Iron(II) bromide
Encyclopedia
Iron 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 porphyrin
s.
s.
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.
Iron(II) bromide cannot be formed by the reaction of iron
and bromine
, because that reaction would produce ferric bromide.
FeBr2 reacts with bromide and bromine to form the intensely colored, mixed-valence species [FeBr3Br9]−.
FeBr2 is a weak reducing agent, as are all ferrous
compounds.
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
s.
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. The packing of the halides is slightly different from that for FeCl2, which adopts the CdCl2 motif. FeBr2 also forms hydrateHydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
s.
Synthesis
FeBr2 is conveniently synthesized using a methanolMethanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
solution of concentrated hydrobromic acid
Hydrobromic acid
Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at 124.3 °C and contains 47.6% HBr by weight, which is 8.89 mol/L. Hydrobromic acid has a pKa of −9, making it a...
. 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.
Iron(II) bromide cannot be formed by the reaction of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
, because that reaction would produce ferric bromide.
Reactions
FeBr2 reacts with (C2H5)4NBr to give [(C2H5)4N]2FeBr4.FeBr2 reacts with bromide and bromine to form the intensely colored, mixed-valence species [FeBr3Br9]−.
FeBr2 is a weak reducing agent, as are all ferrous
Ferrous
Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound ....
compounds.