Nickel(II) complexes with mono(imino)pyrrole ligands: preparation, structure and ethylene polymerization behavior

Abstract

2015) Nickel(II) complexes with mono(imino)pyrrole ligands: preparation, structure and ethylene polymerization behavior, Journal of Coordination Chemistry, 68:23, 4212-4223, A series of unsymmetrical mono(imine)pyrroles (L1-L3) were synthesized by microwave irradiation from 2-acetylpyrrole and a series of dimethylanilines with two methyl groups at different positions on the aniline ring. A simplified synthetic method was initiated to prepare the corresponding nickel complexes NiL 2 (1-3) with direct condensation of mono(imine)pyrrole and nickel chloride. The compounds were determined using a suite of techniques (i.e. 1 H NMR, 13 C NMR, IR, EA, MS). L1-L3 and 3 were further characterized by X-ray crystal diffraction. The structure of 3 showed that the ligand chelated to nickel with 2 : 1 M ratio, in spite of a 1 : 1 rate of charge. Application of 1-3 in ethylene polymerization indicated that mono(imino)pyrrole nickel complexes showed low activities. The polymerization reaction time and temperature, as well as the ligand structure, influenced the catalytic performance to some extent. Experimental data showed higher activity as -CH 3 on the aniline ring is closer to the imine group.