Achiral Lanthanide Alkyl Complexes Bearing N,O Multidentate Ligands. Synthesis and Catalysis of Highly Heteroselective Ring-Opening Polymerization of <i>rac</i>-Lactide
作者:Xinli Liu、Xiaomin Shang、Tao Tang、Ninghai Hu、Fengkui Pei、Dongmei Cui、Xuesi Chen、Xiabin Jing
DOI:10.1021/om0700359
日期:2007.5.1
found for complex 4. The Salan yttrium alkyl complex 6 was active but nonselective. Bis(alkyl) complexes 7 and 8 were more active than 1−3 toward polymerization of rac-LA, however, to afford atactic polylactides due to di-active sites. The ligand framework, especially the “bridge” between the two nitrogen atoms, played a significant role in governing the selectivity of the corresponding complexes via changing
氨基-氨基-双(酚)H 2 L 1的烷烃消除反应- 4,萨兰H 2 L 5和甲氧基-β-二亚胺HL 6,7用镧系元素的三(烷基)类,LN(CH 2森达3)3(THF)2(Ln为Y,Lu)中,分别得到了一系列的镧系元素络合物烷基1 - 8以四甲基硅烷的释放。配合物1 - 6是THF溶剂化的单(烷基)S按稳定的O,N,N,O -tetradentate配体。配合物1 - 3和5采用扭曲的八面体几何形状,而4包含四方双锥芯。带有单阴离子部分L 6(L 7),配合物7(8)是不含THF的双(烷基)。在配合物7中,O,N,N-三齿配体与两个烷基物质结合形成四面体配位核心。配合物1,2,和3显示适度的活性,但是高立体选择性为聚合外消旋-丙交酯,得到聚乳酸杂同与单体单元的外消旋enchainment P ř范围从0.95至0.99,达到迄今的最高值。复杂5表现出几乎相同的活性水平,尽管选择性相对较低。相