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A seriesof asymmetric formamidine ligands bearing different substituents withvarious steric and electronic properties on the nitrogen of the N–C–N motif were synthesized. Group 4 bis(formamidinate)dimethylamido, chloride, and benzyl complexes were studied using theseasymmetric ligands and their solid-state structures and their behaviorin solution were determined. These complexes were activated with MAO(methylalumoxane) or a combination of cocatalysts and tested in thepolymerization of ethylene and propylene. A noticeable influence ofthe formamidine nitrogen substituents on the activity of the catalystand properties of the obtained polymers was observed. Further, a plausiblemechanism for the polymerization of propylene is presented derivedfrom a combination of ESR-C60and MALDI-TOF trapping experimentswhich shed light on the nature of the active catalytic species. [ABSTRACT FROM AUTHOR]

The steric properties of variousnitrogen substituents on amidineswere tuned in order to obtain group 4 mono- and bis(amidinate) dimethylamidoor chloride complexes. The amidinate dimethylamido and chloride complexeswere prepared, and their solid-state as well as their solution-statestructures were studied. After the activation by MAO, these complexeswere tested in the polymerization of propylene and ethylene. A noticeableinfluence of the amidine carbon and nitrogen substituents on the activityof the catalyst and properties of the obtained polymer was observed.Further, a plausible mechanism for the ethylene polymerization processis presented taking into account a combination of ESR-C60and MALDI-TOF experiments, shedding light on the nature of the catalyticspecies. [ABSTRACT FROM AUTHOR]