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Wenhua Sun - One of the best experts on this subject based on the ideXlab platform.

Carl Redshaw - One of the best experts on this subject based on the ideXlab platform.

  • synthesis characterization and ethylene polymerization behavior of binuclear iron complexes bearing n n bis 1 6 1 arylimino ethyl pyridin 2 yl ethylidene benzidines
    RSC Advances, 2013
    Co-Authors: Qifeng Xing, Carl Redshaw, Tong Zhao, Yusen Qiao, Lin Wang, Wenhua Sun
    Abstract:

    A series of N,N′-bis(1-(6-(1-(arylimino)ethyl)pyridin-2-yl)ethylidene)benzidines and the bi-metallic iron complexes thereof have been synthesized and fully characterized. All iron complexes, when activated by MAO or MMAO, exhibited high activities of up to 1.3 × 107 g mol−1 (Fe) h−1 for the polymerization of ethylene. On comparison with their mononuclear counterparts, such bi-metallic complexes not only retain a relatively high activity at elevated temperatures (up to 70 °C), but also exhibit increased lifetimes. The polyethylenes obtained were characterized by GPC, DSC and high temperature NMR spectroscopy, which indicated multimodal and highly linear features.

  • synthesis characterization and catalytic behavior toward ethylene of 2 1 4 6 dimethyl 2 benzhydrylphenylimino ethyl 6 1 arylimino ethyl pyridylmetal iron or cobalt chlorides
    Dalton Transactions, 2013
    Co-Authors: Shaoli Wang, Tongling Liang, Carl Redshaw, Wenhua Sun
    Abstract:

    A series of 2-[1-(4,6-dimethyl-2-benzhydrylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridines was synthesized and used to prepare the iron(II) and cobalt(II) chloride complexes thereof. All organic compounds were fully characterized by elemental analysis, IR and NMR (1H/13C) spectroscopy, whilst the metal complexes were characterized by elemental analysis and IR spectroscopy as well as by single-crystal X-ray diffraction studies (for two representative cobalt complexes), which revealed that the geometry at the metal was either pseudo-square-pyramidal or trigonal bipyramidal. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all metal complex pre-catalysts exhibited high activities for ethylene polymerization. The iron pre-catalysts show much higher activity than did their cobalt analogues; however, the iron catalytic systems generally produced polyethylene of wide molecular weight polydispersity. At elevated reaction temperature, the polyethylene was of lower molecular weight, but revealed narrow polydispersity.

  • enhancing the activity and thermal stability of iron precatalysts using 2 1 2 6 bis bis 4 fluorophenyl methyl 4 methylphenylimino ethyl 6 1 arylimino ethyl pyridines
    Macromolecular Chemistry and Physics, 2012
    Co-Authors: Wenjuan Zhang, Wenhua Sun, Xiang Hao, Weizhen Zhao, Carl Redshaw
    Abstract:

    A series of 2-(1-{2,6-bis[bis(4-fluorophenyl)methyl]-4-methylphenylimino}ethyl)-6- [1-(arylimino)ethyl]pyridine ligands is synthesized and fully characterized. The corresponding iron complexes are prepared and characterized by single-crystal X-ray diffraction for representative iron complexes, among other methods, revealing a pseudo square-pyramidal geometry at the iron center. Upon activation with MMAO, all iron precatalysts exhibit high activity in ethylene polymerization, producing linear polyethylene. The observed activity is the highest reported for iron-based precatalysts of this type. The polymerization parameters are shown to strongly affect the catalytic behavior, and both the activity and the polymer properties (i.e. or /) can be controlled.

