STEREOCHEMICAL FACTORS AND THE CATALYTIC ACTIVITY OF TRICYCLIC CU(II)COMPLEXES WITH TETRAAZA CHELATE CORES

The catalytic activity of tricyclic Cu(II) complexes with tetradentate Schiff bases based on o-aminobenzaldehyde, 1,2-ethylenediamine (I), o r 1,4-tetramethylenediamine (II) was studied in the model liquid-phase reaction of cyclohexene oxidation by molecular oxygen. The Schiff bas es had tetraaza chelate cores with square-planar and pseudotetrahedral structures. The initial catalytic activity increased when the square- planar structure changed to distorted tetrahedral as agrees with the g eneral trend of allied Cu(II) complexes with bis(oxa, aza) chelate cor es. Comparison of the catalytic behavior of Cu(II) chelates of similar spatial structure having different ligand-binding atoms points to the absence of the influence of close neighborhood on the mechanism of cy clohexene oxidation. Chelates with tetraaza cores exhibited higher cat alytic activity. In the presence of the square-planar chelate I, the r ate of cyclohexene oxidation is not stationary. This property distingu ishes I from similar Cu(II) chelates with tetradentate Schiff bases, e naminoketones, or hydrazone imines. The nonstationary oxidation of cyc lohexene in the presence of complex II agrees with the model of the ro tational isomerization of chelate core, which was discovered earlier f or distorted tetrahedral complexes.