Zhang Randi, Huang Yongfeng, Solan Gregory A, Zhang Wenjuan, Hu Xinquan, Hao Xiang, 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.
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China.
Dalton Trans. 2019 Jun 21;48(23):8175-8185. doi: 10.1039/c9dt01345h. Epub 2019 May 15.
Six types of 2,8-bis(imino)-7,7-dimethyl-5,6-dihydroquinoline, 2-(ArN[double bond, length as m-dash]CMe)-8-(ArN)-7,7-MeCHN (Ar = 2,6-MeCHL1, 2,6-EtCHL2, 2,6-PrCHL3, 2,4,6-MeCHL4, 2,6-Et-4-MeCHL5, 2,4,6-BuCHL6), distinguishable by their steric and electronic profile, are described that can readily undergo complexation with cobaltous chloride to form their corresponding LCoCl chelates, Co1-Co6. The molecular structures of Co2 and Co3 reveal square pyramidal geometries with ring puckering a feature of the gem-dimethyl section of their unsymmetrical N,N,N'-ligands. On activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the cobalt complexes exhibited exceptionally high activities for ethylene polymerization with levels reaching up to 1.19 × 10 g PE per mol (Co) per h for mesityl-containing Co4. Significantly, these catalysts exhibited good thermal stability by displaying their optimal performance at temperatures up to 70 °C whilst also maintaining appreciable catalytic lifetimes. With the exception of that obtained using the most sterically hindered Co6 (2,4,6-t-butyl), the polyethylenes are of low molecular weight (M≤16.0 kg mol) and of narrow dispersity (M/M≤3.4). Moreover, end-group analysis of these highly linear polymer waxes reveals evidence for unsaturated as well as various levels of fully saturated materials highlighting the role of both β-H elimination and chain transfer to aluminum as termination pathways.
描述了六种2,8 - 双（亚氨基）- 7,7 - 二甲基 - 5,6 - 二氢喹啉，即2 - (ArN═CMe) - 8 - (ArN) - 7,7 - Me₂CHN（Ar = 2,6 - Me₂CHL1、2,6 - Et₂CHL2、2,6 - Pr₂CHL3、2,4,6 - Me₃CHL4、2,6 - Et - 4 - Me₂CHL5、2,4,6 - Bu₃CHL6），它们可通过空间位阻和电子特性加以区分，这些化合物能与氯化钴轻松发生络合反应，形成相应的LCoCl螯合物Co1 - Co6。Co2和Co3的分子结构显示为正方锥几何构型，其不对称N,N,N'-配体的偕二甲基部分呈现环皱特征。在用甲基铝氧烷（MAO）或改性甲基铝氧烷（MMAO）活化后，所有钴配合物对乙烯聚合均表现出极高的活性，含均三甲苯基的Co4的活性水平高达每摩尔（Co）每小时1.19×10⁶克聚乙烯。值得注意的是，这些催化剂在高达70℃的温度下展现出最佳性能，同时还保持了可观的催化寿命，从而表现出良好的热稳定性。除了使用空间位阻最大的Co6（2,4,6 - 叔丁基）所得到的聚乙烯外，其他聚乙烯的分子量较低（M≤16.0 kg/mol）且分散度较窄（M̅w/M̅n≤3.4）。此外，对这些高度线性的聚合物蜡进行端基分析发现，存在不饱和以及不同程度的完全饱和材料的证据，这突出了β - H消除和链转移至铝作为终止途径的作用。
