This is a comprehensive study of the effects of rationally designed hemilabile ligands on the stability, reactivity, and change in catalytic behavior of indium complexes. We report cationic alkyl indium complexes supported by a family of hemi-salen type ligands bearing hemilabile thiophenyl (2a), furfuryl (2b) and pyridyl (2c) pendant donor arms. Shelf-life and stability of these complexes followed the trend 2a < 2b < 2c, showing direct correlation to the affinity of the pendant donor group to the indium center. Reactivity towards polymerization of epichlorohydrin and cyclohexene oxide followed the trend 2a > 2b > 2c with control of polymerization following an inverse relationship to reactivity. Surprisingly, 2c polymerized racemic lactide without an external initiator, likely through an alkyl-initiated coordination-insertion mechanism.

中文翻译：

---

用于开环聚合的阳离子铟催化剂：调节与半不稳定配体的反应性

这是对合理设计的半不稳定配体对铟配合物的稳定性，反应性和催化行为变化的影响的综合研究。我们报告阳离子烷基铟配合物，由半不稳定的salen型配体家族支撑，这些配体带有半不稳定的噻吩基（2a），糠基（2b）和吡啶基（2c）侧链供体。这些配合物的保质期和稳定性遵循2a < 2b < 2c趋势，表明与侧基供体基团与铟中心的亲和力直接相关。对环氧氯丙烷和氧化环己烯的聚合反应性遵循趋势2a > 2b > 2c在与反应性成反比关系后控制聚合。出人意料的是，2c聚合了外消旋丙交酯而没有外部引发剂，这很可能是通过烷基引发的配位插入机制。