Iron (II) bromide

Crystal structure
__ Fe 2+      __ Br -
General
Surname	Iron (II) bromide
other names	Iron dibromide Iron bromide (ambiguous) Ferrum bromatum (ambiguous)
Ratio formula	FeBr 2
Brief description	yellow to brown crystalline solid
External identifiers / databases
CAS number 7789-46-0 EC number 232-168-8 ECHA InfoCard 100.029.244 PubChem 425646 Wikidata Q421396
properties
Molar mass	215.65 g mol −1
Physical state	firmly
density	4.64 g cm −3
Melting point	688 ° C (beginning of decomposition)
boiling point	971 ° C
solubility	soluble in water
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-332-335 P: 261-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Iron (II) bromide is a chemical compound of iron and is one of the bromides .

Extraction and presentation

Iron (II) bromide can be obtained by decomposing iron (III) bromide at temperatures> 200 ° C (it therefore also occurs as an intermediate and by-product in the synthesis of FeBr ₃ from the elements ).

${\displaystyle \mathrm {2\ FeBr_{3}\longrightarrow 2\ FeBr_{2}+Br_{2}} }$

Furthermore, iron (II) bromide can be prepared from iron and ammonium bromide ( Carl Löwig 1829).

${\displaystyle \mathrm {2\ NH_{4}Br+Fe\longrightarrow FeBr_{2}+NH_{3}+H_{2}} }$

It can also be represented by reacting iron with hydrogen bromide . When using hydrobromic acid , the hexahydrate is formed when the resulting solution is dried in a vacuum below 49 ° C. The tetrahydrate is formed above this temperature, and the dihydrate above 83 ° C.

${\displaystyle \mathrm {Fe+2\ HBr\longrightarrow FeBr_{2}+H_{2}} }$

${\displaystyle \mathrm {Fe+2\ HBr+6\ H_{2}O\longrightarrow FeBr_{2}\cdot 6H_{2}O+H_{2}} }$

However, if the synthesis is carried out under a nitrogen atmosphere in methanol , the hexamethanol solvate can be prepared and isolated with concentrated aqueous hydrobromic acid , which is then thermally decomposed to anhydrous bromide:

${\displaystyle {\ce {Fe + 2 HBr ->[MeOH][] FeBr2 * 6 MeOH + H2}}}$

${\displaystyle {\ce {FeBr2 * 6 MeOH ->[T][] FeBr2 + 6 MeOH}}}$

properties

Iron (II) bromide is a light yellow to dark brown, crystalline, hygroscopic solid. It has a cadmium iodide type crystal structure with the space group P 3 m 1 (space group no. 164) with the lattice constants a = 377.6 pm and c = 622.7 pm. The hexahydrate is in the form of pale green, rhombic, non-deliquescent tablets.

Individual evidence

1. ↑ ^{a b} Iron dibromides at WebElements .
2. ↑ ^{a b} M. Armbruster, Th. Ludwig, HW Rotter, G. Thiele, H. Oppermann: About iron tribromide: Investigations of equilibria with FeBr ₃ , crystal structure and characterization . In: Journal for inorganic and general chemistry, Volume 626, Issue 1, pages 187-195, January, 2000 doi : 10.1002 / (SICI) 1521-3749 (200001) 626: 1 <187 :: AID-ZAAC187> 3.0.CO ; 2-X .
3. ↑ data sheet at Americanelements .
4. ↑ ^{a b} Datasheet Iron (II) bromide from Sigma-Aldrich , accessed on March 29, 2011 ( PDF ).
5. ↑ ^{a b c} Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1634.
6. ↑ G. Winter: Iron (II) halides . In: Aaron Wold and John K. Ruff (Eds.): Inorganic Syntheses . tape 14 . McGraw-Hill Book Company, Inc., 1973, ISBN   07-071320-0  ( defective ) , p. 101-104 (English).
7. ↑ Single crystal structure determination of iron (II) bromide, in: Jörg Haberecht: Investigation of the topotactic reaction of calcium disilicide with ammonium bromide. , Dissertation, University of Dresden 2001, p. 165 f. urn : nbn: de: swb: 14-1010568445843-90223
8. ↑ J. Haberecht, H. Borrmann, R. Kniep: Refinement of the crystal structure of iron dibromide, FeBr ₂ . In: Zeitschrift für Kristallographie - New Crystal Structures , 2001 , 216 , p. 510.