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. RuCl3 exists is two crystalline modifications. The black α-form adopts the CrCl3-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.
RuCl3 vapour decomposes into the elements at high temperatures ; the enthalpy change at 750 °C (1020 K), ΔdissH1020 has been estimated as +240 kJ/mol.
Read more about this topic: Ruthenium(III) Chloride
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