. 164 (2): 866–878. Bibcode:1967PhRv..164..866J. doi:10.1103/PhysRev.164.866.
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