Ethylene homo- and copolymerization catalyzed by vanadium, zirconium, and titanium complexes having potentially tridentate Schiff base ligands

Copolymerization of Ethylene with Selected Vinyl Monomers Catalyzed by Group 4 Metal and Vanadium Complexes with Multidentate Ligands: A Short Review

“…When the zirconium Zr-8 and titanium Ti-12 complexes bearing potentially tridentate phenoxy-imine ligands were employed in ethylene/1-octene copolymerization in the presence of MMAO, their activities were very high (≈12,300 kg/[mol Zr •h]) and moderate (≈450 kg/[mol Ti •h]). However, their comonomer incorporation abilities were very low (up to 0.1 mol%) and low (up to 1.5 mol%), respectively [37]. When activated with Al(iBu) 3 /Ph 3 CB(C 6 F 5 ) 4 , these complexes were able to produce copolymers with higher comonomer contents (1.6 and 3.8 mol%, respectively), yet their activities were much lower.…”

“…Interestingly, the produced copolymers showed broad chemical composition distributions and very broad molecular weight distributions, as well as high molecular weights irrespective of the comonomer concentration in the feed. At the 1-octene concentration of 0.58 mol/L, Zr-8 produced copolymers with M w = 440,000 g/mol and M w /M n = 116 (trimodal distribution), whereas Ti-12 gave the product with M w = 690,000 g/mol and M w /M n = 26.5 (bimodal distribution) [37].…”

“…Moreover, the steric hindrance of the ligand and the electron-withdrawing effect of the ligand was also unfavorable for 1-hexene insertion. The vanadium complexes V-20 and V-21 (Figure 5), activated either with EtAlCl2 or with Et2AlCl, were also examined in ethylene/1-octene copolymerization [37]. The copolymerization tests were carried out in the presence of ETA at 60 °C, for 20 min, under 5 bar ethylene, and in the presence of 2, 5, and 6.5 mL 1-octene.…”

“…When the activator was changed for Et 2 AlCl, both complexes were less active and they produced copolymers with lower comonomer contents and high dispersity (M w /M n = 6.4-7.9). The vanadium complexes V-20 and V-21 (Figure 5), activated either with EtAlCl2 or with Et2AlCl, were also examined in ethylene/1-octene copolymerization [37]. The copolymerization tests were carried out in the presence of ETA at 60 °C, for 20 min, under 5 bar ethylene, and in the presence of 2, 5, and 6.5 mL 1-octene.…”

Polymerization of α-olefins and their copolymerization with ethylene by half-sandwich scandium catalysts with an N-heterocyclic carbene ligand

“…[6][7][8][9][10] The most extensively investigated catalysts for the polymerization of α-olefins and their copolymerization with ethylene are group 4 metallocene catalysts, 2,4,10-17 constrained geometry catalysts (CGC), 3,6,7,18 and post-metallocene catalysts. 5,8,9,[19][20][21][22] Rare-earth metal catalysts have attracted a great deal of attention during the past two decades due to their unique catalytic performance in a variety of polymerization reactions of compounds such as ethylene, styrene, 1,3-conjugated dienes, polar monomers, etc. [23][24][25][26][27][28] However, most of these rare-earth metal catalysts usually show low activity or an irreversible chain termination reaction (such as β-H elimination) in α-olefin polymerization, only affording polymers with low molecular weight.…”