Complexes of N-hydroxyphthalimide and cobalt(II) acetate in reactions of alkylarene oxidation by molecular oxygen

The synergetic effect of the catalytic system cobalt(II) acetate-N-hydroxyphthalimide (NHPI) was studied in acetic acid during the oxidation of alkylbenzenes. The formation of complex between the components of catalytic system NHPI and Co(II) was demonstrated with the use of 1H NMR spectroscopy. It was established that N-hydroxyphthalimide is included in the complex as a ligand substituting for acetic acid in the internal coordination sphere of the metal; the reaction of NHPI with cobalt ions in the internal sphere leads to the formation of phthalimide-N-oxyl radicals that than participate in the catalytic cycle of the oxidation of organic substrates. The stability constants of complexes of NHPI with cobalt acetate were determined, as were those for the outer-sphere complexes of alkylbenzenes with metallocomplex.