  • 2 1 2 6 dibenzhydryl 4 chlorophenylimino ethyl 6 1 arylimino ethyl pyridyliron ii dichlorides synthesis characterization and ethylene polymerization behavior
    Polymer, 2012
    Co-Authors: Xiaoping Cao, Wenhua Sun, Carl Redshaw, Xiang Hao, Weizhen Zhao, Zhengguo Cai, Takeshi Shiono
    Abstract:

    A series of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine ligands (L1–L5) as well as the ligand 2,6-bis[1-(2,6-dibenzhydryl-4-chloro-phenylimino)ethyl]pyridine (L6) were synthesized and reacted with FeCl2·4H2O to afford the iron(II) dichloride complexes [LFeCl2] (Fe1–Fe6). All new compounds were fully characterized by elemental and spectroscopic analysis, and the molecular structures of the complexes Fe1, Fe2 and Fe4 were determined by single-crystal X-ray diffraction, which revealed a pseudo-square-pyramidal geometry at iron. Upon activation with either MAO or MMAO, all iron pre-catalysts exhibited very high activity in ethylene polymerization with good thermal stability. To the best of our knowledge, the current system showed the highest activity amongst iron bis(imino)pyridine pre-catalysts reported to-date. The polymerization parameters were explored to determine the optimum conditions for catalytic activity, which were typically found to be 2500 eq. Al to Fe at 60 °C in the presence of MMAO, and 80 °C in the presence of MAO. The resultant polyethylene possessed a narrow molecular polydispersity index (PDI) consistent with the formation of single-site active species.

  • 2 1 2 6 dibenzhydryl 4 methylphenylimino ethyl 6 1 arylimino ethyl pyridylnickel ii halides synthesis characterization and ethylene oligomerization behavior
    Journal of Organometallic Chemistry, 2012
    Co-Authors: Xiaohua Hou, Jingjuan Lai, Yongwen Liu, Carl Redshaw, Wenhua Sun
    Abstract:

    Abstract A series of nickel(II) halide complexes ligated by 2-[1-(2,6-dibenzhydryl-4-methyl-phenylimino)ethyl]-6-[1-(arylimino)-ethyl]pyridines was synthesized and characterized by FT–IR spectroscopy and elemental analysis. Single-crystal X-ray crystallographic studies revealed that the nickel halide complexes possess pseudo square-pyramidal geometry at nickel. Following screening with the co-catalysts Et2AlCl, MAO, MMAO and ethylaluminum sesquichloride (EASC, Et3Al2Cl3), EASC was chosen as the co-catalyst of choice, and activities as high as 2.5 × 106 g mol−1 (Ni) h−1 were observed for ethylene oligomerization. The influence of the ligands and of the reaction parameters on the catalytic behavior of the nickel pre-catalysts was investigated.

Weizhen Zhao - One of the best experts on this subject based on the ideXlab platform.

  • high cis 1 4 polyisoprene or cis 1 4 3 4 binary polyisoprene synthesized using 2 benzimidazolyl 6 1 arylimino ethyl pyridine cobalt ii dichlorides
    Polymer International, 2013
    Co-Authors: Geng Wang, Weizhen Zhao, Xiubo Jiang, Wei Yao, Wenhua Sun
    Abstract:

    Polyisoprene (PI) with a high content of cis-1,4 (up to 95%) or cis-1,4/3,4 binary structures was synthesized using a cobalt system in toluene. The cobalt system, which exhibited high activities (up to 3.50 × 106 g PI (mol Co)−1 h−1), contained a series of 2-(benzimidazolyl)-6-(1-(arylimino)ethyl)pyridine cobalt(II) dichlorides activated with ethylaluminium sesquichloride. The nature of the ligands and the reaction conditions significantly affected both the catalytic performance of the cobalt complexes as well as the structures of the resultant PI. The stereospecific polymerization of isoprene could be tuned via changing either the co-catalyst or solvent: for example, increased content of 3,4 PI (up to 36.6%) was achievable in heptane in the presence of diethylaluminium chloride. Sequence distribution analysis by 13C NMR spectroscopy indicated that most 3,4 units occurred randomly in the PI chains. © 2013 Society of Chemical Industry

