A series of iron(III) chloride complexes based upon Schiff base framework have been synthesized and characterized by mass spectra, elemental analysis, and X-ray crystallography. These bench-stable complexes were for the first time capable as highly efficient catalysts for lactide and ε-caprolactone polymerization in the presence of propylene oxide (PO), greatly surpassing conventional aluminum analogies. Electron-withdrawing substituents as well as elevated temperature boosted the activity while a bulky group on salicylaldehyde moieties abnormally produces the same effect, whereas rigid backbone retarded the reactivity. Polylactide tactics ranging from isotactic to hererotactic enchainment were obtained by tuning the ligand backbone and substituents. The stereoselectivity was confirmed to proceed via a chain-end control mechanism by kinetic studies using different isomers of lactide, and the overall polymerization process was also investigated in detail by the oligomer mass spectrum as well as end group (−OCHMeCH₂Cl) analysis of polymer via ¹H, ¹³C, and two-dimensional (2-D) NMR characterizations.

中文翻译：

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稳定的Salen-铁络合物：通过原位引发丙交酯和ε-己内酯聚合的立体选择性催化剂

合成了一系列基于席夫碱骨架的氯化铁（III）配合物，并通过质谱，元素分析和X射线晶体学进行了表征。这些稳定的配合物首次在环氧丙烷（PO）的存在下成为丙交酯和ε-己内酯聚合反应的高效催化剂，大大超越了常规的铝类似物。吸电子取代基以及升高的温度提高了活性，而水杨醛部分上的庞大基团异常地产生了相同的作用，而刚性主链则阻碍了反应性。通过调节配体主链和取代基，可以获得从等规链到等规链的聚丙交酯策略。通过¹ H，¹³ C和二维（2-D）NMR表征对聚合物进行₂ Cl）分析。