摘要
For transition metal-based olefin polymerization catalysts, ligand steric and electronic effects can strongly influence important catalytic properties. However, the simultaneous tuning of both steric and electronic effects has not been explored in most of the previous studies. In this contribution, a strategy to tune the ligand electronic and steric effects in a concerted fashion is reported. In such a system, both dibenzhydryl groups and multiple methoxy/fluoro groups were installed in α-diimine ligands. In addition to strongly influencing ligand electronics, the methoxy/fluoro groups can interact with the dibenzhydryl groups and efficiently increase ligand sterics. In ethylene polymerization, this concurrent tuning of electronic and steric effects can lead to simultaneous enhancement of several parameters(activity, stability, polymer molecular weight, melting point, branching density) for both the nickel and palladium catalysts. The effectiveness of this strategy is highly attractive for future studies in other catalytic systems.
对于过渡金属配合物类的烯烃聚合催化剂,配体的位阻和电子效应能够显著影响其主要的催化性能.然而,对于位阻和电子效应的同时调节在以往的研究中鲜有涉及.本文报道了一种以协同方式调节配体结构中的电子和位阻效应的策略.含有二苯甲基取代基的α-二亚胺配体中,在苯胺结构的3,4,5-位分别引入三个供电子的甲氧基或三个吸电子的氟取代基.上述甲氧基和氟取代基的引入,不仅能够有效调节配体的电子效应,还能够通过甲氧基或氟取代基与二苯甲基之间的空间排斥作用,有效增加配体的空间位阻.在乙烯聚合中,这种电子和位阻效应的协同作用的引入,能够实现改进镍和钯催化剂的几种重要的催化性能参数,包括催化活性、催化剂稳定性以及所得聚合物的分子量、熔点、支化密度.该位阻和电子效应协同的策略在将来很有可能被用于其他催化领域.
作者
Qasim Muhammad
Chen Tan
Changle Chen
Qasim Muhammad;谭忱;陈昶乐(Key Laboratory of Soft Matter Chemistry,Department of Polymer Science and Engineering,University of Science and Technology of China,Hefei 230026,China;Institutes of Physical Science and Information Technology,Anhui University,Hefei 230601,China)
基金
supported by the National Natural Science Foundation of China (21690071 and 21871242)
the Fundamental Research Funds for the Central Universities.
