EPR and H-1 NMR spectroscopic characterization of the ferric species formed in the iron picolinate/(pyridine/acetic acid)/HOOH catalytic system for the direct ketonization of methylenic carbons

Using EPR and H-1 NMR spectroscopy, ferric species formed in the iron picolinate/(pyridine/acetic acid)/HOOH catalytic system for the direct ketonization of methylenic carbons were characterized. The initial complex K[Fe-II(PA)(3)] (PA-pyridine-2-carboxylato) converts into mononuclear hydroxo complex Fe-III(PA)(2)(OH)Py via interaction with equimolar amount of HOOH in 2.1 Py/AcOH molar mixture. Addition of the great excess of HOOH to the solution of Fe-III(PA)(2)(OH)Py in 2:1 Py/AcOH at 253 K gives rise to the formation of the unstable high-spin ferric peroxo complex with suggested structure Fe-III(PA)(2)(OOH)Py, This complex is supposed to be reactive intermediate of oxidation.