Ruthenium(III) bromide is a chemical compound of ruthenium and bromine with the formula RuBr<sub>3</sub>. It is a dark brown solid that decomposes above 400 ðC.
The crystal structures of ruthenium(III) bromide contain parallel (RuBr<sub>3</sub>)<sub>âÂÂ</sub> columns. The compound undergoes a phase transition around 384 K (111 ðC) from an ordered orthorhombic structure in space group Pnmm with alternating long and short Ru-Ru distances to a disordered hexagonal TiI<sub>3</sub>-like structure in space group P6<sub>3</sub>/mcm with (on average) equal Ru-Ru distances. In the disordered polymorph, the Ru-Ru distances are not believed to actually be equal but appear so due to a random distribution of two distinct column conformations. Both polymorphs consist of hexagonally close-packed bromide ions.
Ruthenium(III) bromide can be prepared by the reaction of ruthenium metal with bromine at high temperature and pressure (720 K and 20 bar):