Iron(II) bromide

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Iron(II) bromide
Iron(II) bromide
Identifiers
CAS number 7789-46-0 YesY
PubChem 659170
ChemSpider 74218 YesY
Jmol-3D images Image 1
Properties
Molecular 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)
Boiling point 934 °C (1,713 °F; 1,207 K)
Solubility in water soluble
Solubility in other solvents THF, methanol, ethanol
Structure
Crystal structure Rhombohedral, hP3, SpaceGroup = P-3m1, No. 164
Coordination
geometry
octahedral
Hazards
R-phrases R20 R36/37/38
S-phrases S26 S36
Main hazards none
Related compounds
Other anions Iron(II) chloride
Other cations iron(III) bromide
Related compounds VBr2
Except where noted otherwise, 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 the chemical compound FeBr2. This brownish-colored solid is a useful synthetic intermediate; for example it is employed to insert Fe(II) into porphyrins.

Structure[edit]

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. FeBr2 also forms hydrates.

Synthesis[edit]

FeBr2 is conveniently synthesized using a methanol solution of concentrated hydrobromic acid. Addition with Fe gives the methanol solvate [Fe(MeOH)6]Br2 together with hydrogen gas. Heating the methanol complex in a vacuum at ca. 160 °C gives pure FeBr2.[2]

Iron(II) bromide cannot be formed by the reaction of iron and bromine, because that reaction would produce ferric bromide.

Reactions[edit]

FeBr2 reacts with 2 equivalents of (C2H5)4NBr to give [(C2H5)4N]2FeBr4.[3]

FeBr2 reacts with bromide and bromine to form the intensely colored, mixed-valence species [FeBr3Br9].[4]

FeBr2 is a weak reducing agent, as are all ferrous compounds.

References[edit]

  1. ^ Haberecht, J.; Borrmann, H.; Kniep, R. "Refinement of the Crystal Structure of Iron Dibromide, FeBr2 Zeitschrift für Kristallographie - New Crystal Structures (2001), volume 216, page 510.
  2. ^ G. Winter, "Iron(II) Halides" in "Inorganic Syntheses" 1973, volume 14, pages 101-104.
  3. ^ N. S. Gill, F.. B. Taylor Inorganic Syntheses 1967, volume 9, page 136-142.
  4. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5