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IronIII Half Salen Catalysts for Atom Transfer Radical and Ring-Opening Polymerizations
ACS Omega ( IF 3.7 ) Pub Date : 2018-12-10 00:00:00 , DOI: 10.1021/acsomega.8b02432 Eszter Fazekas 1 , Gary S. Nichol 1 , Jennifer A. Garden 1 , Michael P. Shaver 1
ACS Omega ( IF 3.7 ) Pub Date : 2018-12-10 00:00:00 , DOI: 10.1021/acsomega.8b02432 Eszter Fazekas 1 , Gary S. Nichol 1 , Jennifer A. Garden 1 , Michael P. Shaver 1
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A series of monometallic pentacoordinate FeIII chloride complexes have been prepared and characterized by high-resolution mass spectrometry and elemental analysis. X-ray diffraction analysis showed that the bis-chelated FeIII complexes bear distorted trigonal bipyramidal geometries. The air- and moisture-stable FeIII complexes were screened as mediators in the reverse atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate. Moderate to excellent control was achieved with dispersities as low as 1.1 for both poly(methyl methacrylate) and polystyrene. Kinetic studies showed living characteristics, and end group analysis revealed the presence of olefin-terminated polymer chains, suggesting catalytic chain transfer as a competing polymerization mechanism. Although the catalysts are not the fastest Fe ATRP mediators, they are robust and flexible. Using propylene oxide as an initiator, the complexes were active catalysts for the ring-opening polymerization of rac-lactide with moderate control. While the addition of propylene oxide has been reported as an efficient method of converting a metal–halide bond to a metal–alkoxide bond in situ, we show herein that this initiation mechanism can limit polymerization reproducibility and introduce an induction period.
中文翻译：
铁III半塞伦催化剂用于原子转移自由基和开环聚合
制备了一系列单金属五配位的Fe III氯化物配合物，并通过高分辨率质谱和元素分析对其进行了表征。X射线衍射分析表明，双螯合的Fe III配合物具有扭曲的三角双锥体几何形状。空气和水分稳定的Fe III在苯乙烯和甲基丙烯酸甲酯的反向原子转移自由基聚合（ATRP）中，筛选了配合物作为介体。对于聚（甲基丙烯酸甲酯）和聚苯乙烯，分散度均低至1.1，可实现中度至优异的控制。动力学研究表明其活性特征，端基分析表明存在以烯烃为末端的聚合物链，这表明催化链转移是竞争性聚合机理。尽管这些催化剂不是最快的Fe ATRP介体，但它们既坚固又灵活。使用环氧丙烷作为引发剂，该配合物是rac开环聚合的活性催化剂-丙交酯适度控制。尽管已经报道了环氧丙烷的添加是一种将金属卤化物键原位转化为金属烷氧基键的有效方法，但我们在此表明，这种引发机理会限制聚合反应的可重复性并引入诱导期。
更新日期：2018-12-10
中文翻译：
铁III半塞伦催化剂用于原子转移自由基和开环聚合
制备了一系列单金属五配位的Fe III氯化物配合物，并通过高分辨率质谱和元素分析对其进行了表征。X射线衍射分析表明，双螯合的Fe III配合物具有扭曲的三角双锥体几何形状。空气和水分稳定的Fe III在苯乙烯和甲基丙烯酸甲酯的反向原子转移自由基聚合（ATRP）中，筛选了配合物作为介体。对于聚（甲基丙烯酸甲酯）和聚苯乙烯，分散度均低至1.1，可实现中度至优异的控制。动力学研究表明其活性特征，端基分析表明存在以烯烃为末端的聚合物链，这表明催化链转移是竞争性聚合机理。尽管这些催化剂不是最快的Fe ATRP介体，但它们既坚固又灵活。使用环氧丙烷作为引发剂，该配合物是rac开环聚合的活性催化剂-丙交酯适度控制。尽管已经报道了环氧丙烷的添加是一种将金属卤化物键原位转化为金属烷氧基键的有效方法，但我们在此表明，这种引发机理会限制聚合反应的可重复性并引入诱导期。
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