A library of well-defined aminopyridine iron(II) precatalysts with a tertiary amine moiety have been prepared and serve as highly efficient precatalysts for polymerization of isoprene and other biobased conjugated dienes, delivering the corresponding polyolefin elastomers. These iron complexes were synthesized and further verified by ATR-IR, NMR, HR-MS spectroscopy, and elemental analysis. In addition, single-crystal diffraction analysis reveals that the structures of representative complexes Fe-Me, Fe-Et, and Fe-ⁱPr all displayed chloride-bridged centrosymmetric binuclear geometry. Upon activation with MAO, the aminopyridine iron(II) complexes formed homogeneous Ziegler–Natta catalyst systems, which possessed excellent activities for the polymerization of isoprene. Interestingly, the activity of precatalysts increased as the steric hindrance was enhanced (Fe-ⁱPr > Fe-Bn > Fe-Et), and the best activity was achieved by the Fe-ⁱPr complex (2.34 × 10⁶ g_polymer mol^–1 h^–1). In addition, the high activity that could almost be maintained even at 100 °C indicated that the Fe-ⁱPr catalyst showed excellent thermal stability. The polymerizations of biobased myrcene and β-farnesene have been achieved smoothly by the Fe-ⁱPr precatalyst, delivering high-molecular weight (≤4.9 × 10⁵ g/mol) “green rubber”.

中文翻译：

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增强氨基吡啶铁（II）催化共轭二烯聚合的热稳定性

已经制备了具有叔胺部分的明确定义的氨基吡啶铁（II）预催化剂库，其用作异戊二烯和其他生物基共轭二烯聚合的高效预催化剂，可提供相应的聚烯烃弹性体。合成了这些铁配合物，并通过ATR-IR，NMR，HR-MS光谱和元素分析进一步验证。此外，单晶衍射分析表明，代表性的配合物Fe-Me，Fe-Et和Fe- ⁱ Pr的结构全部显示出氯桥联的中心对称双核几何。经MAO活化后，氨基吡啶铁（II）络合物形成均相的齐格勒-纳塔催化剂体系，该体系具有出色的异戊二烯聚合活性。有趣的是，预催化剂的活性增加的空间位阻得到增强（铁-^我镨>的Fe-BN >的Fe-ET） ，和最佳的活性通过取得的Fe-^我镨复合物（2.34×10 ⁶克_聚合物摩尔^{- 1} h ^–1）。此外，即使在100°C时也几乎可以维持的高活性表明，Fe-^我镨催化剂表现出优异的热稳定性。Fe- ⁱ Pr预催化剂已顺利实现了生物基月桂烯和β-法呢烯的聚合，提供了高分子量（≤4.9×10 ⁵ g / mol）的“绿色橡胶”。