Zhu Dongzhi, Jia Dedong, Zhang Qiuyue, Ma Yanping, Mahmood Qaiser, Sun Wen-Hua
Guangxi Key Laboratory of Advanced Structural Materials and Carbon Neutralization, School of Materials and Environment, Guangxi Minzu University, Nanning 530105, China.
Key Laboratory of Engineering Plastics, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China.
Molecules. 2025 Apr 20;30(8):1847. doi: 10.3390/molecules30081847.
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 -2,6-dibenzhydryl groups as sterically demanding motifs and -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 and ), revealing deviations from ideal tetrahedral geometry. Upon activation with EtAlCl, these complexes demonstrated exceptional ethylene polymerization activity, achieving a remarkable value of 13.67 × 10 g PE mol (Ni) h at 20 °C. Notably, even at 80 °C, the nickel complexes maintained a high activity of 1.97 × 10 g PE mol (Ni) h, showcasing superiority compared to previously reported unsymmetrical 2,3-bis(arylimino)butane-nickel complexes. The resulting polyethylenes exhibited ultra-high molecular weights (: 3.33-19.47 × 10 g mol) and tunable branching densities (84-217/1000C), which were effectively controlled by polymerization temperature. Moreover, the mechanical properties of the polyethylenes, including tensile strength ( = 0.74-16.83 MPa), elongation at break ( = 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.
α-二亚胺镍配合物的催化性能对其配体骨架的结构修饰高度敏感。在本研究中，提出并合成了一系列不对称的2,3-双（芳基亚氨基）丁烷-镍配合物，其具有作为空间位阻基团的-2,6-二苄基和作为给电子增强剂的-甲基。使用傅里叶变换红外光谱（FTIR）、元素分析和单晶X射线衍射（用于 和 ）对这些镍配合物进行了全面表征，结果表明其偏离了理想的四面体几何结构。在用EtAlCl活化后，这些配合物表现出优异的乙烯聚合活性，在20℃下达到了13.67×10 g PE mol（Ni）h的显著值。值得注意的是，即使在80℃下，镍配合物仍保持1.97×10 g PE mol（Ni）h的高活性，与先前报道的不对称2,3-双（芳基亚氨基）丁烷-镍配合物相比具有优势。所得聚乙烯呈现出超高分子量（：3.33 - 19.47×10 g mol）和可调节的支化密度（84 - 217/1000C），这可通过聚合温度有效控制。此外，通过优化分子量、结晶度和支化度，可精细调整聚乙烯的力学性能，包括拉伸强度（ = 0.74 - 16.83 MPa）、断裂伸长率（ = 271 - 475%）和弹性回复率（SR = 42 - 74%）。制备的聚乙烯表现出出色的弹性回复率，这是高性能热塑性弹性体的一个标志，使其成为先进材料应用的有前途的候选者。
