Abstract
We synthesized a series of Me2Si-bridged ansa-zirconocene complexes coordinated by thiophene-fused cyclopentadienyl and fluorenyl ligands (Me2Si(2-R1-3-R2-4,5-Me2C7S)(2,7-R32C13H6))ZrMe2 (R1 = Me or H, R2 = H or Me, R3 = H, tBu, or Cl) for the subsequent preparation of supported catalysts. We determined that the fluorenyl ligand adopts an η3-binding mode in 9 (R1 = Me, R2 = H, R3 = H) by X-ray crystallography. Further, we synthesized a derivative 15 by substituting the fluorenyl ligand in 9 with a 2-methyl-4-(4-tert-butylphenyl)indenyl ligand, derivatives 20 and 23 by substituting the Me2Si bridge in 12 (R1 = Me, R2 = H, R3 = tBu) and 15 with a tBuO(CH2)6(Me)Si bridge, and the dinuclear congener 26 by connecting two complexes with a –(Me)Si(CH2)6Si(Me)– spacer. The silica-supported catalysts prepared using 12, 20, and 26 demonstrated up to two times higher productivity in ethylene/1-hexene copolymerization than that prepared with conventional (THI)ZrCl2 (21–26 vs. 12 kg-PE/g-(supported catalyst)), producing polymers with comparable molecular weight (Mw, 330–370 vs. 300 kDa), at a higher 1-hexene content (1.3 vs. 1.0 mol%) but a lower bulk density of polymer particles (0.35 vs. 0.42 g/mL).
Highlights
Homogeneous single-site catalysts, such as metallocene and half-metallocene, and post-metallocene catalysts are actively used in the production of polyethylene (PE) and polypropylene (PP), most PE and PP is still produced by suing heterogeneous Ziegler–Natta catalysts [1,2]
While homogeneous catalysts can be directly used in a solution process where polymers (e.g., polyolefin elastomer (POE) with high α-olefin content) are formed by dissolution in solvent, they should be immobilized on an inorganic support, e.g., silica, in order to be applied in a slurry-process or a gas-phase process, where the morphology of the generated polymer particles is of importance for stable operation [3–11]
We reported the syntheses of ansa-metallocene complexes coordinated by thiophene-fused cyclopentadienyl and tetramethylcyclopentadienyl ligands (I in Scheme 1), Catalysts 2022, 12, 283
Summary
Homogeneous single-site catalysts, such as metallocene and half-metallocene, and post-metallocene catalysts are actively used in the production of polyethylene (PE) and polypropylene (PP), most PE and PP is still produced by suing heterogeneous Ziegler–Natta catalysts [1,2]. While homogeneous catalysts can be directly used in a solution process where polymers (e.g., polyolefin elastomer (POE) with high α-olefin content) are formed by dissolution in solvent, they should be immobilized on an inorganic support, e.g., silica, in order to be applied in a slurry-process or a gas-phase process, where the morphology of the generated polymer particles is of importance for stable operation [3–11]. Other studies reported the syntheses of metallocene and half-metallocene complexes with thiophene-fused cyclopentadienyl ligands (some of which have been used for commercial processes with advantageouuss perffoorrmmaannccee)) [[2288––3333]] aanndd tthhee ssyynntthheesseess ooff ddiinnuucclleeaarr ccoomm-plexes, for the purpose of developing new polymerization catalysts [34–40]. IInn tthhiiss wwoorrkk,, we synthesized a series of silylene-bridged ansa-metallocene complexes constructed with thiophene-fused cyclopentadienyl ligands for the purpose of ppreparing high-performance ssuuppppoorrtteedd ccaattaallyyssttss,, tthhee ssuucccceessssffuull rreessuullttss ooff wwhhiicchh aarree rreeppoorrtteedd hheerreeiinn
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