Iridium

Iridium metal is resistant to acids, including aqua regia.

Iridium react with O₂ when heated.

Ir(s) + O₂(g) IrO₂(s) [black]

Iridium metal reacts with fluorine forming iridium(VI) fluoride, IrF₆, and a minor amount of iridium(III) fluoride, IrF₃. Carefully heated, iridium(VI) fluoride will form the yellow tetrameric structure [IrF₅]₄.

3 Ir(s) + 6 F₂(g) IrF₆(s) [yellow] + 2 IrF₃(s) [black]
IrF₆(s) [IrF₅]₄ [yellow]


Iridium reacts with Cl₂, Br₂ and I₂, under dry conditions, forming the corresponding iridium(III) halides

2 Ir(s) + 3 Cl₂(g) 2 IrCl₃(s) [red]
2 Ir(s) + 3 Br₂(g) 2 IrBr₃(s) [red-brown]
2 Ir(s) + 4 I₂(g) 2 IrI₃(s) [dark brown]

Iridium does not react with water under normal conditions.