Synthesis of Anthracene-Bridged Dinuclear Phenoxyiminato Organotitanium Catalysts with Enhanced Activity, Thermal Stability, and Comonomer Incorporation Ability toward Ethylene (Co)polymerization

Abstract

Dinuclear titanium complexes syn-Ti 2 and anti-Ti 2 bearing anthracene-bridged bisphenoxyimine ligands (syn-L and anti-L) have been prepared and characterized by NMR and elemental analyses. The molecular structure of syn-Ti 2 was defined by X-ray diffraction, revealing a separation of 7.183 Å between the two Ti centers. The mononuclear complex [(2,6-i Pr 2 -C 6 H 3 NCH-C 6 H 2 -3,5-t Bu-2-O)TiCl 3 (THF)] (Ti 1 ) was also prepared for control experiments. In the presence of MAO as a cocatalyst, syn-Ti 2 and anti-Ti 2 were active toward ethylene homopolymerization but had distinct catalytic properties. The complex syn-Ti 2 with a shorter metal−metal separation exhibited higher activity and produced polymers with higher molecular weights, in comparison to anti-Ti 2 , having a longer metal−metal separation, and the mononuclear catalyst control Ti 1 under identical conditions. More importantly, the complex syn-Ti 2 exhibited excellent thermal stability and thus the a greater activity can be obtained at 100 °C, which is a preferred temperature for industrial operations. For ethylene/1-hexene copolymerization, the activity, M w , and incorporation of 1-hexene by syn-Ti 2 were 2.3×, 3.2×, and 6.0× those of anti-Ti 2 under identical conditions.

Chromium complexes supported by NNO-tridentate ligands: an unprecedented activity with the requirement of a small amount of MAO

“…The conden-sation reaction was catalyzed by p-TsOH in methanol at room temperature to give the desired NNO-tridentate ligands LH1-LH6 in high yields (77-95%). 58,59 All the organic ligands were characterized by 1 H and 13 C NMR (Fig. S1-S12 †), and elemental analysis.…”

Copolymerization of Ethylene and Long-Chain Functional α-Olefins by Dinuclear Zirconium Catalysts

“…Multimetallic catalysts have been pursued as a method for synthesizing functionalized polyethylene via a direct copolymerization of ethylene and polar monomers . Examples of bimetallic catalysts with rigid linkers that feature improved performance include enhanced incorporation of functionalized norbornenes using dinickel catalysts ( A ; Figure ), higher incorporation of ester-containing comonomers and acrylic anhydride using macrocyclic frameworks to support “double-decker” dinickel or dipalladium catalysts with phenoxy-imine ( B ) or α-diimine ( C ) donors, − and increased tolerance to amine additives and incorporation of amino olefins by terphenyl-supported bis­(phenoxy-imine)­dinickel catalysts ( D ). − Bimetallic catalysts displaying early transition metals have been demonstrated to affect performance by increasing the incorporation of α-olefins ( E and F ), − though not those containing polar groups. A bimetallic mechanism of α-olefin incorporation was proposed where distal C–H bonds interact with the second metal to facilitate enchainment. − ,− An analogous bimetallic mechanism for comonomer incorporation is particularly appealing for polar olefins.…”

Synthesis of Ethylene/1-Octene Copolymers with Ultrahigh Molecular Weights by Zr and Hf Complexes Bearing Bidentate NN Ligands with the Camphyl Linker

“…In both 1 H and 13 C NMR spectra, each pair of substituents on the N atoms exhibits two characteristic sets of resonances, suggesting a C1-symmetric structure due to the unsymmetric camphyl backbone. The broad signals at 3.53 and 1.08 ppm (Figure S1), whose integrations correspond to four protons, indicate the presence of one coordinated THF molecule [53]. Furthermore, the distinct ene-diamido characteristics was determined by the X-ray analyses of 1-Zr and 1-Hf.…”