Transformations of the hexanitroiridate(III) ion in chloride and hydrochloric acid solutions

N-15 NMR and electronic spectroscopy were used to study transformations of a hexanitroiridate(III) ion in neutral chloride and hydrochloric acid solut ions at 100 degrees C or at boiling. In neutral solutions, the nitrate ions are replaced by Cl- to form tetranitro, trinitro, and dinitro derivatives, among which trans-[Ir(NO2)(4)Cl-2](3-) and fac-[Ir(NO2)(3)Cl-3](3-) are th e most kinetically stable. Quantitative transformation of [Ir(NO2)(6)](3-) into hexachloro complexes in hydrochloric acid (6-12 M) solutions takes fro m 40 to 60 h. The conversion of [IrNO2Cl5](3-) into hexachloroiridate ion i s the rate-limiting step of the process. The reaction with hydrochloric aci d in the presence of urea results in fast and quantitative transformation o f [Ir(NO2)(6)](3-) into hexachloroiridate ions without the accumulation of the nitrate ions in solution.