Abstract

A series of asymmetric mono(imine)pyrroles (L1–L5) is synthesized using 2-acetylpyrrole and a series of dimethylanilines which have two methyl groups at different positions of the aniline ring. A simplified synthetic method is utilized to prepare the corresponding nickel complexes (1-5) with direct condensation of the mono(imine)pyrrole ligand and nickel chloride. All compounds are well characterized by EA, IR, ¹H NMR, UV-Vis, XRD and TGA. XRD shows that all the ligands have similar geometries. XRD of 2 indicates that it has a tetra-coordinated geometry in which the ligand is chelated to the nickel center in a 2:1 molar ratio. The density functional theory (DFT) calculations of nickel complexes are performed at the B3LYP/3-21G level to obtain the total energy and the optimized molecular geometry. The calculation results are in agreement with the experimental data. This series of nickel complexes can effectively catalyze the polymerization of MMA in the presence of azodiisobutyronitrile (AIBN). The polymerization temperature and time, as well as the complex structure, influence to some extent the catalytic performance. By the orthogonal experimental design the polymerization reaction conditions are optimized. Under the optimum conditions of 100 °C and 10 h, complex 1 shows an excellent MMA polymerization catalytic activity of 9.861·10⁴ g/mol·h, and a relatively higher molecular weight (M_n = 108798 g/mol) with a narrower molecular mass distribution (PDI = 2.2305).

中文翻译：

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不对称单（亚胺）吡咯镍 PMMA 催化剂：合成、晶体结构和 DFT 计算

摘要

使用 2-乙酰基吡咯和一系列在苯胺环的不同位置具有两个甲基的二甲基苯胺合成了一系列不对称单（亚胺）吡咯 ( L1 – L5 )。简化合成方法用于制备相应的镍络合物（1 - 5）与所述单（亚胺）直接缩合的吡咯配体和氯化镍。所有化合物均通过 EA、IR、¹ H NMR、UV-Vis、XRD 和 TGA 进行了充分表征。XRD 显示所有配体具有相似的几何形状。2的XRD表明它具有四配位几何结构，其中配体以 2:1 的摩尔比螯合到镍中心。镍配合物的密度泛函理论 (DFT) 计算在 B3LYP/3-21G 水平上进行，以获得总能量和优化的分子几何形状。计算结果与实验数据一致。该系列镍配合物可在偶氮二异丁腈（AIBN）存在下有效催化MMA的聚合。聚合温度和时间以及复杂的结构在一定程度上影响催化性能。通过正交实验设计优化了聚合反应条件。在 100 ℃ 10 h 的最佳条件下，配合物1显示出9.861·10 ⁴  g/mol·h的优异MMA聚合催化活性，以及相对较高的分子量( M _n  = 108798 g/mol)和较窄的分子量分布(PDI = 2.2305)。