Iron(III) bromide is prepared by the action of bromine with iron filings:
2Fe + 3Br2 → 2FeBr3
The compound should be stored in dark bottles protected from air or light. It also may be obtained by double decompostion reactions between a ferric salt and a bromide (alkali metal bromide) in aqueous solution followed by evaporation and crystallization:
Fe2(SO4)3 + LiBr → 2FeBr3 + 3Li2SO4
It also may be prepared in high yield by photochemical reaction of dibromoirontetracarbonyl with bromine in hexane (Yoon, K.B. and J.K. Kochi.
1990. Inorg. Chem. 29, pp. 869):
(CO)4FeBr2 + ½ Br2 → FeBr3 + 4CO
Brown-red crystalline powder
Dark red hexagonal crystal; hygroscopic; partially decomposes to FeBr2,losing some bromine on exposure to air or light; density 4.50 g/cm3; decomposes on heating; soluble in water, ethanol, and ether.
Iron(III) bromide is used as a Lewis acid catalyst in the halogenation of aromatic compounds. It is also used in the preparation of 2,5-dibromo-4-aryl-1,3-pentadiene by reacting with homoallenic bromohydrin.
Catalyst for organic reactions, particularly in bromination of aromatic Compounds.
This product has been enhanced for catalytic efficiency.
Sublime it in a sealed tube with Br2 at 120o-200o. [Lux in Handbook of Preparative Inorganic Chemistry (Ed.Brauer) Academic Press Vol II p 1494 1965.]
