Iron(II) bromide

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Iron(II) bromide
Image:Iron(II) bromide.jpg
IUPAC name	Iron(II) bromide
Other names	Ferrous bromide
Identifiers
CAS number	[7789-46-0]
Properties
Molecular formula	FeBr2
Molar mass	215.65 g/mol
Appearance	yellow-brown solid
Density	4.63 g/cm3, solid
Melting point	684 °C
Boiling point	934 °C
Solubility in water	soluble
Solubility in other solvents	THF, methanol, ethanol
Structure
Crystal structure	CdI2
Coordination geometry	octahedral in solid state
Hazards
Main hazards	none
R-phrases	20-36/37/38
S-phrases	26-36
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, 100 kPa) Infobox disclaimer and 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.

Contents 1 Structure 2 Synthesis 3 Reactions 4 References

[edit] 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. FeBr₂ also forms hydrates.

[edit] Synthesis

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]

[edit] Reactions

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

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

[edit] References

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