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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]

A series of titanium bis(amidinate)complexes containing pendantarms as one of the amidinate N substituents have been prepared andstudied in the polymerization of propylene after their activationwith MAO and other cocatalysts. The type of pendant arm greatly influencesthe reactivity and stereospecificity of the resulting polymers. Theeffect of the cocatalyst nature, its amount, and the time of the reactionhave a dramatic effect on the reactivity of a titanium bis(amidinate)bis(dimethylamido) precatalyst containing a furyl group at the pendantarm. [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]

Bis(amidinate) titanium and zirconium bis(dimethylamido)complexeswere prepared, and the dynamic behavior of the titanium complex containingperfluorinated amidinate ligand (11) was studied in detail.The variable-temperature NMR revealed the presence of two speciesin solution, in line with the different connection modes of the ligandto the metal center. The resulting complexes were tested as catalystsin the polymerization of propylene, and the resulting polymers wereconsistent with elastomeric high-molecular-weight atactic polypropylenes. [ABSTRACT FROM AUTHOR]