Preparation of Thiophene-Fused and Tetrahydroquinoline-Linked Cyclopentadienyl Titanium Complexes for Ethylene/α-Olefin Copolymerization

Author： Kim Sung Hun Park Ji Hae Song Bo Geun Yoon Seung-Woong Go Min Jeong Lee Junseong Lee Bun Yeoul

Publisher： MDPI

E-ISSN： 2073-4344|3|1|104-124

ISSN： 2073-4344

Source： Catalysts, Vol.3, Iss.1, 2013-02, pp. : 104-124

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Abstract

A synthetic scheme was developed for the large-scale preparation of a dimethylthiophene-fused and tetrahydroquinaldine-linked dimethylcyclopentadienyl titanium complex (2), which is a high-performance homogeneous Ziegler catalyst. 2,3,4,5-Tetramethyl-4,5-dihydrocyclopenta[b]thiophen-6-one was prepared without chromatography purification on the 40-g scale in a laboratory setting, from which the ligand precursor for 2 was obtained in 65% yield on a 50-g scale in a one-pot without the need for chromatography purification. Metallation was achieved in a high yield (78%) through reaction of the dilithiated compound with TiCl₄. Many derivatives were prepared by employing the same synthetic scheme as applied for 2. Among them, the titanium complex prepared from 2-methyl-4,5-dimethyl-6-(2-n-butyl-2,3,4,5-tetrahydroquinolin-8-yl)-4H-cyclopenta[b]thiophene exhibited an exceptionally high activity. Under commercially relevant high-temperature polymerization conditions (160 °C), this compound showed a higher activity than 2 (126 × 10⁶ g/molTi∙h versus 72 × 10⁶ g/molTi∙h), albeit with the formation of a polymer of slightly lower molecular weight (M_w, 159,000 versus 218,000) and with a slightly lower 1-octene content (9.3 mol% versus 12 mol%).