Ge You, Li Shuaikang, Fan Weigang, Dai Shengyu
Institutes of Physical Science and Information Technology, Key Laboratory of Structure and Functional Regulation of Hybrid Materials of Ministry of Education, Anhui University, Hefei, Anhui 230601, China.
Inorg Chem. 2021 Apr 19;60(8):5673-5681. doi: 10.1021/acs.inorgchem.0c03715. Epub 2021 Mar 30.
8-Arylnaphthyl substituents are privileged motifs frequently integrated into late-transition-metal catalysts, endowing them with an ability to retard chain transfer in ethylene polymerization. In this contribution, we disclose a sort of novel α-diiminenickel and -palladium complexes containing flexible 8-alkylnaphthyl in lieu of rigid 8-arylnaphthyl and their catalytic performance in ethylene polymerization. An interesting feature of these 8-alkylnaphthyl-substituted α-(diimine)PdMeCl complexes is that they present as a mixture of syn and anti isomers (syn:anti = ca. 1:1 ratio, determined by H and C NMR spectroscopy). In ethylene polymerization, these nickel complexes displayed high activity (up to 3.37 × 10 g mol h) and generated branched polyethylenes with broad or bimodal molecular weight distributions (4.6-29.3), while the corresponding palladium complexes exhibited moderate activity, producing highly branched polyethylenes with unimodal and narrow molecular weight distributions (<1.8). In ethylene (E)/methyl acrylate (MA) copolymerization, highly branched E-MA copolymers with considerable MA incorporations were achieved by these palladium complexes. Most interestingly, compared to rigid 8-arylnaphthyl-substituted α-diiminenickel and -palladium complexes, the flexible 8-alkylnaphthyl ones showed significantly improved activity and generated lower or comparable molecular weight polyethylenes or E-MA copolymers.
8-芳基萘基取代基是常用于后期过渡金属催化剂的优势结构单元，使这些催化剂具有抑制乙烯聚合链转移的能力。在本论文中，我们报道了一类新型的α-二亚胺镍和钯配合物，其中含有柔性的8-烷基萘基而非刚性的8-芳基萘基，并研究了它们在乙烯聚合反应中的催化性能。这些8-烷基萘基取代的α-(二亚胺)PdMeCl配合物的一个有趣特点是，它们以顺式和反式异构体的混合物形式存在（顺式:反式 = 约1:1比例，通过氢谱和碳谱确定）。在乙烯聚合反应中，这些镍配合物表现出高活性（高达3.37×10⁶ g mol⁻¹ h⁻¹），生成具有宽或双峰分子量分布（4.6 - 29.3）的支化聚乙烯，而相应的钯配合物活性适中，生成具有单峰和窄分子量分布（<1.8）的高度支化聚乙烯。在乙烯（E）/丙烯酸甲酯（MA）共聚反应中，这些钯配合物实现了具有相当MA掺入量的高度支化E-MA共聚物。最有趣的是，与刚性的8-芳基萘基取代的α-二亚胺镍和钯配合物相比，柔性的8-烷基萘基取代的配合物显示出显著提高的活性，并生成分子量更低或相当的聚乙烯或E-MA共聚物。
