State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University, Lanzhou, 730000, P. R. China.
Chem Asian J. 2019 Mar 1;14(5):662-669. doi: 10.1002/asia.201801834. Epub 2019 Feb 13.
Two sodium/potassium tetradentate aminobisphenolate ion-paired complexes were synthesized and structurally characterized. These ion-paired complexes are efficient catalysts for the ring-opening polymerization of rac-lactide (rac-LA) in the presence of 5 equivalents BnOH as an initiator and the side reaction of epimerization can be suppressed well at low temperatures. The polymerizations are controllable, affording polylactides with desirable molecular weights and narrow molecular weight distributions; the highest molecular weight can reach 50.1 kg mol in this system, and a best isoselectivity of P =0.82 was achieved. Such polymerizations have rarely been reported for isoselective sodium/potassium complexes without crown ether as an auxiliary ligand. The solid structures suggest that BnOH can be activated by an interaction with the anion of sodium/potassium complex via a hydrogen bond and that the monomer is activated by coordination to sodium/potassium ion.
合成并结构表征了两种钠/钾四齿氨基双双酚盐离子对配合物。在 5 当量 BnOH 引发剂存在下，这些离子对配合物是 rac-丙交酯（rac-LA）开环聚合的高效催化剂，并且低温下可以很好地抑制差向异构化的副反应。聚合反应可控，可得到具有理想分子量和较窄分子量分布的聚乳酸；在该体系中，最高分子量可达 50.1kg/mol，达到了最好的等规选择性 P=0.82。在没有冠醚作为辅助配体的情况下，对于非手性钠/钾配合物，这样的聚合反应很少有报道。固体结构表明，BnOH 可以通过氢键与钠/钾配合物的阴离子相互作用而被激活，单体可以通过与钠/钾离子配位而被激活。
