Ruthenium(III) bromide explained

Ruthenium(III) bromide is a chemical compound of ruthenium and bromine with the formula RuBr₃. It is a dark brown solid that decomposes above 400 °C.

Preparation

Ruthenium(III) bromide can be prepared by the reaction of ruthenium metal with bromine at high temperature and pressure (720 K and 20 bar):

2 Ru + 3 Br₂ → 2 RuBr₃

Structure

The crystal structures of ruthenium(III) bromide contain parallel (RuBr₃)_∞ columns. The compound undergoes a phase transition around 384 K (111 °C) from an ordered orthorhombic structure in space group Pnmm with alternating long and short Ru-Ru distances to a disordered hexagonal TiI₃-like structure in space group P6₃/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.^[1]

Notes and References

1. S. . Merlino . L. . Labella . F. . Marchetti . S. . Toscani . Order−Disorder Transformation in RuBr₃ and MoBr₃: A Two-Dimensional Ising Model . . 2004 . 16 . 20 . 3895–3903 . 10.1021/cm049235q .