Highly selective ethylene trimerization catalyzed by half-sandwich indenyl titanium complexes with pendant arene groups and MAO

Zhang, Yanlu; Ma, Haiyan; Huang, Jiling

doi:10.1016/j.molcata.2013.03.005

Cited by 20 publications

(4 citation statements)

References 34 publications

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“…Although no coordination between the thiophene group and the titanium center could be observed in the solid state of titanocenes C2 and C4 , the thiophene group could coordinate to the generated low‐valence titanium species when these titanocenes were activated by MAO . We postulate that the introduction of more bulky substituents on the bridge unit might be beneficial to push the pendant thiophene group toward the titanium center and strengthen the intramolecular coordination interaction, thus improving the stability of the catalytically active species and leading to higher activity. Similar results were also observed for analogues C1 and C3 (entry 4 vs. entry 6).…”

Section: Resultsmentioning

confidence: 89%

“…Recently, many examples of half‐sandwich metallocenes bearing soft pendant donors such as S‐donor, P‐donor, alkyl and aryl groups on the Cp ring have been reported . In 2001, Hessen et al developed a series of half‐sandwich titanocenes with an arene‐pendant Cp ligand, which are excellent catalysts for ethylene trimerization after activation with methylaluminoxane (MAO).…”

Section: Introductionmentioning

confidence: 99%

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Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

Xiao

et al. 2014

Applied Organom Chemis

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A series of group 4 metallocenes (RCp)[Cp-(bridge)-(2-C 4 H 3 S)]MCl 2 [M = Ti (C1-C4); M = Zr (C5-C8)] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single-crystal X-ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1-C4 showed moderate catalytic activities and produced high-or ultra-high-molecular-weight polyethylene (M v 70.5-227.1 × 10 4 g mol À1 ). Titanocene C3 is more active and long-lived, with a lifetime of nearly 9 h at 30°C. At elevated temperatures of 80-110°C, zirconocenes C5-C8 displayed high catalytic activities (up to 27.6 × 10 5 g PE (mol Zr) À1 h À1 ), giving high-molecular-weight polyethylene (M v 11.2-53.7 × 10 4 g mol À1 ). Even at 80°C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system.

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Section: Resultsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

Xiao

et al. 2014

Applied Organom Chemis

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“…As catalytic oligomerization of ethylene typically produces a mathematical distribution of LAOs (linear α-olefins), transition-metal-catalyzed ethylene selective oligomerization has received considerable attention from the academic and industrial community. , In particular, trimerization of ethylene to 1-hexene is an area of intense research activity. , It is generally accepted that selective trimerization of ethylene to 1-hexene follows a metallacyclic route proposed by Briggs, which has been supported by experimental and theoretical studies. − This mechanism, mostly based on chromium catalysts, , titanium catalysts, , and tantalum catalysts, , is believed to involve metallacycle formation by oxidative coupling of two ethylene molecules at the metal center and then ring expansion by insertion of a third ethylene molecule to give a metallacycloheptane that eliminates 1-hexene (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Selective Co-Oligomerization of Ethylene and 1-Hexene by Chromium-PNP Catalysts: A DFT Study

Gong

Liu

et al. 2016

Organometallics

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The mechanism of selective co-oligomerization of ethylene and 1-hexene by the catalyst [CrCl3(PNPOMe)] (a, PNPOMe = N,N-bis(bis(o-methoxyphenyl)phosphine)methylamine) has been explored in detail using the density functional theory (DFT) method. The full catalytic cycles for the formation of 1-hexene and 1-decenes were calculated on the basis of the metallacyclic mechanism, and the distribution of all decene isomers was explained by locating Gibbs free energy surfaces of various pathways, which is in good agreement with the experimental results. A spin surface crossing through a minimum energy crossing point (MECP) from a sextet to a quartet surface takes place before the formation of metallacyclopentane, which opens up a much lower energy pathway and thus facilitates the following co-oligomerization reactions. It is worth noting that β-hydrogen agostic-assisted hydrogen transfer is of crucial importance for the decomposition of the metallacycle intermediates to give 1-hexene or decenes. Moreover, an analysis of the Cr–O bond distance and NBO charges indicates the important role of a hemiliable methoxy moiety, which acts as a pendant group in the co-oligomerization of ethylene and 1-hexene by CrCl3(PNPOMe) catalyst.

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“…Further processing with MAO can also yield different alkylaluminoxanes, such as MAO with volatile components removed (DMAO) [14]. These alkylaluminoxanes can exhibit different catalytic performance due to their unique properties and structures [13][14][15][16][17][18][19][20]. However, their application is too specific to apply on a large scale [8], and the activation effect of most cocatalysts is significantly lower than that of MAO.…”

Section: Introductionmentioning

confidence: 99%

Ammonium Tetrakis(pentafluorophenyl)borate: Preparation and Application in Olefin Coordination Polymerization as the Cocatalyst Compound

Wei,

Qu,

et al. 2024

Polymers

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Metallocene catalysts have attracted much attention from academia and industry for their excellent catalytic activity in the field of olefin polymerization. Cocatalysts play a key role in metallocene catalytic systems, which can not only affect the overall catalytic activity, but also have an obvious influence on the structure and properties of the polymer. Although methylaluminoxane (MAO) is currently the most widely used cocatalyst, its price increases the production cost of polyolefin materials. Ammonium tetrakis(pentafluorophenyl)borate has shown excellent performance in polymerization, being one of the best substitutes for the traditional cocatalyst MAO. Compared with the main catalyst, whose composition and structure are relatively complex, the research on cocatalyst is very limited. This review mainly introduces the research history, preparation methods, and application progress in polymerization of ammonium tetrakis(pentafluorophenyl)borate, deepening our understanding of the role of cocatalyst in polymerization, with the hope of inspiring brand-new thinking on improving and enhancing the overall performance of catalyst systems.

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Highly selective ethylene trimerization catalyzed by half-sandwich indenyl titanium complexes with pendant arene groups and MAO

Cited by 20 publications

References 34 publications

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

Selective Co-Oligomerization of Ethylene and 1-Hexene by Chromium-PNP Catalysts: A DFT Study

Ammonium Tetrakis(pentafluorophenyl)borate: Preparation and Application in Olefin Coordination Polymerization as the Cocatalyst Compound

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