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

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,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 TiCl 4 . 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 × 10 6 g/molTi·h versus 72 × 10 6 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%).

The structural diversity of heterocycle-fused potassium cyclopentadienides

“…Using correlation NMR techniques, we accomplished complete signal assignment in 1 H and 13 C NMR spectra of 5-8 (see Section S1 in the ESI †). We conclude that the values of 13 C NMR chemical shis related to C(H) carbon atom correlate to electron density in the C 5 fragment of the cyclopentadienide anion. In comparison with such values in cyclopentadienides and uorenides, the chemical shis for heterocycle-fused cyclopentadienides 5-8 are substantially lower ( Table 1).…”

“….56 (t, 1H, 3 J HH ¼ 6.9 Hz), 6.68 (m, 1H), 7.21 (t, 1H, 3 J HH ¼ 6.9 Hz), 7.29 (t, 1H, 3 J HH ¼ 7.5 Hz), 7.37 (t, 1H, CH Ar , 3 J HH ¼ 7.4 Hz), 7.49 (d, 1H, CH Ar , 3 J HH ¼ 7.4 Hz), 7.55 (t, 1H, CH Ar , 3 J HH ¼ 7.9 Hz), 7.67 (d, 1H, CH Ar , 3 J HH ¼ 8.1 Hz), 7.76 (m, 4H). 13 Fig. S1 and S2 in the ESI †).…”

“…Such ligands have been successfully applied in the design of an effective epoxidation catalyst; 9 sandwich and half-sandwich complexes of group 4 metals (so-called "heterocenes") represent next-generation metallocene catalysts for a-olen polymerization. [10][11][12][13][14][15] Recently, we demonstrated the high efficiency of cyclopenta[b] thiophene Zr complexes in oligomerization of C 6 -C 10 a-olens, 16 and the promising catalytic properties of Zr ansa-complexes based on cyclopenta[1,2-b:4,3-b 0 ]dithiophene, indeno [1,2-b] indole and indeno [2,1-b]indole (Scheme 2, top) in polymerization of 1-octene. 17 In our experiments, heterocenes outperformed traditional cyclopentadienyl, indenyl and uorenyl sandwich Scheme 1 Donor heterocyclefused cyclopentadienes.…”

“…This journal is © The Royal Society of Chemistry 2019 RSC Adv., 2019, 9, 29195-29204 | 29201 -CH 2 -O-), 68.39 (-CH 2 -CH 2 -O-), 82.44 (CH Ar ), 116.66 (CH Ar ), 119.40, 123.75, 126.56 (seeFig. S3-S6 1 H, 13 C{ 1 H}, 1 H-13 C HSQC and 1 H-13 C HMBC NMR spectra in the ESI †).Synthesis and crystallization of 6. A solution of BnK (66 mg, 0.51 mmol) in THF (5 mL) was added to a stirred solution of 2 (110 mg, 0.50 mmol) in THF (10 mL).…”

Straightforward Design for Phenoxy-Imine Catalytic Activity in Ethylene Polymerization: Theoretical Prediction

“…As an inexpensive material, polyethylene (PE) has drawn significant attention due to its excellent physical properties, such as high mechanical strength, high elasticity and high resistivity towards corrosion, light weightness, and reusability [1][2][3][4]. Normally, the polyethylene materials are prepared via the coordination polymerization using different categories of catalysts, among which metallocenes are very promising candidates that provide high activity and selectivity [5][6][7][8][9][10][11]. Many experimental and theoretical methodologies show that the structures of the metallocenes determine their macroscopic properties and catalytic behaviors.…”