  • enhancing the activity and thermal stability of iron precatalysts using 2 1 2 6 bis bis 4 fluorophenyl methyl 4 methylphenylimino ethyl 6 1 arylimino ethyl pyridines
    Macromolecular Chemistry and Physics, 2012
    Co-Authors: Wenjuan Zhang, Wenhua Sun, Xiang Hao, Weizhen Zhao, Carl Redshaw
    Abstract:

    A series of 2-(1-{2,6-bis[bis(4-fluorophenyl)methyl]-4-methylphenylimino}ethyl)-6- [1-(arylimino)ethyl]pyridine ligands is synthesized and fully characterized. The corresponding iron complexes are prepared and characterized by single-crystal X-ray diffraction for representative iron complexes, among other methods, revealing a pseudo square-pyramidal geometry at the iron center. Upon activation with MMAO, all iron precatalysts exhibit high activity in ethylene polymerization, producing linear polyethylene. The observed activity is the highest reported for iron-based precatalysts of this type. The polymerization parameters are shown to strongly affect the catalytic behavior, and both the activity and the polymer properties (i.e. or /) can be controlled.

  • 2 1 2 6 dibenzhydryl 4 chlorophenylimino ethyl 6 1 arylimino ethyl pyridyliron ii dichlorides synthesis characterization and ethylene polymerization behavior
    Polymer, 2012
    Co-Authors: Xiaoping Cao, Wenhua Sun, Carl Redshaw, Xiang Hao, Weizhen Zhao, Zhengguo Cai, Takeshi Shiono
    Abstract:

    A series of 2-[1-(2,6-dibenzhydryl-4-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine ligands (L1–L5) as well as the ligand 2,6-bis[1-(2,6-dibenzhydryl-4-chloro-phenylimino)ethyl]pyridine (L6) were synthesized and reacted with FeCl2·4H2O to afford the iron(II) dichloride complexes [LFeCl2] (Fe1–Fe6). All new compounds were fully characterized by elemental and spectroscopic analysis, and the molecular structures of the complexes Fe1, Fe2 and Fe4 were determined by single-crystal X-ray diffraction, which revealed a pseudo-square-pyramidal geometry at iron. Upon activation with either MAO or MMAO, all iron pre-catalysts exhibited very high activity in ethylene polymerization with good thermal stability. To the best of our knowledge, the current system showed the highest activity amongst iron bis(imino)pyridine pre-catalysts reported to-date. The polymerization parameters were explored to determine the optimum conditions for catalytic activity, which were typically found to be 2500 eq. Al to Fe at 60 °C in the presence of MMAO, and 80 °C in the presence of MAO. The resultant polyethylene possessed a narrow molecular polydispersity index (PDI) consistent with the formation of single-site active species.

  • 2 1 2 4 dibenzhydryl 6 methylphenylimino ethyl 6 1 arylimino ethyl pyridylcobalt ii dichlorides synthesis characterization and ethylene polymerization behavior
    Polymer Chemistry, 2012
    Co-Authors: Jingjuan Lai, Yongwen Liu, Carl Redshaw, Weizhen Zhao, Wenhong Yang, Tongling Liang, Wenhua Sun
    Abstract:

    A series of cobalt(II) dichloride complexes ligated by 2-[1-(2,4-dibenzhydryl-6-methylphenylimino) ethyl]-6-[1-(arylimino)ethyl]pyridines was synthesized and characterized by FT-IR spectroscopy and elemental analysis. The molecular structure of the representative complex Co4 (R1 = Me, R2 = Me) was confirmed as pseudo square-pyramidal geometry at cobalt by single-crystal X-ray diffraction. Upon treatment with the co-catalysts MAO or MMAO, all cobalt pre-catalysts exhibited high activities up to 1.81 × 107 g PE mol−1(Co) h−1 in ethylene polymerization, and produced polyethylene products with molecular weights in the tens of thousands and narrow molecular weight distributions. The influence of the reaction parameters and nature of the ligands on the catalytic behavior of the title cobalt complexes was investigated.

