Exploring the impact of abnormal coordination in macrocyclic N-heterocyclic carbene ligands on bio-inspired iron epoxidation catalysis

IF 4.4 3区化学 Q2 CHEMISTRY, PHYSICAL

Catalysis Science & Technology Pub Date : 2024-09-12 DOI:10.1039/d4cy00992d

Greta G. Zámbó, Carla A. Esslinger, Michael J. Sauer, Isabelle Rüter, Robert M. Reich, Serhiy Demeshko, Franc Meyer, Fritz E. Kühn

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Abstract

The first macrocyclic abnormal N-heterocyclic carbene (aNHC) Fe^III complex, featuring a calix[4]3-methyl-1,2,3-triazole-5-ylidene ligand system is synthesised and characterised inter alia via EA, SC-XRD, NMR and UV/vis spectroscopy. Including Mössbauer spectroscopy, SQUID and DFT calculations, the impact of the aNHC on the Fe^III complex and its corresponding Fe^II derivative is investigated. A comprehensive study of the aNHC Fe complexes in their performance in homogenous epoxidation reactions is reported and compared to the established benchmark catalysts. The complexes demonstrate efficient and selective catalytic activity in the epoxidation of cis-cyclooctene with H₂O₂, with TOFs up to almost 60 000 h⁻¹. Additionally, the epoxidation of more challenging olefinic substrates is possible. The reactivity under oxidative conditions of both complexes is investigated. NMR measurements reveal the formation of a mono-oxidised triazole ligand as degradation product. HR-ESI-MS measurements, supported by DFT calculations indicate the formation of an oxoiron species.

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探索大环 N-杂环碳烯配体的异常配位对生物启发铁环氧化催化的影响

通过 EA、SC-XRD、NMR 和 UV/vis 光谱等方法，合成并表征了以钙[4]3-甲基-1,2,3-三唑-5-亚基配体系统为特征的首个大环异常 N-heterocyclic carbene (aNHC) FeIII 复合物。通过莫斯鲍尔光谱、SQUID 和 DFT 计算，研究了 aNHC 对 FeIII 复合物及其相应的 FeII 衍生物的影响。报告全面研究了 aNHC Fe 复合物在均质环氧化反应中的性能，并将其与已建立的基准催化剂进行了比较。这些配合物在顺式环辛烯与 H2O2 的环氧化反应中表现出高效和选择性催化活性，TOFs 可高达近 60 000 h-1。此外，还可以对更具挑战性的烯烃底物进行环氧化反应。我们研究了这两种复合物在氧化条件下的反应活性。核磁共振测量显示，降解产物是一种单氧化三唑配体。经 DFT 计算支持的 HR-ESI-MS 测量结果表明形成了一种氧化铁。

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来源期刊

Catalysis Science & Technology CHEMISTRY, PHYSICAL-

CiteScore

8.70

自引率

6.00%

发文量

587

审稿时长

1.5 months

期刊介绍： A multidisciplinary journal focusing on cutting edge research across all fundamental science and technological aspects of catalysis. Editor-in-chief: Bert Weckhuysen Impact factor: 5.0 Time to first decision (peer reviewed only): 31 days