Iron(II) bromide

Iron(II) bromide
Names
	IUPAC name Iron(II) bromide
	Other names Ferrous bromide
Identifiers
CAS Number	7789-46-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	74218 ;
ECHA InfoCard	100.029.244
PubChem CID	425646;
UNII	EA3X054RBZ ;
CompTox Dashboard (EPA)	DTXSID80976870 ;
	InChI InChI=1S/2BrH.Fe/h21H;/q;;+2/p-2 Key: GYCHYNMREWYSKH-UHFFFAOYSA-L ; InChI=1/2BrH.Fe/h21H;/q;;+2/p-2 Key: GYCHYNMREWYSKH-NUQVWONBAN;
	SMILES [Fe+2].[Br-].[Br-];
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
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R-phrases (outdated)	R20 R36/37/38
S-phrases (outdated)	S26 S36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

Iron(II) bromide is a 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.

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]

References

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.
Winter, G. (1973). "Iron(II) Halides". Inorganic Syntheses. 14: 99–104. doi:10.1002/9780470132456.ch20. ISBN 9780470132456.
N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142. doi: 10.1002/9780470132401.ch37
Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5
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.
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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[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.