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《Comptes Rendus Chimie》2008,11(3):307-316
Iron and cobalt complexes are a new family of catalysts for ethylene oligomerization and polymerization. The extensive researches on bis(imino)pyridyl metal complexes have been carried out with the aim of synthesizing their derivatives and finding suitable reaction parameters for the optimum activity. Beyond the modification works of bis(imino)pyridyl metal complexes, several alternative models with similar coordination sphere have been developed in our group. This review article describes our experiences in innovating new models of iron and cobalt complexes as catalysts for ethylene oligomerization and polymerization. 相似文献
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Bis(imino)pyridyl Fe(II) complexes are important catalysts in ethylene oligomerization for preparing α-olefins. The metal net charge-activity relationship of bis(imino)pyridyl Fe(II) complexes was investigated by molecular mechanics (MM) and net charge equilibration (QEq) method with modified Dreiding force field. It was found that metal net charge was in reverse ratio to ethylene oligomerization activity. Electron-donor substituents with less steric hindrance to the central metal were favorable to Fe complex activity. Metal net charge-activity relationship could be used to assist the design of new Fe oligomerization catalysts with higher activity. 相似文献
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Wen-Hua Sun Peng Hao Shu Zhang Jianjun Yi Ning Tang 《Journal of organometallic chemistry》2007,692(21):4506-4518
The 1-(6-(quinoxalin-2-yl)pyridin-2-yl)ethanone was synthesized in order to prepare a series of N-(1-(6-(quinoxalin-2-yl)pyridine-2-yl)ethylidene)benzenamines (L1-L7), which provided new alternative N∧N∧N tridentate ligands coordinating with iron(II) and cobalt(II) dichloride to form complexes of general formula LFeCl2 (1-7) and LCoCl2 (8-14). All organic compounds were fully characterized by NMR, IR spectroscopic and elemental analysis along with and magnetic susceptibilities and metal complexes were examined by IR spectroscopic and elemental analysis, while their molecular structures (L1, L4, 1, 4, 10, 13) were confirmed by single crystal X-ray diffraction analysis. Upon activation with methylaluminoxane (MAO), all iron complexes gave good catalytic activities for ethylene reactivity (oligomerization and polymerization), while their cobalt analogues showed moderate activities toward ethylene oligomerization with modified methylaluminoxane (MMAO). Various reaction parameters were investigated for better catalytic activities, the higher activities were observed at elevated ethylene pressure. The iron and cobalt complexes with para-methyl substituents of aryl group linked on imino group showed highest activity. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(19):5170-5181
Unique features of earth‐abundant transition‐metal catalysts are reviewed in the context of catalytic carbon–carbon bond‐forming reactions. Aryl‐substituted bis(imino)pyridine iron and cobalt dihalide compounds, when activated with alkyl aluminum reagents, form highly active catalysts for the polymerization of ethylene. Open‐shell iron and cobalt alkyl complexes have been synthesized that serve as single‐component olefin polymerization catalysts. Reduced bis(imino)pyridine iron and cobalt dinitrogen compounds have also been discovered that promote the unique [2+2] cycloaddition of unactivated terminal alkenes. Studies of the electronic structure support open‐shell intermediates, a deviation from traditional strong‐field organometallic compounds that promote catalytic C−C bond formation. 相似文献
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一种吡啶二亚胺类铁催化剂的合成及乙烯低聚研究 总被引:5,自引:0,他引:5
设计并合成了一种新型吡啶二亚胺类铁配合物 ,该配合物配体中将氟取代基和甲基取代基结合在一起 ,用于乙烯齐聚活性可以达到 10 7g molFe·h ,产物中 90 %以上是 1 丁烯 ,1 己烯和 1 辛烯等低碳数α 烯烃 .低聚反应温度对低聚活性和低聚物分布有很大影响 ,随着反应温度的提高 ,齐聚活性降低 ,低聚物明显向低碳数分布移动 .随着Al Fe的增加 ,低聚活性先迅速增加 ,在Al Fe为 10 0 0时达到最大 ,然后又迅速降低 ;低聚物的分布基本不受Al Fe的影响 .比较了几种具有相似结构的化合物及其低聚性能与新合成的催化剂 ,讨论了配合物结构与低聚活性和低聚物性能之间的关系 .合适的邻位取代基位阻和取代基电子效应是决定催化剂活性和低聚物分布的主要因素 . 相似文献
