Synthesis, structure, NO-donor and redox activity of bis-(2-methylfuranethiolate)tetranitrosyl diiron

Abstract

The new tetranitrosyl binuclear iron complex [Fe2(SС5H5O)2(NO)4] (I) has been synthesized by the reaction of aqueous solutions of anionic salts [Fе(S2O3)2(NO)2]3− and [SС5H5O]−. The latter one has been obtained by the reduction of methyl furfuryl disulfide by hydrazine hydrate in ethanol at T=25°C. The molecular and crystalline structure of I has been determined by X-ray method. The complex has binuclear structure of “μ-S” type with the distance between the iron atoms ∼2.70Å. In the crystalline structure shortened intermolecular contacts of the nitrosyl groups of the adjacent molecules are observed. The maximum amount of NO generated by I in 1% aqueous solution of dimethylsulfoxide (DMSO) is ∼5nM, and it reduces to zero in 8min after decomposition starts in anaerobic conditions at Т=25°С, pH 6.5. As follows from the method of natural bond orbital analysis (NBO analysis), complex I has rather strong FeNO bond, as compared to other NO donors. Using CVA method, the values of reduction potentials for I in an aprotic solvent have been determined, and the scheme for its reduction has been suggested.