Iron(II) bromide

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
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 hydrates.

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.

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]-.