Two decomposition mechanisms of nitrosyl iron complexes [Fe2(μ-SR)(NO)4]

Two decomposition mechanisms of nitrosyl iron complexes (NICs) [Fe2(μ-SR)(NO)4] in aqueous medium are known. One mechanism (for instance, in the case of complex [Fe2(μ-SC4H3N2)2(NO)4]) involves irreversible and rapid hydrolysis of NIC with the NO release accompanied with the formation of the products of further NO transformations. In the other mechanism (for instance, in the case of complexes [Fe2(μ-S(CH2)2NH3)2(NO)4]SO4• •2.5H2O and [Fe2(μ-SC5H11NO2)2(NO)4]SO4•5H2O), no hydrolysis occurs but NICs reversibly dissociate to release both NO and thiolate ligand into the medium. In the present work, the difference in the mechanisms of the NIC decomposition is explained by the difference in the NIC redox potentials. The experimental evidences of this fact are given.