Catalysis of carbon tetrachloride conversion by copper complexes with monoethanolamine immobilized on the surface of silica

Abstract

The catalytic properties of silica-immobilized copper complexes with monoethanolamine in reactions of CCl₄ addition to 1-octene and combined metathesis of C-Cl and C-H bonds in the CCl₄-decane system were studied. The catalytic activity was found to be an extremal function of metal concentration. The increase of activity during the addition of CCl₄ to octene as the metal content was decreased to ~0.3 wt % can be explained by an increase in the fraction of mononuclear copper complexes of differing composition. Further changes in activity were due to the formation of metal complexes with various ligand environments. A comparison between EPR data and catalytic properties suggested that the most active catalysts contained a considerable number of divalent copper complexes with a coordination environment of four nitrogen atoms, which are more effective than oxygen at increasing electron density on copper ion; this facilitated the reduction of Cu(II) to Cu(I). The above complexes are unstable because the ligands are rigidly fixed on the surface and strained structures are formed. Ligands in the coordination sphere of the metal can be readily replaced by substrate molecules, which exhibit weak solvating power.