Degradation pathways of a highly active iron(iii) tetra-NHC epoxidation catalyst. Issue 3 (19th January 2021)

• Record Type: Journal Article
• Authors: Dyckhoff, Florian; Schlagintweit, Jonas F.; Bernd, Marco A.; Jakob, Christian H. G.; Schlachta, Tim P.; Hofmann, Benjamin J.; Reich, Robert M.; Kühn, Fritz E.
• Is Part Of: Catalysis science & technology. Volume 11:Issue 3(2021)
• Page Start: 795
• Page End: 799
• Publication Date: 2021-01-19
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/d0cy02433c
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : Elucidation of different decomposition pathways of a highly active tetradentate iron–NHC epoxidation catalyst reveals direct carbene oxidation to be the decisive cause of catalyst degradation. Abstract : Pivotal degradation pathways of the most active non-heme iron epoxidation catalyst to date are investigated in detail. In-depth HR-ESI-MS and NMR spectroscopy decomposition studies and comparative catalytic experiments exclude the generally accepted literature paths of μ2 -oxo bridged Fe III –O–Fe III dimer formation and methylene bridge oxidation. Instead, the Fe–NHC bond has been identified as the "weak spot". It is shown that direct oxidation of one of the carbenes (ImCO) results in its de-coordination and induces protonation of the other NHC moieties, thus completely deactivating the catalyst. Evidence for protonation prior to carbene oxidation has not been found in this study.