Jia Yihong, ALOthman Asma A, Liang Rui, Li Xiaoyong, Ouyang Weiyi, Wang Xiangdong, Wu Yong, Osman Sameh M, Li Zhaorui, Gao Min, Sun Yang
Department of Applied Chemistry, School of Science, Xi'an Jiaotong University, No. 28, Xianning West Road, Xi'an 710049, China.
Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
Materials (Basel). 2020 Oct 29;13(21):4860. doi: 10.3390/ma13214860.
A series of oligomeric (salen)Mn(III) complexes featuring tartrate linkers were prepared and immobilized over layered double hydroxide, and then used as catalysts for asymmetric epoxidation of unfunctionalized olefins. Comprehensive characterizations including H NMR, FT-IR, UV-Vis, elemental analysis, GPC, and ICP-AES were used to illustrate structures of oligomeric (salen)Mn(III) complexes, while powdered XRD, nitrogen physisorption, together with XPS studies provided further details to detect structures of heterogeneous catalysts. Interestingly, scanning electron microscopy found an interesting morphology change during modification of layered supporting material. Catalytic experiments indicated that configuration of major epoxide products was determined by salen chirality more than that of tartrate linker, but enantioselectivity (e.e. values) could be enhanced when tartrate and salen showed identical chiral configurations. Furthermore, the ()-salen moieties linked with ()-tartrate spacers usually offered higher enantioselectivity compared to other combinations. Lastly, Zn(II)/Al(III) layered double hydroxide played as a rigid supporting material in catalysis, showing positive chiral induction and high recycling potential in catalytic reactions.
制备了一系列具有酒石酸酯连接基的低聚（salen）Mn（III）配合物，并将其固定在层状双氢氧化物上，然后用作未官能化烯烃不对称环氧化的催化剂。使用包括¹H NMR、FT-IR、UV-Vis、元素分析、GPC和ICP-AES在内的综合表征方法来说明低聚（salen）Mn（III）配合物的结构，而粉末XRD、氮物理吸附以及XPS研究则提供了更多细节以检测多相催化剂的结构。有趣的是，扫描电子显微镜发现在层状载体材料改性过程中出现了有趣的形态变化。催化实验表明，主要环氧化物产物的构型更多地由salen手性而非酒石酸酯连接基的手性决定，但当酒石酸酯和salen显示相同的手性构型时，对映选择性（e.e.值）可以提高。此外，与其他组合相比，与（-）-酒石酸酯间隔基相连的（-）-salen部分通常具有更高的对映选择性。最后，Zn（II）/Al（III）层状双氢氧化物在催化中作为刚性载体材料，在催化反应中显示出正的手性诱导和高循环潜力。
