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A π–π interaction strategy for targeting highly thermostable bis(arylimino)pyridyliron precatalysts in ethylene polymerization.

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Title: A π–π interaction strategy for targeting highly thermostable bis(arylimino)pyridyliron precatalysts in ethylene polymerization.
Authors: Zada, Muhammad1,2 (AUTHOR), Zhang, Qiuyue2 (AUTHOR), Mahmood, Qaiser3 (AUTHOR) qaiser@ccelab.com.cn, Ma, Yanping2 (AUTHOR), Sun, Yang2 (AUTHOR) whsun@iccas.ac.cn, Sun, Wen-Hua2,3 (AUTHOR)
Source: Dalton Transactions: An International Journal of Inorganic Chemistry. 5/21/2025, Vol. 54 Issue 19, p7676-7689. 14p.
Subjects: Thermal stability, Catalytic activity, Catalysts, Ethylene synthesis, Intermolecular forces, Iron catalysts, Molecular weights
Abstract: The suboptimal catalytic performance of bis(arylimino)pyridyliron precatalysts in ethylene polymerization at elevated temperatures remains a significant challenge. In this study, a series of six bis(arylimino)pyridyliron chloride precatalysts with the incorporation of the benzosuberyl steric bulk were prepared and investigated for ethylene polymerization. Capping the axial sites of the iron center with the benzosuberyl steric bulk resulted in π–π interactions between the phenyl group and the chelate backbone, with a distance of ca. 3.293 Å for Fe3iPr, shorter than the sum of the van der Waals radii of carbon atoms (3.4 Å), as confirmed by single-crystal X-ray diffraction. These non-covalent interactions enhanced the thermal stability, catalytic activity, and polymer molecular weights. On activation with MAO or MMAO cocatalysts, these precatalysts exhibited the maximum activity of 2.53 × 107 gPE mol−1Fe h−1 at 80 °C and 1.88 × 107 gPE mol−1Fe h−1 at 100 °C, demonstrating their unprecedented thermal stability. The molecular weight of the produced polyethylene remained high, even at elevated temperatures. Moreover, ligand modifications had a pronounced impact on polymerization outcomes: the least sterically hindered complex, while producing comparatively lower molecular weight polyethylene, displayed higher activity and the most sterically hindered one showed the opposite tendency. The molecular weight dispersity of polyethylene showed a strong correlation with the precatalyst structure and reaction conditions. High melting points confirmed the presence of strictly linear structures with high vinyl end groups (up to 74%), as verified using 1H/13C NMR spectra. A comparison of structurally related iron precatalysts revealed significant improvements in both thermal stability and catalytic activity, attributed to the π–π interactions present in the current iron precatalysts. [ABSTRACT FROM AUTHOR]
Copyright of Dalton Transactions: An International Journal of Inorganic Chemistry is the property of Royal Society of Chemistry and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: A π–π interaction strategy for targeting highly thermostable bis(arylimino)pyridyliron precatalysts in ethylene polymerization.
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  Data: <searchLink fieldCode="AR" term="%22Zada%2C+Muhammad%22">Zada, Muhammad</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Zhang%2C+Qiuyue%22">Zhang, Qiuyue</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Mahmood%2C+Qaiser%22">Mahmood, Qaiser</searchLink><relatesTo>3</relatesTo> (AUTHOR)<i> qaiser@ccelab.com.cn</i><br /><searchLink fieldCode="AR" term="%22Ma%2C+Yanping%22">Ma, Yanping</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Sun%2C+Yang%22">Sun, Yang</searchLink><relatesTo>2</relatesTo> (AUTHOR)<i> whsun@iccas.ac.cn</i><br /><searchLink fieldCode="AR" term="%22Sun%2C+Wen-Hua%22">Sun, Wen-Hua</searchLink><relatesTo>2,3</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Dalton+Transactions%3A+An+International+Journal+of+Inorganic+Chemistry%22">Dalton Transactions: An International Journal of Inorganic Chemistry</searchLink>. 5/21/2025, Vol. 54 Issue 19, p7676-7689. 14p.
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  Data: <searchLink fieldCode="DE" term="%22Thermal+stability%22">Thermal stability</searchLink><br /><searchLink fieldCode="DE" term="%22Catalytic+activity%22">Catalytic activity</searchLink><br /><searchLink fieldCode="DE" term="%22Catalysts%22">Catalysts</searchLink><br /><searchLink fieldCode="DE" term="%22Ethylene+synthesis%22">Ethylene synthesis</searchLink><br /><searchLink fieldCode="DE" term="%22Intermolecular+forces%22">Intermolecular forces</searchLink><br /><searchLink fieldCode="DE" term="%22Iron+catalysts%22">Iron catalysts</searchLink><br /><searchLink fieldCode="DE" term="%22Molecular+weights%22">Molecular weights</searchLink>
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  Data: The suboptimal catalytic performance of bis(arylimino)pyridyliron precatalysts in ethylene polymerization at elevated temperatures remains a significant challenge. In this study, a series of six bis(arylimino)pyridyliron chloride precatalysts with the incorporation of the benzosuberyl steric bulk were prepared and investigated for ethylene polymerization. Capping the axial sites of the iron center with the benzosuberyl steric bulk resulted in π–π interactions between the phenyl group and the chelate backbone, with a distance of ca. 3.293 Å for Fe3iPr, shorter than the sum of the van der Waals radii of carbon atoms (3.4 Å), as confirmed by single-crystal X-ray diffraction. These non-covalent interactions enhanced the thermal stability, catalytic activity, and polymer molecular weights. On activation with MAO or MMAO cocatalysts, these precatalysts exhibited the maximum activity of 2.53 × 107 gPE mol−1Fe h−1 at 80 °C and 1.88 × 107 gPE mol−1Fe h−1 at 100 °C, demonstrating their unprecedented thermal stability. The molecular weight of the produced polyethylene remained high, even at elevated temperatures. Moreover, ligand modifications had a pronounced impact on polymerization outcomes: the least sterically hindered complex, while producing comparatively lower molecular weight polyethylene, displayed higher activity and the most sterically hindered one showed the opposite tendency. The molecular weight dispersity of polyethylene showed a strong correlation with the precatalyst structure and reaction conditions. High melting points confirmed the presence of strictly linear structures with high vinyl end groups (up to 74%), as verified using 1H/13C NMR spectra. A comparison of structurally related iron precatalysts revealed significant improvements in both thermal stability and catalytic activity, attributed to the π–π interactions present in the current iron precatalysts. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Dalton Transactions: An International Journal of Inorganic Chemistry is the property of Royal Society of Chemistry and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1039/d5dt00571j
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      – Code: eng
        Text: English
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        PageCount: 14
        StartPage: 7676
    Subjects:
      – SubjectFull: Thermal stability
        Type: general
      – SubjectFull: Catalytic activity
        Type: general
      – SubjectFull: Catalysts
        Type: general
      – SubjectFull: Ethylene synthesis
        Type: general
      – SubjectFull: Intermolecular forces
        Type: general
      – SubjectFull: Iron catalysts
        Type: general
      – SubjectFull: Molecular weights
        Type: general
    Titles:
      – TitleFull: A π–π interaction strategy for targeting highly thermostable bis(arylimino)pyridyliron precatalysts in ethylene polymerization.
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            NameFull: Zada, Muhammad
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            NameFull: Zhang, Qiuyue
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            NameFull: Ma, Yanping
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            NameFull: Sun, Yang
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            – D: 21
              M: 05
              Text: 5/21/2025
              Type: published
              Y: 2025
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              Value: 54
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              Value: 19
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