Guo Liwei, Zada Muhammad, Zhang Wenjuan, Vignesh Arumugam, Zhu Dongzhi, Ma Yanping, Liang Tongling, Sun Wen-Hua
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 Apr 23;48(17):5604-5613. doi: 10.1039/c9dt01109a.
A novel family of 2,6-bis[1-(p-dibenzocycloheptylarylimino)ethyl]pyridylcobalt dichlorides Co1-Co4 were synthesized and fully characterized by FT-IR, 1H NMR, and elemental analysis as well as X-ray diffraction analysis. The 1H NMR spectra of these paramagnetic cobalt complexes Co1-Co3 showed similar spectra with one set of signals, while Co4 possessed two sets of signals due to the different conformations caused by different substituents on the ortho-position of the N-aryl group. Crystal structures of Co1, Co2 and Co4 revealed similar square-pyrimidal geometry around the cobalt ion, in which two dibenzocycloheptyl groups adapted as cis-conformers, whereas Co3 possessed bistrigonal geometry and the two dibenzocycloheptyl groups were adapted as trans-conformers. On activation with methylaluminoxane (MAO) or modified MAO (MMAO), all these cobalt complexes displayed high catalytic activities towards ethylene polymerization (up to 1.21 × 107 g (PE) mol-1 (Co) h-1) and produced polyethylenes with narrow molecular distributions (PDI ≈ 2.0). Co3 bearing bulkier isopropyl substituents on the ortho-position gave much higher molecular weight of resultant polyethylene than the other cobalt complexes reported herein. The microstructure analysis of the PEs demonstrated that they are highly linear and contain a vinyl end group as the major group and saturated methyl as the minor group, in which the content of the unsaturated polymer chain relied on the ortho-substituent of the N-aryl group.
合成了一个新型的2,6 - 双[1 - (对 - 二苯并环庚基芳基亚氨基)乙基]吡啶二氯化钴家族Co1 - Co4，并通过傅里叶变换红外光谱（FT - IR）、核磁共振氢谱（1H NMR）、元素分析以及X射线衍射分析对其进行了全面表征。这些顺磁性钴配合物Co1 - Co3的1H NMR谱显示出相似的单组信号谱，而Co4由于N - 芳基邻位不同取代基导致的不同构象，具有两组信号。Co1、Co2和Co4的晶体结构显示钴离子周围具有相似的方锥几何构型，其中两个二苯并环庚基基团呈顺式构象，而Co3具有双三角几何构型，两个二苯并环庚基基团呈反式构象。在用甲基铝氧烷（MAO）或改性甲基铝氧烷（MMAO）活化后，所有这些钴配合物对乙烯聚合均表现出高催化活性（高达1.21×107 g（PE）mol-1（Co）h-1），并生成了具有窄分子量分布（PDI≈2.0）的聚乙烯。在邻位带有较大异丙基取代基的Co3生成的聚乙烯分子量比本文报道的其他钴配合物高得多。对聚乙烯的微观结构分析表明，它们高度线性，主要基团为乙烯基端基，次要基团为饱和甲基，其中不饱和聚合物链的含量取决于N - 芳基的邻位取代基。
