Iron(II) bromide

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 ;
ECHA InfoCard	100.029.244
PubChem CID	425646;
UNII	EA3X054RBZ ;
CompTox Dashboard (EPA)	DTXSID201014482 DTXSID80976870, DTXSID201014482 ;
	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 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). verify (what is ?) Infobox references

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.

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]

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.
^ Waizumi, Kenji; Masuda, Hideki; Ohtaki, Hitoshi (1992). "X-ray Structural Studies of FeBr₂·4H₂O, CoBr₂·4H₂O, NiCl₂·4H₂O and CuBr₂·4H₂O. Cis/Trans Selectivity in Transition Metal(II) Dihalide Tetrahydrate". Inorganica Chimica Acta. 192 (2): 173–181. doi:10.1016/S0020-1693(00)80756-2.
^ Winter, G. (1973). "Iron(II) Halides". Inorganic Syntheses. Vol. 14. pp. 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.

[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] Waizumi, Kenji; Masuda, Hideki; Ohtaki, Hitoshi (1992). "X-ray Structural Studies of FeBr₂·4H₂O, CoBr₂·4H₂O, NiCl₂·4H₂O and CuBr₂·4H₂O. Cis/Trans Selectivity in Transition Metal(II) Dihalide Tetrahydrate". Inorganica Chimica Acta. 192 (2): 173–181. doi:10.1016/S0020-1693(00)80756-2.

[3] Winter, G. (1973). "Iron(II) Halides". Inorganic Syntheses. Vol. 14. pp. 99–104. doi:10.1002/9780470132456.ch20. ISBN 9780470132456.

[4] N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142. doi:10.1002/9780470132401.ch37

[5] Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5

[6] 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.

[7] 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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