Enhanced hydrolytic activity of Cu(ii) and Zn(ii) complexes in highly cross-linked polymers

Abstract

The chelate ligand tris[(1-vinylimidazol-2-yl)methyl]amine (5) was synthesized in five steps from commercially available starting materials. Upon reaction with ZnCl₂ or CuCl₂ in the presence of NH₄PF₆, the complexes [Zn(5)Cl]PF₆ (6) and [Cu(5)Cl]PF₆ (7) were obtained. The structure of both complexes was determined by single-crystal X-ray crystallography. Immobilization of 6 and 7 was achieved by co-polymerization with ethylene glycol dimethacrylate. The supported complexes P6-Zn and P7-Cu were found to be efficient catalysts for the hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) at 50 °C. At pH 9.5, the heterogeneous catalyst P7-Cu was 56 times more active than the homogeneous catalyst 7. Partitioning effects, which increase the local concentration of BNPP in the polymer, are shown to contribute to the enhanced activity of the immobilized catalyst.