Synthesis, characterization and activity of a novel CGC-type Group 4 metallocenes - дипломная работа | ИСТИНА – Интеллектуальная Система Тематического Исследования НАукометрических данных

Научный руководитель: Borzov Maxim V.
Автор: Sun Qi
Тип: Специалист
Организация, в которой проходила защита: College of Chemistry and Material Science, the North-West University of Xi’an, Taibai Bei Avenue 229, Xi’an 710069, Shaanxi Province, People’s Republic of China
Год защиты: 2010
Аннотация: Since the development of Zeigler-Natta catalysts, a tremendous amount of the research efforts have been focused on catalysts and catalytic systems for olefin polymerization, copolymerization and oligmerization. Among all types of these catalysts, the so-called "constrained geometry" metallocene-type catalysts (CGC-s) (entered first into practice by DOW company) exhibit top-advantageous characteristics for production of polyolefins of regulated tacticity. The initial idea of this Master Degree work, actually, lays in the CGC chemistry area and, namely, is to introduce the novel 1-methyl-lH-imidazolyl side-chain functionalized cyclopentadienes as ligands into the organochemistry of the Group 4 elements (Ti and Zr) and to study the catalytic activity of the resultant complexes for olefin polymerization. The present investigation naturally comprises three interconnected parts. At the first stage, we have developed synthetic approaches to target 2-[(cyclopentadienyl)diphenylmethyl]- and 2-[(cyclopentadienyl)phenylmethyl]-1-methyl-1H-imidazoles (denoted as 3a and 3b in the body of the manuscript) by reactions of 2-lithio-1-methyl-1H-imidazole with 6,6-diphenyland/or 6-phenylfulvenes. Compounds 3a and 3b have been fully characterized by appropriate instrumental methods and have been shown to exist as mixtures of isomers (tautomers) in respect to the position of the substituent at the cyclopentadienyl ring, with the (cyclopenta-1,3-dien-2-yl) ones dominating. Occasionally, we have got managed to isolate and characterize 2-[(n-butylcyclopentadienyl)phenylmethyl]-1-methyl-1H-imidazole (4) as a side-product in one of the reaction runs. Compounds 3a and 3b have been converted into corresponding lithium cyclopentadienides (2a and 2b), with the molecular structure of the salt 2a (adduct with 2 molecules of THF) established by X-ray diffraction analysis. At the second step of the investigation, we have prepared four Ti and Zr complexes derived from cyclopentadienes 3a and 3b starting directly from lithiated forms 2a and/or 2b or via their intermediate conversion into trimethylsilylated cyclopentadienes. Crystal and molecular structure of trichloro{2-[(h5-cyclopentadienyl)diphenylmethyl]-1-methyl-1H-imidazole-kN3}(tetrahydrofuran-kO)zirconium(IV) (6a) was established by X-ray diffraction analysis. On an example of Zr-complex 6a, we have examined its catalytic activity in respect to ethylene polymerization in presence of methylalumoxane (MAO; molar ratio Al : Zr 3000). The tests revealed catalytic activity of the system of question up to 1.30*10^5 g* (mol* h)^-1. Studies of the prepared polyethylene by GPC analysis have pointed out unimodal molecular weigh distribution with moderate average weighs and small weigh dispersions. Attempts to perform polymerization tests with the silica-immobilized 6a were also undertaken.
Добавил в систему: Борзов Максим Владимирович

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Synthesis, characterization and activity of a novel CGC-type Group 4 metallocenesдипломная работа (Специалист)

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