Hosseinzadeh Zahra, Zhang Qiuyue, Gao Jiahao, Wang Yizhou, Wang Quanchao, Ren Geng, Liang Tongling, Ma Yanping, Sun Wen-Hua
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China.
CAS Research/Education Center for Excellence in Molecular Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Dalton Trans. 2025 Aug 19;54(33):12590-12600. doi: 10.1039/d5dt00837a.
The bis(imino)pyridylferrous chloride complexes bearing -trifluoromethoxy and -difluorobenzhydryl substituents, namely, 2-(1-{2,6-bis[bis(4-fluorophenyl)methyl]-4-trifluoromethoxyphenyl-imino}ethyl)-6-[1-(2,6-di(R)-4-R-phenylimino) ethyl]pyridyl iron(II) chloride (where R = Me, R = H, Fe1; R = Et, R = H, Fe2; R = i-Pr, R = H, Fe3; R = Me, R = Me, Fe4; R = Et, R = Me, Fe5; and R = (4-FCH)CH, R = OCF, Fe6) were successfully synthesized and thoroughly characterized. The X-ray crystal structures of Fe4 and Fe6 were also determined. The catalytic performance of all the new iron complexes was systematically evaluated for ethylene polymerization, with a detailed comparative analysis conducted against previously published studies. Notably, iron complexes Fe1-Fe5 demonstrated exceptional catalytic activity and thermal stability upon activation with MAO, while Fe6 showed inferior performance due to its significant steric hindrance. Among them, Fe1 demonstrated the highest activity, achieving a peak of 17.28 × 10 g (PE) mol (Fe) h at 70 °C in -hexane, which markedly surpassed the activity levels of other structurally related iron complexes, indicating the beneficial impact of incorporating multi-fluoro groups. Remarkably, the current iron pre-catalysts generally revealed superior performance in hexane compared to toluene, even when using a reduced quantity of co-catalyst, thereby underscoring the pivotal role of solvent polarity in governing the polymerization process. Furthermore, the analysis of the generated polyethylenes (PEs) revealed a high degree of linearity in the polymers, featuring vinyl end groups and exhibiting a broad spectrum of molecular weights (: 4.5-567.9 kg mol).
带有 - 三氟甲氧基和 - 二氟二苯甲基取代基的双（亚氨基）吡啶基氯化亚铁配合物，即2-(1-{2,6-双[双(4-氟苯基)甲基]-4-三氟甲氧基苯基 - 亚氨基}乙基)-6-[1-(2,6-二(R)-4-R-苯基亚氨基)乙基]吡啶基氯化铁(II)（其中R = 甲基，R' = 氢，Fe1；R = 乙基，R' = 氢，Fe2；R = 异丙基，R' = 氢，Fe3；R = 甲基，R' = 甲基，Fe4；R = 乙基，R' = 甲基，Fe5；以及R = (4-氟苄基)甲基，R' = 三氟甲氧基，Fe6）已成功合成并得到全面表征。还测定了Fe4和Fe6的X射线晶体结构。对所有新型铁配合物在乙烯聚合反应中的催化性能进行了系统评估，并与先前发表的研究进行了详细对比分析。值得注意的是，铁配合物Fe1 - Fe5在用甲基铝氧烷（MAO）活化后表现出卓越的催化活性和热稳定性，而Fe6由于其显著的空间位阻表现较差。其中，Fe1表现出最高活性，在70℃的正己烷中达到17.28×10⁶ g（聚乙烯）mol⁻¹（铁）⁻¹ h⁻¹的峰值，明显超过其他结构相关铁配合物的活性水平，表明引入多氟基团的有益影响。值得注意的是，当前的铁预催化剂在正己烷中通常比在甲苯中表现出更优异的性能，即使使用减少量的助催化剂，从而突出了溶剂极性在控制聚合过程中的关键作用。此外，对生成的聚乙烯（PEs）的分析表明聚合物具有高度线性，具有乙烯基端基且分子量分布范围广（：4.5 - 567.9 kg mol⁻¹）。
