Ganesan Vinothkumar, Yoon Sungho
Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Heukseok-dong, Dongjak-gu, Seoul, Republic of Korea 06974.
Inorg Chem. 2020 Mar 2;59(5):2881-2889. doi: 10.1021/acs.inorgchem.9b03247. Epub 2020 Feb 12.
Salen and salphens are important ligands in coordination chemistry due to their ability to form various metal complexes that can be used for a variety of organic transformations. However, salen/salphen complexes are difficult to separate from the reaction mixture, thereby limiting their application to homogeneous systems. Accordingly, considerable effort has been spent to heterogenize the metallosalen/salphen complexes; however, this has resulted in compromised activities and selectivities. Direct heterogenization of metallosalens to form porous organic polymers (POPs) shows promise for heterogeneous catalysis, because it would allow easy separation while retaining catalytic function. Thus, a facile synthetic strategy for preparing metallosalen/salphen-based porous organic polymers through direct molecular knitting using a Friedel-Crafts reaction is presented herein for the first time. As representative candidates, salphenM(III)Cl (M = Al and Cr) complexes are knitted by covalent cross-linking using this facile, scalable, one-pot method to synthesize highly POPs in high yields. When incorporated with [Co(CO)] anions, the resulting heterogeneous Lewis acidic metal (Al and Cr) POPs exhibit propylene oxide ring-expansion carbonylation activity on par with those of their homogeneous counterparts.
由于具有形成各种金属配合物的能力，这些配合物可用于多种有机转化反应，萨伦（Salen）和萨芬（salphens）是配位化学中重要的配体。然而，萨伦/萨芬配合物很难从反应混合物中分离出来，从而限制了它们在均相体系中的应用。因此，人们花费了大量精力使金属萨伦/萨芬配合物多相化；然而，这导致了活性和选择性的降低。将金属萨伦直接多相化以形成多孔有机聚合物（POPs）显示出在多相催化方面的潜力，因为这既能实现轻松分离，又能保留催化功能。因此，本文首次提出了一种通过傅克反应直接分子编织制备基于萨伦/萨芬的多孔有机聚合物的简便合成策略。作为代表性的候选物，使用这种简便、可扩展的一锅法通过共价交联将萨芬M(III)Cl（M = Al和Cr）配合物编织在一起，以高产率合成高度多孔的有机聚合物。当与[Co(CO)]阴离子结合时，所得的多相路易斯酸性金属（Al和Cr）多孔有机聚合物表现出与均相对应物相当的环氧丙烷扩环羰基化活性。
