A novel nickel（II）-complex Ni[L]Cl2-CH3CN（1） containing the tridentate ligand 2,6-bis[1-（2,4,6- trimethylphenylimino）ethyl]pyridine（L） has been synthesized. The crystal structure of complex 1 was determined by...A novel nickel（II）-complex Ni[L]Cl2-CH3CN（1） containing the tridentate ligand 2,6-bis[1-（2,4,6- trimethylphenylimino）ethyl]pyridine（L） has been synthesized. The crystal structure of complex 1 was determined by single crystal X-ray diffraction analysis. The catalytic activity of complex 1 for the polymerization of ethylene was studied under activation with methylaluminoxane（MAO）.展开更多
An unsymmetric 2,6-bis(imino)pyridine iron(II) complex 1' was synthesized. The relationship between catalyststructure and its activity in ethylene polymerization is discussed. The kinetic behavior of ethylene poly...An unsymmetric 2,6-bis(imino)pyridine iron(II) complex 1' was synthesized. The relationship between catalyststructure and its activity in ethylene polymerization is discussed. The kinetic behavior of ethylene polymerization and theeffects of polymerization conditions such as temperature, aluminum/iron molar ratio on the activity of catalyst and thecharacteristics of polyethylene were reported. The unsymmetric catalyst 1' has a good catalytic performance of 3.47×10~6 gPE·mol^(-1)·Fe·h^(-1) at 40℃ with aluminum/iron molar ratio = 2500. A dependence of catalyst activity on themethylaluminoxane (MAO) concentration and reaction temperature was found. The molecular weight (MW) of polyethylenewith broad dispersity is about 10~4-10~5 g/mol. The melting temperature and branching of polyethylenes vary with changingreaction temperature and aluminum/iron molar ratio.展开更多
A comparative thermal decomposition kinetic investigation on Fe(III) complexes of a antipyrine Schiff base ligand, 1,2-Bis(imino-4’-antipyrinyl)ethane (GA)), with varying counter anions viz. CIO4-, NO3-, SCN-, Cl-, a...A comparative thermal decomposition kinetic investigation on Fe(III) complexes of a antipyrine Schiff base ligand, 1,2-Bis(imino-4’-antipyrinyl)ethane (GA)), with varying counter anions viz. CIO4-, NO3-, SCN-, Cl-, and Br-, has been done by thermogravimetric analysis by using Coats-Redfern equation. The kinetic parameters like activation energy (E), pre-exponential factor (A) and entropy of activation (ΔS) were quantified. On comparing the various kinetic parameters, lower activation energy was observed in second stage as compared to first thermal decomposition stage. The same trend has been observed for pre-exponential factor (A) and entropy of activation (ΔS). The present results show that the starting materials having higher activation energy (E), are more stable than the intermediate products, however;the intermediate products possess well-ordered chemical structure due to their highly negative entropy of activation (ΔS) values. The present investigation proves that the counter anions play an important role on the thermal decomposition kinetics of the complexes.展开更多
Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization.In the present study,a...Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization.In the present study,a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions.By incorporation of strong electron-withdrawing groups(F and NO_(2))and a steric component(benzhydryl)into the parent bis(imino)pyridine ligand,the catalytic performance of these precatalysts was optimized.On activation with MAO or MMAO,these precatalysts with relatively open structure achieved unprecedented ethylene polymerization rates at 60℃(up to 27.6×10^(6)g mol^(−1)h^(−1))and remained effective at temperatures up to 100℃.Chain growth reactions were moderate,resulting in polyethylene with molecular weights up to 61.0 kg/mol and broad bimodal dispersity index.High crystallinity and melt temperature indicated a strictly linear microstructure,as further confirmed by high-temperature^(1)H/^(13)C NMR measurements.Of significant note that chain termination predominantly occurred throughβ-elimination(up to 84.5%),yielding vinyl-terminated long-chain olefins.These functionalα-macro-olefins are valuable as precursors for postfunctionalization,expanding the potential applications of polyethylene across various sectors.展开更多
The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. Th...The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.展开更多
(1,4-Bis-（4-bromobenzoyl）benzene) as the monomer has been synthesized and characterized by Friedel-Crafts benzoylation reaction.Novel poly（imino ketone）s（PIKs） as high performance polymers have been obtained by ...(1,4-Bis-（4-bromobenzoyl）benzene) as the monomer has been synthesized and characterized by Friedel-Crafts benzoylation reaction.Novel poly（imino ketone）s（PIKs） as high performance polymers have been obtained by the condensation polymerization of（1,4-bis-（4-bromobenzoyl）benzene） and aromatic diamines via palladium-catalyzed aryl amination reaction.The strcture of PIKs is characterized by means of FT-IR and（）1H-NMR spectroscopy,and the results show an agreement with the proposed structure.DSC and TG measurements show that PIKs possess high glass transition temperature（Tg>230℃） and good thermal stability with high decomposition temperatures（TD>500℃）.PIKs also exhibit the excellent solubility,PIK-3 can be dissolved in common organic solvent CHCl3 at room temperature（20℃）.展开更多
基金National Natural Science Foundation of China(Nos.20771030 and 20671025)Development Program for Outstanding Young Teachers in Harbin Institute of Technology(No.HITQNJS.2006.029)+1 种基金Science Innovation Special Founda-tion of Harbin City in China(No.2006RFQXG037)Young Foundation of Heilongjiang Province, China(No.QC06C029)
文摘A novel nickel（II）-complex Ni[L]Cl2-CH3CN（1） containing the tridentate ligand 2,6-bis[1-（2,4,6- trimethylphenylimino）ethyl]pyridine（L） has been synthesized. The crystal structure of complex 1 was determined by single crystal X-ray diffraction analysis. The catalytic activity of complex 1 for the polymerization of ethylene was studied under activation with methylaluminoxane（MAO）.
