The reactions of the iron complexes (tet a)Fe II (OTf) 2 and (tet b)Fe II (OTf) 2 (tet = 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane) with dioxygen were investigated. While (tet b)Fe II (OTf) 2 undergoes slow oxidation to an iron(III) compound without detectable intermediates, (tet a)Fe II (OTf) 2 initially formed a superoxido complex which subsequently converted into the corresponding iron–oxido complex. Although attempts to structurally characterize (tet a)Fe IV (O)(OTf)(OTf) were unsuccessful, the complex could be characterized spectroscopically. In addition, during attempts to crystallize (tet b)Fe II (OTf) 2 , an aldol reaction of the solvent acetone was observed, yielding diacetone alcohol (DAA), which was found to coordinate to the iron complex.
Keller et al. (Fri,) studied this question.