  • controlling the ethylene polymerization parameters in iron pre catalysts of the type 2 1 2 4 dibenzhydryl 6 methylphenylimino ethyl 6 1 arylimino ethyl pyridyliron dichloride
    Polymer, 2012
    Co-Authors: Weizhen Zhao, Carl Redshaw, Hao Liu, Xiang Hao, Wenhong Yang, Shengju Song, Wenhua Sun
    Abstract:

    The ligand series 2-[1-(2,4-dibenzhydryl-6-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridines and the iron(II) chloride complexes thereof have been synthesized and characterized by elemental and spectroscopic analyses. The molecular structures of C1 and C2 , determined by single-crystal X-ray diffraction analysis, confirmed a pseudo-square-pyramidal geometry at the iron center. Upon treatment with either MAO or MMAO, all iron pre-catalysts possessed good thermo-stability and exhibited high activities [up to 5.22 × 10 7  g mol −1 (Fe) h −1 ] toward ethylene polymerization, producing highly linear polyethylene products. Optimization of the reaction parameters gave polyethylenes with narrow molecular weight distributions, indicating that single-site active species were formed; the molecular weights of the resultant polyethylenes could also be controlled.

Xiang Hao - One of the best experts on this subject based on the ideXlab platform.

Jingjuan Lai - One of the best experts on this subject based on the ideXlab platform.

  • 2 1 2 6 dibenzhydryl 4 methylphenylimino ethyl 6 1 arylimino ethyl pyridylnickel ii halides synthesis characterization and ethylene oligomerization behavior
    Journal of Organometallic Chemistry, 2012
    Co-Authors: Xiaohua Hou, Jingjuan Lai, Yongwen Liu, Carl Redshaw, Wenhua Sun
    Abstract:

    Abstract A series of nickel(II) halide complexes ligated by 2-[1-(2,6-dibenzhydryl-4-methyl-phenylimino)ethyl]-6-[1-(arylimino)-ethyl]pyridines was synthesized and characterized by FT–IR spectroscopy and elemental analysis. Single-crystal X-ray crystallographic studies revealed that the nickel halide complexes possess pseudo square-pyramidal geometry at nickel. Following screening with the co-catalysts Et2AlCl, MAO, MMAO and ethylaluminum sesquichloride (EASC, Et3Al2Cl3), EASC was chosen as the co-catalyst of choice, and activities as high as 2.5 × 106 g mol−1 (Ni) h−1 were observed for ethylene oligomerization. The influence of the ligands and of the reaction parameters on the catalytic behavior of the nickel pre-catalysts was investigated.

  • 2 1 2 4 dibenzhydryl 6 methylphenylimino ethyl 6 1 arylimino ethyl pyridylcobalt ii dichlorides synthesis characterization and ethylene polymerization behavior
    Polymer Chemistry, 2012
    Co-Authors: Jingjuan Lai, Yongwen Liu, Carl Redshaw, Weizhen Zhao, Wenhong Yang, Tongling Liang, Wenhua Sun
    Abstract:

    A series of cobalt(II) dichloride complexes ligated by 2-[1-(2,4-dibenzhydryl-6-methylphenylimino) ethyl]-6-[1-(arylimino)ethyl]pyridines was synthesized and characterized by FT-IR spectroscopy and elemental analysis. The molecular structure of the representative complex Co4 (R1 = Me, R2 = Me) was confirmed as pseudo square-pyramidal geometry at cobalt by single-crystal X-ray diffraction. Upon treatment with the co-catalysts MAO or MMAO, all cobalt pre-catalysts exhibited high activities up to 1.81 × 107 g PE mol−1(Co) h−1 in ethylene polymerization, and produced polyethylene products with molecular weights in the tens of thousands and narrow molecular weight distributions. The influence of the reaction parameters and nature of the ligands on the catalytic behavior of the title cobalt complexes was investigated.