Huang Chuanbing, Du Shizhen, Solan Gregory A, Sun Yang, 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.
Dalton Trans. 2017 May 30;46(21):6948-6957. doi: 10.1039/c7dt01077j.
Five examples of α,α'-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridyl-chromium(iii) chlorides (aryl = 2,6-MePh Cr1, 2,6-EtPh Cr2, 2,6-i-PrPh Cr3, 2,4,6-MePh Cr4, 2,6-Et-4-MePh Cr5) have been synthesized by the one-pot template reaction of α,α'-dioxo-2,3:5,6-bis(pentamethylene)pyridine, CrCl·6HO and the corresponding aniline. The molecular structures of Cr1 and Cr4 reveal distorted octahedral geometries with the N,N,N-ligand adopting a mer-configuration. On activation with an aluminium alkyl co-catalyst, Cr1-Cr5 exhibited high catalytic activities in ethylene polymerization and showed outstanding thermal stability operating effectively at 80 °C with activities up to 1.49 × 10 g of PE (mol of Cr) h. Significantly, the nature of the co-catalyst employed had a dramatic effect on the molecular weight of the polymeric material obtained. For example, using diethylaluminium chloride (EtAlCl) in combination with Cr4 gave high density/high molecular weight polyethylene with broad molecular weight distributions (30.9-39.3). By contrast, using modified methylaluminoxane (MMAO), strictly linear polyethylene waxes of lower molecular weight and narrow molecular weight distribution (1.6-2.0) were obtained with vinyl end-groups.
通过α,α'-二氧代-2,3:5,6-双（亚甲基）吡啶、CrCl₃·6H₂O与相应苯胺的一锅法模板反应，合成了五个α,α'-双（芳基亚氨基）-2,3:5,6-双（亚甲基）吡啶基氯化铬（III）（芳基 = 2,6-二甲基苯基Cr1、2,6-二乙基苯基Cr2、2,6-二异丙基苯基Cr3、2,4,6-三甲基苯基Cr4、2,6-二乙基-4-甲基苯基Cr5）的实例。Cr1和Cr4的分子结构显示出扭曲的八面体几何构型，N,N,N-配体呈反式构型。用烷基铝助催化剂活化后，Cr1 - Cr5在乙烯聚合中表现出高催化活性，在80℃下能有效运行，热稳定性优异，活性高达1.49×10⁶g PE/（mol Cr·h）。值得注意的是，所用助催化剂的性质对所得聚合材料的分子量有显著影响。例如，将二乙基氯化铝（Et₂AlCl）与Cr4组合使用，可得到具有宽分子量分布（30.9 - 39.3）的高密度/高分子量聚乙烯。相比之下，使用改性甲基铝氧烷（MMAO），可得到具有乙烯基端基、分子量较低且分子量分布窄（1.6 - 2.0）的严格线性聚乙烯蜡。
