Titanium and Zirconium Complexes Bearing a Trialkoxoamine Ligand: Synthesis and Olefin Polymerization Activity

The effect of catalyst symmetry over the stereoregularity of the polyolefins obtained and the mechanism of the polymerization were studied with various aminoalcohol based titanium and zirconium catalysts having C(3) and pseudo-C(s), symmetries. These precatalysts in combination with MAO polymerized 1-hexene in a controlled manner. The isotactic polyhexene obtained from the C(3)-symmetric titanium catalyst (1-TiCl) had molecular weight of around 46500 (pdi = 1.3) and the zirconium analogue (1-ZrCl) had the molecular weight of 53000. The hemi-isotactic polymer from the pseudo-C(s)-symmetric titanium catalyst (2-TiCl) had the molecular weight of around 617000 (pdi = 1.3) and that of zirconium analogue (2-ZrCl) had molecular weight of 626000. The catalysts prepared from a 50: 50 mixture of the aminotriols also polymerized 1-hexene and the bimodal nature of the GPC traces of the polyhexenes obtained suggests that these catalysts act independently in the mixture and also imply the absence of polymeryl transfer between the catalytic centers. In all cases, the individual catalysts apparently retain their original symmetry (C(3) or C(s)) avoiding the formation of aggregates or polymeric forms.