New Cu(I) complexes with 2,2′-biquinolyl and 2,2′-quinolyl-pyridine containing polymer ligands as electrocatalysts for O 2 activation in the oxidation of aliphatic amines

Abstract

A series of polynuclear Cu(I) complexes with various types of polymer ligands containing 2,2′-biquinolyl (biQ) or 2,2′-quinolyl-pyridine (QPy) fragments in the polymer backbone was synthesized using sacrificial Cu anode. Cyclic voltammetry investigation of the obtained complexes revealed the formation of two types of Cu(I) coordination units, depending on the polymer's structure and electrolysis conditions. The first type of complexes, with only one biQ ligand per Cu(I) center, showed high oxidase activity in the air oxidation of primary and secondary amines to corresponding aldehydes with concomitant reduction of molecular oxygen to water. The reactions proceed in acetonitrile or N-methylpyrrolidone in the presence of O 2 at a potential of Cu II/Cu I electroreduction (−0.55 V vs. Ag/AgCl/KCl) with the high preparative yield and current efficiency. The possible scheme of the electrocatalytic process is discussed.