A new principle for improving the catalytic activity of the classical complexes CuCl2-aliphatic amines used for the oxidative coupling of 2,6-dimethylphenol (DMP) is presented. It is based on the “trans” effect, typical of the substitution reactions of ligands in the square planar complexes of platinum(II). Thus, by replacing a Cl−anion with a strong “trans” effect-giving ligand such as NO2−, CN−, RS−,, a significant increase in the rate of oxidative coupling of 2,6-DMP is observed. It was quantitatively estimated by measuring the oxygen absorption rate. The highest reaction rates are given by complexes having CUS bonds (mercap-tides, thiophenolates, thiosulfates). These bonds, which probably have a high oxygen affinity, are typical for copper-containing enzymes (laccase, tyrosinase, ascorbic acid oxidase), redox enzymes that catalyze the oxidative coupling of some natural phenols very efficiently.