Homo- and Heteroligated Salicylaldiminato Titanium Complexes with Different Substituents Ortho to the Phenoxy Oxygens for Ethylene and Ethylene/1-Hexene (Co)polymerization

Enhancement of Ethylene and Ethylene/1-Hexene (Co)polymerization Activities by Titanium(IV) and Zirconium(IV) Complexes Bearing Constrained Hydroxyindanone-Imine Ligands

A new series of catalysts for ethylene and ethylene/1-hexene (co)polymerizations bearing constrained hydroxyindanone-imine ligands was developed for titanium(IV) and zirconium(IV) metals with variations of steric and electronic contributions on the ligands. X-ray crystal structures revealed significantly higher open space for the constrained titanium and zirconium complexes, compared to the conventional FI counterparts. Upon activation with MAO, significantly higher ethylene polymerization activities (up to 379.4 kg-PE/mmol-M h for Zr) and notably almost doubled 1-hexene content in the ethylene/1-hexene copolymerizations were observed as a result of the constrained five-membered ring backbone.

Synthesis of Brominated Polyethylene by Copolymerization of Ethylene with ω–bromoalkene Catalyzed by a Metallocene and Methylaluminoxane System

The metallocene-catalyzed copolymerization of ethylene and 11–bromo–1–undecene was carried out to synthesize brominated polyethylene (PE). A modified methylaluminoxane (MMAO) solution was used as a cocatalyst and rac–Et(H4Ind)2ZrCl2 as a catalyst. The copolymerization showed a high activity and afforded the copolymer with a 11-bromo-1-undecene incorporation ranging from 1.0 to 4.3 mol%. When using a dried methylaluminoxane (dMAO) as a cocatalyst, the incorporation ratio of 11-bromo-1-undecene increased remarkably to 25.2 mol%. It was demonstrated that the type of MAO used as a cocatalyst affects the composition of the ethylene/11-bromo-1-undecene copolymer without changing the structure of the catalytic complex.

Bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups: crystal structure and their catalytic properties toward (co)polymerization of norbornene and 1-hexene

Eight bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups (Ni1–Ni8), Ni{(3-R₁)(5-R₂)C₆H₂(O)CHNCH(C₆H₅)₂}₂, (R₁ = H, R₂ = H, Ni1; R₁ = H, R₂ = CH₃, Ni2; R₁ = H, R₂ = OCH₃, Ni3; R₁ = H, R₂ = Br, Ni4; R₁ = CH₃, R₂ = H, Ni5; R₁ = OCH₃, R₂ = H, Ni6; R₁ = Br, R₂ = Br, Ni7; R₁ = Cl, R₂ = Cl, Ni8), were synthesized and their crystal structures were characterized using single crystal X-ray diffraction. The results revealed that Ni1–Ni6 belong to the monoclinic system (space group P2(1)/n), Ni7 belongs to the monoclinic system (space group C2/c) and Ni8 belongs to the triclinic system (space group P1̄). All nickel complexes exhibited high activities (0.46–2.07 × 10⁶ g_polymer mol_Ni⁻¹ h⁻¹) toward norbornene homopolymerization, and a strong electron-withdrawing group on the salicylaldimino aromatic ring can enhance the catalytic activity and favor polymerization. Ni1 and Ni2 exhibited high activities (0.55–2.40 × 10⁵ g_polymer mol_Ni⁻¹ h⁻¹) toward copolymerization of norbornene and 1-hexene in the presence of B(C₆F₅)₃. The 1-hexene content in the copolymers could be controlled up to 7.98–12.50% by varying the comonomer feed ratio of 1-hexene from 10 to 50%. It is observed that when the 5-position of the salicylaldimino aromatic ring has a substituent (–CH₃), the 1-hexene insertion rate is lower than that without a substituent. In addition, the polymers showed high molecular weights (1.5–2.4 × 10⁵ g mol⁻¹) and narrow molecular weight distributions (1.62–1.89). The obtained polymers were also verified to be amorphous copolymers and had high thermal stability, good solubility and optical transparency.

Ni(ii) complexes were successfully synthesized and characterized, and were highly active toward (co)polymerization of norbornene, and the 1-hexene content could be controlled.