Tuning 2,3-Bis(arylimino)butane-nickel Precatalysts for High-Molecular-Weight Polyethylene Elastomers
The catalytic performance of α-diiminonickel complexes is highly sensitive to structural modifications in their ligand frameworks. In this study, a series of unsymmetrical 2,3-bis(arylimino)butane-nickel complexes featuring <i>ortho</i>-2,6-dibenzhydryl groups as sterically demanding mot...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-04-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/8/1847 |
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| Summary: | The catalytic performance of α-diiminonickel complexes is highly sensitive to structural modifications in their ligand frameworks. In this study, a series of unsymmetrical 2,3-bis(arylimino)butane-nickel complexes featuring <i>ortho</i>-2,6-dibenzhydryl groups as sterically demanding motifs and <i>para</i>-methyl groups as electron-donating enhancers were proposed and synthesized. These nickel complexes were thoroughly characterized using FTIR, elemental analysis, and single-crystal X-ray diffraction (for <b>Ni4</b> and <b>Ni5</b>), revealing deviations from ideal tetrahedral geometry. Upon activation with Et<sub>2</sub>AlCl, these complexes demonstrated exceptional ethylene polymerization activity, achieving a remarkable value of 13.67 × 10<sup>6</sup> g PE mol<sup>−1</sup> (Ni) h<sup>−1</sup> at 20 °C. Notably, even at 80 °C, the nickel complexes maintained a high activity of 1.97 × 10<sup>6</sup> g PE mol<sup>−1</sup> (Ni) h<sup>−1</sup>, showcasing superiority compared to previously reported unsymmetrical 2,3-bis(arylimino)butane-nickel complexes. The resulting polyethylenes exhibited ultra-high molecular weights (<i>M</i><sub>w</sub>: 3.33–19.47 × 10<sup>5</sup> g mol<sup>−1</sup>) and tunable branching densities (84–217/1000C), which were effectively controlled by polymerization temperature. Moreover, the mechanical properties of the polyethylenes, including tensile strength (<i>σ</i><sub>b</sub> = 0.74–16.83 MPa), elongation at break (<i>ε</i><sub>b</sub> = 271–475%), and elastic recovery (SR = 42–74%), were finely tailored by optimizing molecular weight, crystallinity, and branching degree. The prepared polyethylenes displayed outstanding elastic recovery, a hallmark of high-performance thermoplastic elastomers, making them promising candidates for advanced material applications. |
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| ISSN: | 1420-3049 |