THE ROLE OF CHELATE-FORMING LIGANDS IN THE GENERATION OF THE CATALYTIC FUNCTION OF CU2-PHASE OXIDATION OF CYCLOHEXENE BY MOLECULAR-OXYGEN( COMPLEXES BASED ON HYDROZONE IMINES IN LIQUID)

The dependence of the catalytic activity of bicyclic and tricyclic Cu2 + chelates based on hydrazone imines in a model reaction of liquid-pha se oxidation of cyclohexene by molecular oxygen on the donor-acceptor properties of ligands and the number of coordinating atoms of the liga nds is studied. Decreasing this number with the retention of the coord ination geometry of the chelate center results in the enhancement of t he catalytic activity of the Cu2+ chelate owing to an increase in its stereochemical lability. Introduction of different substituents (C6H5C O, CH3CO, and CF3CO) at the gamma-position of quasi-aromatic metallocy cles results in a decrease in the effective rate constants for cyclohe xene oxidation in the series C6H5CO > CH3CO > CF3CO. Cu2+ complexes wi th a tetragonal distortion based on hydrazone imines have unstable str uctures and isomerize into square-planar chelates during the catalytic oxidation of cyclohexene. ''Flattening'' of the chelate center result s in a decrease in the rate of the catalytic reaction, since the tetra hedrally distorted Cu2+ complexes are more active than their square-pl anar isomers. Kinetics of cyclohexene oxidation by molecular oxygen in the presence of stereochemically unstable Cu2+ chelates is studied, a nd effective rate constants for oxidation and relaxation times are cal cualted. The catalytic activity and relaxation times correlate with th e ''energy gap'' of Cu2+ chelates.