The inorganic nitrosyl (NO(+)) complexes [Fe(CN) 5NO](2-), [Ru(bpy)2(NO)Cl](2+), and [IrCl 5(NO)](-) are useful reagents for the nitrosation of a variety of organic compounds, ranging from amines to the relatively inert alkenes. Regarding [IrCl 5(NO)](-), its high electrophilicity and inertness define it as a unique reagent and provide a powerful synthetic route for the isolation and stabilization of coordinated nitroso compounds that are unstable in free form, such as S-nitrosothiols and primary nitrosamines. Related to the high electrophilicity of [IrCl 5(NO)](-), an unusual behavior is described for its PPh 4(+) salt in the solid state, showing an electronic distribution represented by Ir(IV)-NO(*) instead of Ir (III)-NO(+) (as for the K(+) and Na(+) salts).