193672-85-4Relevant academic research and scientific papers
Olefin polymerization and copolymerization by complexes bearing [ONNO]-Type salan ligands: Effect of ligand structure and metal type (titanium, zirconium, and vanadium)
Bialek, Marzena,Pochwala, Monika,Spaleniak, Grzegorz
, p. 2111 - 2123 (2014/07/08)
A series of novel titanium(IV) complexes bearing tetradentate [ONNO] salan type ligands: [Ti{2,2′-(OC6H3-5-t-Bu) 2-NHRNH}Cl2] (Lig1TiCl2: R = C 2H4; Lig2TiCl2: R = C 4H8; Lig3TiCl2: R = C 6H12) and [Ti{2,2′-(OC6H 2-3,5-di-t-Bu)2-NHC6H12NH}Cl 2] (Lig4TiCl2) were synthesized and used in the (co)polymerization of olefins. Vanadium and zirconium complexes: [M{2,2′-(OC6H3-3,5-di-t-Bu)2-NHC 6H12NH}Cl2] (Lig4VCl2: M = V; Lig4ZrCl2: M = Zr) were also synthesized for comparative investigations. All the complexes turned out active in 1-octene polymerization after activation by MAO and/or Al(i-Bu)3/[Ph 3C][B(C6F5)4]. The catalytic performance of titanium complexes was strictly dependent on their structures and it improves for the increasing length of the aliphatic linkage between nitrogen atoms (Lig1TiCl2 2TiCl2 3TiCl2) and declines after adding additional tert-Bu group on the aromatic rings (Lig3TiCl2 4TiCl2). The activity of all titanium complexes in ethylene polymerization was moderate and the properties of polyethylene was dependent on the ligand structure, cocatalyst type, and reaction conditions. The Et2AlCl-activated complexes gave polymers with lover molecular weights and bimodal distribution, whereas ultra-high molecular weight PE (up to 3588 kg mol-1) and narrow MWD was formed for MAO as a cocatalyst. Vanadium complex yielded PE with the highest productivity (1925.3 kg mol v-1), with high molecular weight (1986 kg mol -1) and with very narrow molecular weight distribution (1.5). Copolymerization tests showed that titanium complexes yielded ethylene/1-octene copolymers, whereas vanadium catalysts produced product mixtures.
