Iridium(III) chloride

Iridium(III) chloride is the chemical compound with the formula IrCl3. This salt and the related hydrate are the principal starting materials for most iridium chemistry. The anhydrous salt is a dark green crystalline solid, which is very hygroscopic. It is usually encountered as a non-stoïchiometric hydrate CAS number [14996-61-3]) which has a highly variable water content.

Preparation
Iridium is separated from the other platinum group metals as crystalline ammonium hexachloroiridate(IV), [NH4]2[IrCl6] (CAS number [16940-92-4]), which can be reduced to iridium metal in a stream of hydrogen. The spongy metal produced is reacted with chlorine at 300-400°C to produce iridium(III) chloride.

Uses
Iridium(III) chloride is used as a starting material for the preparation of other iridium compounds. Vaska's complex, trans-[IrCl(CO)(PPh3)2], is prepared by refluxing IrCl3 in dimethylformamide with excess triphenylphosphine. Alkene complexes such as the dimeric {Ir(COD)Cl}2, and {Ir(cycloctene)2Cl}2 undefined can also be prepared by refluxing IrCl3 with the appropriate alkene in water/alcohol mixtures.

Safety
Iridium(III) chloride is not listed under Annex I of Directive 67/548/EEC, but is usually classified as irritant, R36/37/38: Irritating to eyes, respiratory system and skin. It is listed in the inventory of the Toxic Substances Control Act (TSCA).