Iridium compounds

[2][3] iridium(VIII) oxide (IrO4) was generated under matrix isolation conditions at 6 K in argon.

[2] Iridium hexafluoride, IrF6, is a volatile yellow solid, composed of octahedral molecules.

[2] Iridium pentafluoride is also a strong oxidant, but it is a tetramer, Ir4F20, formed by four corner-sharing octahedra.

Hexachloroiridic(IV) acid, H2IrCl6, and its ammonium salt are the most common iridium compounds from an industrial and preparative perspectives.

The IrCl2−6 ion has an intense dark brown color, and can be readily reduced to the lighter-colored IrCl3−6 and vice versa.

[15] Iridium trichloride, IrCl3, which can be obtained in anhydrous form from direct oxidation of iridium powder by chlorine at 650 °C,[15] or in hydrated form by dissolving Ir2O3 in hydrochloric acid, is often used as a starting material for the synthesis of other Ir(III) compounds.

In the presence of air, iridium metal dissolves in molten alkali-metal cyanides to produce the Ir(CN)3−6 (hexacyanoiridate) ion.

It forms compounds such as lithium iridate (Li2IrO3), which forms black crystals with three slightly different layered atomic structures, α, β, and sometimes γ. Lithium iridate exhibits metal-like, temperature-independent electrical conductivity,[17] and changes its magnetic ordering from paramagnetic to antiferromagnetic upon cooling to 15 K.[16] Lithium iridate is a potential electrode material for the lithium-ion battery.

Important starting reagents being hydrated iridium trichloride and ammonium hexachloroiridate.

Illustrative is the carbonylation of the trichloride: Many organoiridium(III) compounds are generated from pentamethylcyclopentadienyl iridium dichloride dimer.