NO+, NO, NO−! Nitrosyl siblings from [IrCl5(NO)]−

Pentachloronitrosyliridate(III) ([IrCl5(NO)]−), the most electrophilic NO+ known to date, can be reduced chemically and/or electrochemically by one or two electrons to produce the NO and HNO/NO− forms. The nitroxyl complex can be formed either by hydride attack to the NO+ in organic solvent, or by decomposition of iridium-coordinated nitrosothiols in aqueous solutions, while NO is produced electrochemically or by reduction of [IrCl5(NO)]− with H2O2. Both NO and HNO/NO− complexes are stable under certain conditions but tend to labilize the trans chloride and even the cis ones after long periods of time. As expected, the NO+ is practically linear, although the IrNO moiety is affected by the counterions due to dramatic changes in the solid state arrangement. The other two nitrosyl redox states comprise bent structures.