is the chemical compound
with the formula RuCl<sub>3</sub>. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl<sub>3</sub>·x
H<sub>2</sub>O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a varying proportion of water of crystallization
, often approximating to a trihydrate, is a commonly used starting material in ruthenium
Preparation and properties
The anhydrous forms of ruthenium(III) chloride are well characterized but rarely used. Crystalline material is usually prepared by heating powdered ruthenium metal to 700 °C under a 4:1 mixture of chlorine
and carbon monoxide
: the product is carried by the gas stream and crystallises upon cooling. exists is two crystalline modifications. The black α-form adopts the CrCl<sub>3</sub>-type
structure with long Ru-Ru contacts of 346 pm
. The dark brown metastable
β-form crystallizes in a hexagonal cell; this form consists of infinite chains of face-sharing octahedra with Ru-Ru contacts of 283 pm. The β-form is irreversibly converted to the α-form at 450–600 °C.
RuCl<sub>3</sub> vapour decomposes into the elements
at high temperatures ; the enthalpy change
at 750 °C (1020 K), Δ<sub>diss</sub>H
<sub>1020</sub> has been estimated as +240 kJ/mol.
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