The steric properties of various nitrogen substituents on amidines were tuned in order to obtain group 4 mono- and bis(amidinate) dimethylamido or chloride complexes. The amidinate dimethylamido and chloride complexes were prepared, and their solid-state as well as their solution-state structures were studied. After the activation by MAO, these complexes were tested in the polymerization of propylene and ethylene. A noticeable influence of the amidine carbon and nitrogen substituents on the activity of the catalyst and properties of the obtained polymer was observed. Further, a plausible mechanism for the ethylene polymerization process is presented taking into account a combination of ESR-C60 and MALDI-TOF experiments, shedding light on the nature of the catalytic species.
T. Elkin, Dr. Naveen V. Kulkarni, Tumanskii, B., Botoshansky, M., Shimon, L. J. W., and Eisen, M. S., “Synthesis and Structure of Group 4 Symmetric Amidinate Complexes and Their Reactivity in the Polymerization of α-Olefins”, Organometallics, vol. 32, pp. 6337-6352, 2013.