EPR and 1H 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

Abstract Using EPR and 1 H 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.