A series of cobalt(II) complexes bearing 3-aryliminomethyl-2-hydroxybenzaldehydes (tridentate [NOO] ligands) was prepared and characterized by FT-IR and elemental analysis along with single-crystal X-ray diffraction. The X-ray diffraction analysis revealed that a dinuclear centrosymmetrical structure formed, in which each cobalt atom is surrounded by two bridged ligands and two acetate groups as a distorted octahedron. These dinuclear cobalt complexes displayed high catalytic activities for the polymerization of 1,3-butdiene on activation with organoaluminum cocatalysts to yield cis-1,4-polybutadiene with high selectivity. Ethylaluminum sesquichloride (EASC) was found to be the most efficient cocatalyst resulting in high conversion of butadiene and cis-1,4 content in the polymers with moderate molecular weight. The high catalytic activity and stereoselectivity could be achieved in a wide range of reaction conditions. All the dinuclear cobalt complexes (C1–C6) yielded predominantly cis-1,4-polybutadienes (> 96%) with negligible amounts of trans-1,4 (< 2.4%) and 1,2-vinyl (< 1.5%) products under the Al/Co molar ratio of 80 at 25 °C. The ligand modification by varying the substituents at the 4-position of phenol and on the imino-N aryl ring showed slight influence on the catalytic activity and microstructure of the resulting polymers.
制备了一系列带有 3-芳基亚
氨基甲基-2-羟基
苯甲醛(三叉 [NOO]
配体)的
钴(II)配合物,并通过傅立叶变换红外光谱、元素分析和单晶 X 射线衍射进行了表征。X 射线衍射分析表明,形成了一种双核中心对称结构,其中每个
钴原子都被两个桥接
配体和两个
醋酸基团包围,形成一个扭曲的八面体。这些双核
钴配合物在与
有机铝助催化剂活化聚合
1,3-丁二烯时显示出很高的催化活性,能以高选择性生成顺式-
1,4-聚丁二烯。研究发现,乙基倍半
氯化铝(EASC)是最有效的助催化剂,可实现
丁二烯的高转化率和聚合物中顺式-1,4 的含量,且分子量适中。高催化活性和立体选择性可在多种反应条件下实现。在铝/
钴摩尔比为 80、温度为 25 ℃ 的条件下,所有双核
钴配合物(C1-C6)主要生成顺式-
1,4-聚丁二烯(> 96%),反式-1,4(< 2.4%)和 1,2-乙烯基(< 1.5%)产物的含量微乎其微。通过改变苯酚 4 位和亚胺-N 芳基环上的取代基对
配体进行修饰,对催化活性和所得聚合物的微观结构产生了轻微影响。