双核胺亚胺铝配合物的合成、结构及其在ε-己内酯开环聚合中的应用

Dinuclear aluminum complexes bearing anilido-aldimine ligands: synthesis, structures, and ring-opening polymerization catalysis of ε-caprolactone

摘要:

利用四齿胺亚胺配体(1R,2R)-[(NHAr)C6H4CH=N]2C6H10 (Ⅱ: Ar = 苯基，Ⅲ: Ar = 2,6-二甲基苯基)与三甲基铝反应得到双核胺亚胺铝配合物(Ⅳ、Ⅴ)。利用核磁共振氢谱、碳谱和SC-XRD对配合物Ⅳ、Ⅴ结构进行表征，证实配合物Ⅳ、Ⅴ具有单配体双金属中心结构。利用Ⅳ、Ⅴ在苄醇的存在下催化ε-己内酯开环聚合制备聚己内酯，并对反应条件进行了优化。结果表明，当n(ε-己内酯)∶n(BnOH)∶n(Ⅳ or Ⅴ) = 200∶4∶1时，在1.5 min内ε-己内酯转化率超过97%，转化频率（Ⅳ：7840 h–1；Ⅴ：9700 h–1），远高于乙基桥联双核铝配合物(1152 h–1)和单核胺亚胺铝配合物(2550 h–1)；得到的聚合物相对分子质量可控，聚合反应具有活性聚合的特点。

Abstract:

The anilido-aldimine chelating ligands (1R,2R)-[(NHAr)C6H4CH=N]2C6H10 (Ⅱ: Ar = C6H5; Ⅲ: Ar = 2,6-Me2C6H3) reacted with Al(CH3)3 to afford dinuclear aluminum complexes (Ⅳ, Ⅴ), respectively. All the complexes were characterized by 1H and 13C NMR spectroscopies. Complex Ⅴ was additionally characterized by single crystal X-ray diffraction analyses. The X-ray analysis reveals that the molecular contains two aluminum centrals and single ligand. Catalysis of the aluminum complexes Ⅳ, Ⅴ towards the ring-opening polymerization of ε-caprolactone was investigated in the presence of benzyl alcohol. All the polymerization reactions proceed in a controlled/living manner. The conversion exceeds 97% within 1.5 min using n(ε-caprolactone)∶n(BnOH)∶n(Ⅳ or Ⅴ) =200∶4∶1. Turn over frequency for Ⅳ is 7840 h–1, and for Ⅴ is 9700 h–1, much higher than the ethyl-bridged binuclear aluminum complex (1152 h-1) and the mononuclear amine-imine aluminum complex (2550 h-1). The polymerization reactions proceed in a controlled manner.