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Rubin Huang Cor E. Koning John C. Chadwick 《Journal of polymer science. Part A, Polymer chemistry》2007,45(17):4054-4061
The effects of hydrogen in ethylene polymerization and oligomerization with different bis(imino)pyridyl iron(II) complexes immobilized on supports of type MgCl2/AlEtn(OEt)3–n have been investigated. Hydrogen has a significant activating effect on polymerization catalysts containing relatively bulky bis(imino)pyridyl ligands, but this is not the case in ethylene oligomerization with a catalyst containing relatively little steric bulk in the ligand. It was found that the presence of hydrogen in the latter system led to decreased activity and an overall increase rather than a decrease in product molecular weight, indicating deactivation of active species producing low molecular weight polymer and oligomer. Decreased formation of vinyl‐terminated oligomers in the presence of hydrogen can therefore contribute to the activating effect of hydrogen in ethylene polymerization with immobilized iron catalysts, if it is assumed that hydrogen activation is related to chain transfer after a 2,1‐insertion of a vinyl‐terminated oligomer into the growing polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4054–4061, 2007 相似文献
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Rubin Huang Nileshkumar Kukalyekar Cor E. Koning John C. Chadwick 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):135-143
Ethylene polymerizations carried out with various bis(imino)pyridyl iron, chromium and vanadium complexes immobilized on a MgCl2/AlRn(OEt)3−n support gave relatively broad polyethylene molecular weight distributions in the case of iron, but high molecular weight and a very narrow molecular weight distribution with vanadium, indicative of a single active species. The narrow MWD was confirmed by melt rheometry. Similar results were obtained after reaction of the bis(imino)pyridyl complex LVCl3 (6) with MeLi or AlEt3, where alkylation of the pyridine ring gives a complex L′VCl2 (7). In the case of chromium, a bimodal distribution was obtained, with evidence of incomplete catalyst immobilization. The polyethylene molecular weights obtained with the iron complexes were strongly dependent on the substituents in the bis(imino)pyridyl ligand, and were somewhat higher than have been obtained in homogeneous polymerization. In contrast, the molecular weights obtained with the bis(imino)pyridyl chromium and vanadium complexes were much higher that those previously obtained under homogeneous conditions. In all cases, the activities of the immobilized catalysts were higher than those found in homogeneous polymerization. 相似文献
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A series of 2,6-bis(imino)pyridyl iron and cobalt complexes bearing p-substituent [2,6-(ArN=CMe)2C5H3N]- MCl2 (Ar=2,6-Me2C6H3, 2,4,6-Me3C6H2, 2,6-Me2-4-BrC6H2, 2,6-Me2-4-ClC6H2, 2,4-Me2-6-BrC6H2, 2,4-Me2-6- ClC6H2, while M=Fe, Co) have been synthesized and investigated as catalysts for ethylene polymerization in the presence of modified methylaluminoxane as a cocatalyst. The electron effect and positions of the substituent of pyridinebisimine ligands were observed to affect considerably catalyst activity and polymer property. 相似文献
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应用金属原子净电荷相关性(MANCC)方法研究了铁(Ⅱ)类催化剂活性. 取代基的电子效应占主导作用的催化剂, 活性与中心金属原子净电荷有较好的相关性. 当取代基呈供电子效应时, 催化剂活性随着电荷的增大而升高, 当取代基呈吸电子效应时, 催化剂活性随着电荷的增大而降低. 在此基础上推测烯烃聚合反应催化过程中可能存在两种不同的活性中心, 一种是[LFe-R]+, 另一种是[LFe-R]2+或[Fe(Cl)RL]+. 当取代基的电子效应和空间效应均对活性有影响时, 发现催化剂的两卤素净电荷差值越小, 催化活性越强. 相似文献
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利用乙烯常压聚合原位紫外 可见 (UV Vis)光谱技术 ,对 3个铁、钴络合物作为催化剂前体的催化剂体系进行了研究 .3个铁、钴络合物分别为 2 ,6 双 [1 (2 ,6 二甲基苯基亚胺 )乙基 ]吡啶二氯化铁 (a)、2 ,6 双 [1 (2 ,4,6 三甲基苯基亚胺 )乙基 ]吡啶二氯化铁 (b)和 2 ,6 双 [1 (2 ,6 二异丙基苯基亚胺 )乙基 ]吡啶二氯化钴(c) .实验结果表明 ,MAO对络合物催化剂前体的活化作用是一个快速过程 ;在聚合条件下分别观察到 5 6 0、6 30和 5 80nm的活性峰 ,考察了它们在聚合过程中的生长和在加入无水乙醇逐步使催化剂中毒时活性峰的消失规律 .对催化剂活性物种的结构和聚合机理进行了探讨 相似文献
