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 Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...

compounds. The anhydrous salt is a dark green

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

solid. More commonly encountered is the trihydrate IrCl₃(H₂O)₃.

Preparation

Iridium is separated from the other

platinum group metals The platinum-group metals (abbreviated as the PGMs; alternatively, the platinoids, platinides, platidises, platinum group, platinum metals, platinum family or platinum-group elements (PGEs)) are six noble, precious metallic elements clustered t ...

as crystalline ammonium hexachloroiridate, (NH₄)₂ rCl₆ which can be reduced to iridium metal in a stream of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

. The spongy Ir thus produced reacts with

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

at 300–400 °C to give iridium(III) chloride. Hydrated iridium trichloride is obtained by heating hydrated iridium(III) oxide with

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

Structure

Like the related rhodium compound, IrCl₃ adopts the structure seen for

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...

. This is the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

α polymorph. A

rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...

β polymorph also exists. Both polymorphs have effectively the same anion lattice but differ in the octahedral interstices the iridium ions occupy.

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 Vaska's complex is the trivial name for the chemical compound ''trans''-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO) (C6H5)3sub>2. This square planar diamagnetic organometallic complex consists of a central iridi ...

, ''trans''- rCl(CO)(PPh₃)₂Vaska, 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.

Alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

complexes such as cyclooctadiene iridium chloride dimerWinkhaus, 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. . and chlorobis(cyclooctene)iridium dimer 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 The Dangerous Substances Directive (as amended) was one of the main European Union laws concerning chemical safety, until its full replacement by the new regulation CLP Regulation (2008), starting in 2016. It was made under Article 100 (Art. 94 ...

, but is listed in the inventory of the

Toxic Substances Control Act The Toxic Substances Control Act (TSCA) is a United States law, passed by the 94th United States Congress in 1976 and administered by the United States Environmental Protection Agency (EPA), that regulates chemicals not regulated by other U. ...

(TSCA).

References

{{DEFAULTSORT:Iridium(Iii) Chloride Chlorides Iridium compounds Platinum group halides