Ruthenium(III) bromide is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
of
ruthenium
Ruthenium is a chemical element; it has symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is unreactive to most chem ...
and
bromine
Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...
with the formula RuBr
3. 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 Br
2 → 2 RuBr
3
Structure
The
crystal structure
In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...
s of ruthenium(III) bromide contain parallel (RuBr
3)
∞ columns. The compound undergoes a
phase transition
In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic Sta ...
around 384 K (111 °C) from an ordered orthorhombic structure in
space group
In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...
''Pnmm'' with alternating long and short Ru-Ru distances to a
disordered hexagonal
TiI3-like structure in space group ''P6
3/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.
References
{{DEFAULTSORT:Ruthenium(Iii) Bromide
Ruthenium(III) compounds
Bromides
Platinum group halides