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The unsymmetric precursor ethyl 6-acetylpyridine-2-carboxylate (4) was synthesized from 2,6-dimethylpyridine (1). On the basis of this precursor, a new mono(imino)pyridine ligand (5) and the corresponding Co(Ⅱ) complex {2-carbethoxy-6-[1-[(2,6-diethylphenyl)imino]ethyl]pyridine}CoCl2 (6) were prepared. The crystal structure of complex indicates that the 2-carbethoxy-6-iminopyridine is coordinated to the cobalt as a tridentate ligand using [N, N, O] atoms, and the coordination geometry of the central cobalt is a distorted trigonal bipyramid, with the pyridyl nitrogen atom and the two chlorine atoms forming the equatorial plane. Being applied to the ethylene oligomedzation, this cobalt complex shows catalytic activity of 1.820× 10^4 g/mol-Cooh at 101325 Pa of ethylene at 15.5℃ for 1 h, when 1000 equiv, of methylaluminoxane (MAO) is employed as the cocatalyst. 相似文献
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Nobbs JD Tomov AK Cariou R Gibson VC White AJ Britovsek GJ 《Dalton transactions (Cambridge, England : 2003)》2012,41(19):5949-5964
A series of bis(thiazolinyl)- and bis(thiazolyl)pyridine Thio-Pybox ligands and their metal complexes of chromium(III), iron(II), cobalt(II) and nickel(II) has been prepared, as well as a nickel(II) complex containing a monoanionic bis(thiazolinyl)phenyl Thio-Phebox ligand. These new metal complexes have been characterised and used as catalysts, in combination with the co-catalyst MAO, for the polymerisation of ethylene and for the polymerisation of butadiene. In the case of ethylene polymerisation, the Thio-Pybox and Thio-Phebox metal complexes have shown relatively low polymerisation activities, much lower compared to the related bis(imino)pyridine complexes of the same metals. In the polymerisation of butadiene, several Thio-Pybox cobalt(II) complexes show very high activities, significantly higher than the other metal complexes with the same ligand. It is the metal, rather than the ligand, that appears to have the most profound effect on the catalytic activity in butadiene polymerisation, unlike in the polymerisation of ethylene, where bis(imino)pyridine ligands provide highly active catalysts for a range of 1st row transition metals. 相似文献
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采用溶胶-凝胶法,将苯乙烯-丙烯酸共聚物(PSA)包覆于955 Davison硅胶上得到无机/有机复合微球载体,并在2,6-二[1-(2-异丙基苯基亚胺基)乙基]吡啶/Fe(acac)3均相催化剂中浸渍后得到负载型双亚胺基吡啶铁催化剂.该催化剂在生产高结晶度(72%)聚乙烯的同时,还能生产一定量的α-烯烃.考察了不同膜材料以及聚合条件(不同助催化剂,压力,温度,Al/Fe摩尔比)对聚合活性以及聚合产物性能的影响,发现温度对聚合产物的α-烯烃与聚乙烯的质量比影响最大,助催化剂类型既影响催化剂的活性,也对最终产物的性质有着很大的影响.氯化镁处理的PSA作为膜材料时,负载2,6-二[1-(2-异丙基苯基亚胺基)乙基]吡啶/Fe(acac)3所得到聚乙烯分子量较低(Mw=11.9×104),结晶度较大(72%),熔融指数MI较高(2.35 g/10min),可作为双峰聚乙烯中的低分子量部分加以利用. 相似文献
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A series of 2,6-bis(imino)pyridyl iron(II) and cobalt(II) complexes [2,6-(ArNCMe)2C5H3N]MCl2 (Ar = 2,6-i-Pr2C6H3, M = Fe: 3a, M = Co: 4a; Ar = 2,4,6-i-Pr3C6H2, M = Fe: 3b, M = Co: 4b; Ar = 2,6-i-Pr2-4-BrC6H2, M = Fe: 3c, M = Co: 4c; Ar = 2,4-i-Pr2-6-BrC6H2, M = Fe: 3d, M = Co: 4d) has been synthesized, characterized, and investigated as precatalysts for the polymerization of ethylene in the presence of modified methylaluminoxane (MMAO). The substituents of pyridinebisimine ligands and their positions located significantly influence catalyst activity and polymer property. It is found that the catalytic activities of the iron complexes/MMAO systems are mainly dominated by electronical effect, while those of the cobalt complexes/MMAO systems are primarily controlled by hindering effect. 相似文献
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A surface science model for a silica supported bis(imino)pyridyl iron complexes is applied to reveal the surface chemistry of these heterogeneous polymerization catalysts. The polymerization activity of these models and the molecular weight distribution of the resulting polymer are comparable to similar catalysts supported on amorphous silica. The catalyst deactivates partially during the first hour of ethylene polymerization. Based on photoelectron spectroscopy (XPS) we attribute this deactivation to iron extrusion by the aluminium alkyl activator. 相似文献