THE ROLE OF CHELATE-FORMING LIGANDS IN THE GENERATION OF THE CATALYTIC FUNCTION OF CU2+ COMPLEXES BASED ON HYDROZONE IMINES IN LIQUID-PHASE OXIDATION OF CYCLOHEXENE BY MOLECULAR-OXYGENстатья
Информация о цитировании статьи получена из
Web of Science
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 29 мая 2015 г.
Аннотация:The dependence of the catalytic activity of bicyclic and tricyclic Cu2+ chelates based on hydrazone imines in a model reaction of liquid-phase oxidation of cyclohexene by molecular oxygen on the donor-acceptor properties of ligands and the number of coordinating atoms of the ligands is studied. Decreasing this number with the retention of the coordination geometry of the chelate center results in the enhancement of the catalytic activity of the Cu2+ chelate owing to an increase in its stereochemical lability. Introduction of different substituents (C6H5CO, CH3CO, and CF3CO) at the gamma-position of quasi-aromatic metallocycles results in a decrease in the effective rate constants for cyclohexene oxidation in the series C6H5CO > CH3CO > CF3CO. Cu2+ complexes with a tetragonal distortion based on hydrazone imines have unstable structures and isomerize into square-planar chelates during the catalytic oxidation of cyclohexene. ''Flattening'' of the chelate center results in a decrease in the rate of the catalytic reaction, since the tetrahedrally distorted Cu2+ complexes are more active than their square-planar isomers. Kinetics of cyclohexene oxidation by molecular oxygen in the presence of stereochemically unstable Cu2+ chelates is studied, and effective rate constants for oxidation and relaxation times are calcualted. The catalytic activity and relaxation times correlate with the ''energy gap'' of Cu2+ chelates.