Synthesis and structural characterization of [(dpca)MX2] (M = Cu, X = Cl; M = Cd, X = Br and M = Zn, X = NO3) complexes containing N,N-di(2-picolyl)cyclohexylamine (dpca) and their application to methyl methacrylate polymerization

A novel series of [(dpca)MX2] (M = Cu, X = Cl; M = Cd, X = Br and M = Zn, X = NO3) complexes were synthesized through the reaction of N,N-di(2-picolyl)cyclohexylamine (dpca) with the corresponding metal starting materials. X-ray crystallographic analysis determined that the metal center in complexes [(dpca)CuCl2], [(dpca)CdBr2] and [(dpca)Zn(NO3)2] showed a distorted 5-coordinated square pyramidal, trigonal bipyramidal, and 7-coordinated pentagonal bipyramidal geometry, respectively, involving coordination of the nitrogen atom of the cyclohexylamine moiety with the metal center. Specifically, the catalytic activity of [(dpca)Zn(NO3)2] (1.04 × 105 g PMMA/mol Zn·h) for the polymerization of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) at 60 °C was six-fold higher than the reference complex [ZnCl2] (1.73 × 104 g PMMA/mol Zn·h).