基金the National Natural Science Foundation of China(No.2 0 374 0 2 3) and the Foundation of the Ministry ofScience and Technology of China(No.2 0 0 2 CB6 1340 0 3
基金This work was financially supported by the National Natural Science Foundation of China (No. 29734141, 50103012) Core Research for Engineering Innovation KGCX2-203, the Foundation of "One Hundred Talents" program for W-H Sun, Chinese Academy of Sciences
文摘An unsymmetric 2,6-bis(imino)pyridine iron(II) complex 1' was synthesized. The relationship between catalyststructure and its activity in ethylene polymerization is discussed. The kinetic behavior of ethylene polymerization and theeffects of polymerization conditions such as temperature, aluminum/iron molar ratio on the activity of catalyst and thecharacteristics of polyethylene were reported. The unsymmetric catalyst 1' has a good catalytic performance of 3.47×10~6 gPE·mol^(-1)·Fe·h^(-1) at 40℃ with aluminum/iron molar ratio = 2500. A dependence of catalyst activity on themethylaluminoxane (MAO) concentration and reaction temperature was found. The molecular weight (MW) of polyethylenewith broad dispersity is about 10~4-10~5 g/mol. The melting temperature and branching of polyethylenes vary with changingreaction temperature and aluminum/iron molar ratio.
文摘A comparative thermal decomposition kinetic investigation on Fe(III) complexes of a antipyrine Schiff base ligand, 1,2-Bis(imino-4’-antipyrinyl)ethane (GA)), with varying counter anions viz. CIO4-, NO3-, SCN-, Cl-, and Br-, has been done by thermogravimetric analysis by using Coats-Redfern equation. The kinetic parameters like activation energy (E), pre-exponential factor (A) and entropy of activation (ΔS) were quantified. On comparing the various kinetic parameters, lower activation energy was observed in second stage as compared to first thermal decomposition stage. The same trend has been observed for pre-exponential factor (A) and entropy of activation (ΔS). The present results show that the starting materials having higher activation energy (E), are more stable than the intermediate products, however;the intermediate products possess well-ordered chemical structure due to their highly negative entropy of activation (ΔS) values. The present investigation proves that the counter anions play an important role on the thermal decomposition kinetics of the complexes.
基金financially supported by the Chemistry and Chemical Engineering Guangdong Laboratory(2111018 and 2132012)K.F.T.would like to express gratitude towards the ANSO Scholarship Program for their support.
文摘Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization.In the present study,a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions.By incorporation of strong electron-withdrawing groups(F and NO_(2))and a steric component(benzhydryl)into the parent bis(imino)pyridine ligand,the catalytic performance of these precatalysts was optimized.On activation with MAO or MMAO,these precatalysts with relatively open structure achieved unprecedented ethylene polymerization rates at 60℃(up to 27.6×10^(6)g mol^(−1)h^(−1))and remained effective at temperatures up to 100℃.Chain growth reactions were moderate,resulting in polyethylene with molecular weights up to 61.0 kg/mol and broad bimodal dispersity index.High crystallinity and melt temperature indicated a strictly linear microstructure,as further confirmed by high-temperature^(1)H/^(13)C NMR measurements.Of significant note that chain termination predominantly occurred throughβ-elimination(up to 84.5%),yielding vinyl-terminated long-chain olefins.These functionalα-macro-olefins are valuable as precursors for postfunctionalization,expanding the potential applications of polyethylene across various sectors.
基金carried out according to the program of Fundamental Scientific Research of the Russian Federation
文摘The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.
文摘(1,4-Bis-（4-bromobenzoyl）benzene) as the monomer has been synthesized and characterized by Friedel-Crafts benzoylation reaction.Novel poly（imino ketone）s（PIKs） as high performance polymers have been obtained by the condensation polymerization of（1,4-bis-（4-bromobenzoyl）benzene） and aromatic diamines via palladium-catalyzed aryl amination reaction.The strcture of PIKs is characterized by means of FT-IR and（）1H-NMR spectroscopy,and the results show an agreement with the proposed structure.DSC and TG measurements show that PIKs possess high glass transition temperature（Tg>230℃） and good thermal stability with high decomposition temperatures（TD>500℃）.PIKs also exhibit the excellent solubility,PIK-3 can be dissolved in common organic solvent CHCl3 at room temperature（20℃）.
