Synthesis, characterization, and ethylene (Co)polymerization behavior of trichlorotitanium 2-(1-(arylimino)propyl)quinolin-8-olates

Zirconium and Hafnium Complexes Bearing Tridentate ONN-Ligands: Extremely High Activity toward Ethylene (Co)Polymerization

The pursuit of high-performance catalysts in the realm of polyolefins is a constant goal. In this study, a range of zirconium (1-ZrCl3, 2-ZrCl3, 3-ZrCl4, 12-Zr) and hafnium (1-HfCl3, 12-Hf) complexes featuring phenoxy-imine-amine ONN-ligands (2,6-R2-C6H3-NH-C6H4-N═CH-C6H2-3,5-tBu2-OH; 1-L: R = H; 2-L: R = F; 3-L: R = iPr) were synthesized and characterized using NMR spectroscopy, as well as single-crystal X-ray diffraction for 2-ZrCl3, 3-ZrCl4, and 12-Zr. These Zr and Hf complexes exhibited remarkable efficiency for ethylene homopolymerization and copolymerization with 1-octene when paired with MAO as the cocatalyst. Notably, the Zr complexes outperformed the Hf complexes with the same ligand, underscoring the substantial impact of the metal center on catalytic performance. The substituents and coordination modes of the ligands also exerted significant influence on the catalytic behavior, affecting both the activity and properties of the resulting polymers. Particularly noteworthy was the exceptional activity of 1-ZrCl3, achieving activity as high as 6.30 × 108 g(PE)·mol-1(Zr)·h-1 for ethylene homopolymerization and generating bi- or multimodal distribution polyethylene. The activation of 1-ZrCl3 by 5 or 20 equiv of d-MAO afforded a dinuclear Zr complex bridged by two chlorides (μ-Cl2-(1-ZrCl2)2), which was analyzed and confirmed by in situ 1H NMR spectroscopy and single-crystal X-ray diffraction.

Synthesis of Ti, Zr, and Hf complexes with a new tetra-azane ligand by one-pot HCl-elimination and their properties as catalysts for production of UHMWPE

The first example for the HCl-elimination reaction being applied in the attachment of an amido-containing ligand to Zr and Hf.

Transition metal complexes bearing tridentate ligands for precise olefin polymerization

This review covers key developments in the design of post-metallocene transition metal complexes (precatalysts) bearing tridentate chelating ligands and their application in olefin polymerization.

Synthesis and characterization of novel titanium complexes bearing [ONX]-type β-enaminoketonato ligands and their application to ethylene (co)polymerization

A series of novel titanium complexes bearing tridentate β-enaminoketonato chelating ligands of type, [R(2)NC(CF(3))C(H)CR(1)O]TiCl(3) (2a: R(1) = Ph, R(2) = -C(6)H(4)OMe(o); 2b: R(1) = Ph, R(2) = -C(9)H(6)N; 2c: R(1) = Ph, R(2) = -C(6)H(4)SMe(o); 2d: R(1) = Ph, R(2) = -C(6)H(4)SPh(o); 2e: R(1) = (t)Bu, R(2) = -C(6)H(4)SPh(o)) and [R(2)NC(R(1))C(H)C(CF(3))O]TiCl(3) (2f: R(1) = Ph, R(2) = -C(6)H(4)PPh(2)(o)) were prepared from TiCl(4) by treating with one equiv of deprotonated ligands in toluene. The reaction of 1a with equivalent of TiCl(4) in THF afforded another complex, C(6)H(4)OMeNC(CF(3))C(H)CPhO]TiCl(3)(thf) (3a), in addition to formation of the dichloride complex 4a, [C(6)H(4)(OMe)NC(CF(3))C(H)CPhO](2)TiCl(2). After deprotonation by alkali-metal hydride at -78 °C in diethyl ether, ligand 1a could react with 0.5 equiv of TiCl(4) to form the exclusive and clean dichloride complex 4a in high yield. These complexes were identified by NMR and mass spectra as well as elemental analyses. X-ray diffraction studies on these new trichloride complexes revealed a distorted octahedral coordination of the central metal with three chlorine atoms in a mer disposition. Dichloride complex 4a also adopted a distorted octahedral geometry around the titanium center. Two chlorine atoms are situated in the cis position, as seen in the bond angles for Cl(1)-Ti-Cl(2) (92.64(7)°). The O atom on the heterocyclic group was not coordinated with Ti. When activated by modified methylaluminoxane (MMAO), complexes 2a-e exhibited moderate to high activity towards ethylene (co)polymerization, giving relatively high molecular weight polymers with unimodal molecular weight distribution.