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

Thermal decomposition of (NH 4 ) 3 [IrCl 6 ]·H 2 O, (NH 4 ) 2 [IrCl 6 ] and (NH 4 ) 2 [IrBr 6 ] in reductive and inert atmospheres has been investigated in situ using quick-EXAFS and temperature-resolved powder X-ray diffraction. For the first time, (NH 4 ) 2 [Ir(NH 3 )Cl 5 ] and (NH 4 ) 2 [Ir(NH 3 )Br 5 ] have been proven as intermediates of thermal decomposition of (NH 4 ) 3 [IrCl 6 ]·H 2 O, (NH 4 ) 2 [IrCl 6 ] and (NH 4 ) 2 [IrBr 6 ]. Thermal degradation of (NH 4 ) 2 [IrCl 6 ] and (NH 4 ) 2 [IrBr 6 ] is a more complex process as suggested previously and includes simultaneous formation of (NH 4 ) 2 [Ir(NH 3 )Cl 5 ] and (NH 4 ) 2 [Ir(NH 3 )Br 5 ] intermediates mixed with metallic iridium. In the inert atmosphere, complexes (NH 4 )[Ir(NH 3 ) 2 Cl 4 ] and (NH 4 )[Ir(NH 3 ) 2 Br 4 ] as well as [Ir(NH 3 ) 3 Br 3 ] were proposed as possible intermediates before formation of metallic iridium particles. Decomposition of (NH 4 ) 3 [IrCl 6 ]·H 2 O, (NH 4 ) 2 [IrCl 6 ] and (NH 4 ) 2 [IrBr 6 ] has been studied. (NH 4 ) 2 [Ir(NH 3 )Cl 5 ] and (NH 4 ) 2 [Ir(NH 3 )Br 5 ] have been proposed as key intermediates in hydrogen flow. In the inert atmosphere, (NH 4 )[Ir(NH 3 ) 2 Cl 4 ] and (NH 4 )[Ir(NH 3 ) 2 Br 4 ] were found.