Three Redox States of Nitrosyl: NO+, NO., and NO-/HNO Interconvert Reversibly on the Same Pentacyanoferrate(II) Platform

Abstract

Not so elusive: [FeII(CN)5(HNO)]3- has been characterized spectroscopically after the two-electron reduction of nitroprusside (see scheme). The complex is stable at pH 6, slowly decomposing to [Fe(CN)6]4- and N2O. It is deprotonated at increasing pH value with oxidation of bound NO- to [Fe II(CN)5(NO)]3-. [FeII(CN) 5 (HNO)]3- is the first non-heme iron-nitroxyl complex prepared in aqueous solution that is reversibly redox-active under biologically relevant conditions. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.