Bis(salicylaldiminato)titanium complexes containing bulky imine substituents: Synthesis, characterization and ethene polymerization studies

摘要

A series of titanium complexes bearing two anionic [N, O-] bidentate salicylaldiminato ligands, namely bis[(N-salicylidene) anilinato]titanium (IV) dichloride (1), bis[(N-salicylidene)2,6-dimethylanilinato]titanium(iv) dichloride (2), bis[(N-salicyhdene)-2,6-di-i- propylanilinato]titanium(iv) dichloride (3), bis[(N-salicylidene)-(1-naphthalenylimino)]titanium(iv) dichloride (4), bis[(N-salicylidene)-2,6-difluoroanilinato]titanium(iv) dichloride (5), and bis[(N-3-fluorosalicylidene)2,6-difluoroanilinato]titanium(iv) dichloride (6) have been synthesized with good yields by a two-step procedure. The X-ray structure analysis reveals that in complex 2, titanium has a distorted octahedral coordination sphere in which the oxygen atoms and the chloride ligands form the basal plane. Both the chloride and the phenoxy moieties have a cis orientation and the angle between the chloride ligands is 93.05 degrees. The imine nitrogen atoms complete the octahedral coordination of the Ti center by occupying the axial positions. The newly synthesized (2 and 4-6) and already known complexes (1 and 3) were introduced in detailed ethene-polymerization studies. The activities achieved were low to moderate depending on the size and nature of the imino substituents. The polyethenes (PEs) produced had high molar masses, and the modalities of the molecular weight distributions varyied with polymerization temperature. Based on the results of ab initio calculations and on the experimental data obtained, an explanation for uni- and bimodal polymerization behavior and the differences in catalytic activities are given. (c) Wiley-VCH Verlag GmbH & Co.