Mechanistic Studies on the Reaction of [FeIII(edta)(H2O)]– with Piloty′s Acid as Source for HNO

Abstract

In earlier work performed in our laboratories, the reaction of [FeII(edta)(H2O)]2– with ·NO(g) was studied as a trap for ·NO(g) and found to be very efficient with a formation constant of ca. 106 M–1 at 25 °C. The formed nitrosyl complex was shown to have substantial FeIII‐NO–, i.e. nitroxyl, character in line with detailed computational studies performed before. In recent years, we developed an interest in the chemistry of HNO/NO– (nitroxyl) and decided to use [FeIII(edta)(H2O)]– as starting material to see whether the reaction of this complex would lead directly to the formation of the nitroxyl complex by using a source for HNO. In the present study, Piloty's acid (benzenesulfonylhydroxamic acid) was used as source for HNO, since it cleanly hydrolysis in basic aqueous solution to release HNO. The results of our studies clearly indicate that the same reaction product as found for the reaction of [FeII(edta)(H2O)]2– with ·NO(g), was formed in the reaction of [FeIII(edta)(H2O)]– with Piloty's acid. A detailed spectroscopic and mechanistic study of the latter reaction is reported.