Iridium(III) chloride

Iridium(III) chloride
Names
	Other names Iridium trichloride
Identifiers
CAS Number	(anhydrous), 14996-61-3 (hydrate) 10025-83-9 (anhydrous), 14996-61-3] (hydrate)] ;
ChemSpider	23837 ;
ECHA InfoCard	100.030.028
EC Number	233-044-6;
PubChem CID	82301;
UNII	20278OEG45 ;
CompTox Dashboard (EPA)	DTXSID10275787 ;
Properties
Chemical formula	IrCl3
Molar mass	298.58 g/mol (anhydrous)
Appearance	dark green solid; hygroscopic
Density	5.30 g/cm3, solid
Melting point	763 °C (1,405 °F; 1,036 K) (decomposes)
Solubility in water	insoluble (anhydrous IrCl3), soluble (hydrated derivative)
Magnetic susceptibility (χ)	−14.4·10−6 cm3/mol
Structure
Crystal structure	Monoclinic, mS16
Space group	C12/m1, No. 12
Thermochemistry
Std enthalpy of; formation (ΔfH⦵298)	-257 kJ/mol
Hazards
EU classification (DSD) (outdated)	not listed
Flash point	non-flammable
Related compounds
Other cations	Rhodium(III) chloride
Related compounds	Platinum(II) chloride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Iridium(III) chloride is the inorganic compound with the formula IrCl₃. The anhydrous compound is relatively rare, but the related hydrate is useful for preparing other iridium compounds. The anhydrous salt is a dark green crystalline solid. More commonly encountered is the trihydrate IrCl₃(H₂O)₃.

Preparation

Iridium is separated from the other platinum group metals as crystalline ammonium hexachloroiridate, (NH₄)₂[IrCl₆], which can be reduced to iridium metal in a stream of hydrogen. The spongy Ir thus produced reacts with chlorine at 300–400 °C to give iridium(III) chloride. Like the related rhodium compound, IrCl₃ adopts the structure seen for aluminium chloride.[1]

Hydrated iridium trichloride is obtained by heating hydrated iridium(III) oxide with hydrochloric acid.

Uses

Industrially, most iridium complexes are generated from ammonium hexachloroiridate or the related chloroiridic acid (H₂IrCl₆) as these salts are the most common commercial forms of iridium chlorides.

Hydrated iridium(III) chloride is used in the laboratory for the preparation of other iridium compounds such as Vaska's complex, trans-[IrCl(CO)(PPh₃)₂].[2] Alkene complexes such as cyclooctadiene iridium chloride dimer[3][4] and chlorobis(cyclooctene)iridium dimer[4][3] can also be prepared by heating the trichloride 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).

References

Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
Vaska, L.; & DiLuzio, J. W. (1961) J. Am. Chem. Soc. 83:2784. Girolami, G.S.; Rauchfuss, T.B.; Angelici, R.J. (1999). Synthesis and Technique in Inorganic Chemistry (3rd Edn.). Sausalito:University Science Books.
Winkhaus, G.; & Singer, H. (1966). Iridium(I)-Olefinkomplexe. Chem. Ber. 99:3610–18.
Herde, J. L.; Lambert, J. C.; & Senoff, C. V. (1974). Cyclooctene and 1,5-Cyclooctadiene Complexes of Iridium(I). Inorg. Synth. 1974, volume 15, pages 18–20. doi:10.1002/9780470132463.ch5.

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[1] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[2] Vaska, L.; & DiLuzio, J. W. (1961) J. Am. Chem. Soc. 83:2784. Girolami, G.S.; Rauchfuss, T.B.; Angelici, R.J. (1999). Synthesis and Technique in Inorganic Chemistry (3rd Edn.). Sausalito:University Science Books.

[winkhaus-3] Winkhaus, G.; & Singer, H. (1966). Iridium(I)-Olefinkomplexe. Chem. Ber. 99:3610–18.

[senoffcod-4] Herde, J. L.; Lambert, J. C.; & Senoff, C. V. (1974). Cyclooctene and 1,5-Cyclooctadiene Complexes of Iridium(I). Inorg. Synth. 1974, volume 15, pages 18–20. doi:10.1002/9780470132463.ch5.