Heteroscorpionate Rare-Earth Metal Zwitterionic Complexes: Syntheses, Characterization, and Heteroselective Catalysis on the Ring-Opening Polymerization of rac-Lactide
作者:Zhichao Zhang、Dongmei Cui
DOI:10.1002/chem.201102074
日期:2011.10.4
with heterotacticity up to 0.87. However, the zwitterionic complexes 6 were less active and less selective than 5, which might be on account of the stronger coordination of the tetradentate ligand. Complexes 5 represent rare examples of the selective ROP of rac‐LA mediated by rare‐earth metal complexes supported by non‐bisphenolate ligands.
首次合成了新型中性膦修饰的异蝎子配体(3,5-Me 2 Pz)2 CHPPh 2(1)及其衍生物氧代膦(2)和亚氨基膦(3)杂蝎子。这些中性的异蝎子配体对稀土金属三(烷基)[Ln(CH 2 SiMe 3)3(thf)2 ](Ln = Y,Lu,Sc)表现出独特的化学作用。化合物1与[Ln(CH 2 SiMe 3)3(thf)2]提供了杂蝎子稀土金属三烷基加合物的络合物4 a – c。化合物2和3用[Ln(CH 2 SiMe 3)3(thf)2 ]处理,分别得到了空前的两性离子杂蝎子稀土金属二烷基5和6。在此过程中,杂甲酸盐通过次甲基CH键断裂而转移到碳负离子上,这是由于存在吸电子基团引起的。另外,配体和中心金属对配合物的催化活性和比选择性均表现出协同作用。4 – 6用于外消旋丙交酯(rac -LA)的开环聚合(ROP )。所有加合物络合物4都是非选择性的,并给出无规立构聚丙交酯(PLA)