Insight into the thermal decomposition of ammonium hexahalogenoiridates(IV) and hexachloroiridate(III).

Thermal decomposition of (NH₄)₃[IrCl₆]·H₂O, (NH₄)₂[IrCl₆] and (NH₄)₂[IrBr₆] in reductive and inert atmospheres has been investigated in situ using quick-EXAFS and temperature-resolved powder X-ray diffraction. For the first time, (NH₄)₂[Ir(NH₃)Cl₅] and (NH₄)₂[Ir(NH₃)Br₅] have been proven as intermediates of thermal decomposition of (NH₄)₃[IrCl₆]·H₂O, (NH₄)₂[IrCl₆] and (NH₄)₂[IrBr₆]. Thermal degradation of (NH₄)₂[IrCl₆] and (NH₄)₂[IrBr₆] is a more complex process as suggested previously and includes simultaneous formation of (NH₄)₂[Ir(NH₃)Cl₅] and (NH₄)₂[Ir(NH₃)Br₅] intermediates mixed with metallic iridium. In the inert atmosphere, complexes (NH₄)[Ir(NH₃)₂Cl₄] and (NH₄)[Ir(NH₃)₂Br₄] as well as [Ir(NH₃)₃Br₃] were proposed as possible intermediates before formation of metallic iridium particles. [ABSTRACT FROM AUTHOR]