A series of novel titanium(IV) complexes bearing tetradentate [ONNO] salan type ligands: [Ti{2,2 0 -(OC 6 H 3 -5-t-Bu) 2 -NHRNH}Cl 2 ] (Lig 1 TiCl 2 : R 5 C 2 H 4 ; Lig 2 TiCl 2 : R 5 C 4 H 8 ; Lig 3-TiCl 2 : R5 C 6 H 12 ) and [Ti{2,2 0 -(OC 6 H 2 -3,5-di-t-Bu) 2 -NHC 6 H 12 NH} Cl 2 ] (Lig 4 TiCl 2 ) were synthesized and used in the (co)polymerization of olefins. Vanadium and zirconium complexes: [M{2,2 0 -(OC 6 H 3 -3,5-di-t-Bu) 2 -NHC 6 H 12 NH}Cl 2 ] (Lig 4 VCl 2 : M5 V; Lig 4 ZrCl 2 : M 5 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) 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 (Lig 1 TiCl 2 << Lig 2 TiCl 2 < Lig 3 TiCl 2 ) and declines after adding additional tert-Bu group on the aromatic rings (Lig 3 TiCl 2 < Lig 4 TiCl 2 ). 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 Et 2 AlCl-activated complexes gave polymers with lover molecular weights and bimodal distribution, whereas ultra-high molecular weight PE (up to 3588 kg mol 21 ) and narrow MWD was formed for MAO as a cocatalyst. Vanadium complex yielded PE with the highest productivity (1925.3 kg mol v 21 ), with high molecular weight (1986 kg mol 21 ) 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.

A series of new vanadium‐silsesquioxanes (2a − 2d) was prepared by reacting VCl4 with not fully condensed silsesquioxanes (having from one to four silanol groups) and evaluated as pre‐catalysts in olefin polymerization. The activation of 2a − 2d with EtAlCl2 generated highly active catalysts for ethylene polymerization, yielding high molar mass polymers with narrow dispersity. Ultra‐high molar mass polyethylenes, Mw up to 4 × 106 g mol−1, were obtained with methylaluminoxane and Al(iBu)3/[Ph3C][B(C6F5)4] as activators. Upon treatment with methylaluminoxane and boron compounds, all vanadium pre‐catalysts were active in 1‐octene polymerization as well, and produced isotactic‐rich poly(1‐octene)s with moderate monomer conversion (up to 23%). The polymerization parameters were optimized and the effect of the silsesquioxane structure on the catalytic activity and polymer properties was studied. © 2017 Society of Chemical Industry

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