α-二亚胺钴配合物催化1,3-丁二烯高活性与高顺式-1,4选择性聚合

合成了一系列α-二亚胺钴配合物ArN=C(Me)-(Me)C=NAr]CoCl₂(Ar=C₆H₅, 3a; 4-MeC₆H₄, 3b; 4-MeOC₆H₄, 3c; 4-FC₆H₄, 3d; 4-ClC₆H₄, 3e; 2-MeC₆H₄, 3f; 2-EtC₆H₄, 3g; 2-ⁱPrC₆H₄, 3h; 2,4,6-Me₃C₆H₂, 3i; 2,6-Et₂C₆H₃, 3j; 2,6-ⁱPrC₆H₃, 3k)和作为对比的吡啶双亚胺二氯化钴配合物(4a), 并用X射线单晶衍射方法研究了配合物3i, 3k和4a的分子结构. α-二亚胺钴配合物在倍半乙基氯化铝的作用下对丁二烯聚合有较高的催化活性,得到的顺式-1,4结构含量达98%,且有较高分子量(M_n≈1×10⁴-1×10⁵)的聚丁二烯. 配体的电子效应影响催化剂的活性及顺式-1,4选择性, 而配体的空间位阻对丁二烯聚合几乎没有影响. 详细研究了聚合时间、聚合温度、烷基铝助催化剂及铝比等条件对丁二烯聚合行为的影响.

Highly active and cis-1,4 selective polymerization of 1,3-butadiene catalyzed by cobalt(II) complexes bearing α-diimine ligands

A series of cobalt(II) complexes bearing α-diimine ligands were synthesized and characterized by elemental and spectroscopic analysis. These complexes had the general formulas ArN=C(Me)-(Me)C=NAr]CoCl₂ (Ar=C₆H₅, 3a; 4-MeC₆H₄, 3b; 4-MeOC₆H₄, 3c; 4-FC₆H₄, 3d; 4-ClC₆H₄, 3e; 2-MeC₆H₄, 3f; 2-EtC₆H₄, 3g; 2-ⁱPrC₆H₄, 3h; 2,4,6-Me₃C₆H₂, 3i; 2,6-Et₂C₆H₃, 3j; 2,6-ⁱPrC₆H₃, 3k). 2,6-Bis(2,6-diisopropylphenylimino)ethyl]pyridine CoCl₂ (4a) was also synthesized for comparison. The structures of complexes 3i, 3k, and 4a were further analyzed by X-ray crystallography. When the Co(II) complexes were activated with ethylaluminum sesquichloride, they exhibited high catalytic activity for 1,3-butadiene polymerization. The polymers produced have high cis-1,4 stereoregularity (up to 98.0%) and high molecular weights (M_n=1×10⁴-1×10⁵). The substituent ligand affected both catalytic activity and stereoselectivity through an electronic effect while steric hindrance by the substituent was not important. The effects of the polymerization conditions, such as polymerization time, temperature, different alkylaluminum compounds used as cocatalyst, and Al]/Co] molar ratio, on polymerization behavior were investigated.