Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst
| Autor: | Sjoerd Harder, Jonathan Eyselein, Christian Knüpfer, Ulrich Zenneck, Christian Färber, Michael Wiesinger, Philipp Stegner |
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| Rok vydání: | 2020 |
| Předmět: |
metal activation
Aldimine Materials science alkaline earth metals Ba‐Metal Catalysis | Very Important Paper barium hydride Conjugated system 010402 general chemistry 01 natural sciences Catalysis Metal chemistry.chemical_compound Polymer chemistry Benzene Research Articles chemistry.chemical_classification Heptane 010405 organic chemistry Hydride General Chemistry Tetraphenylethylene General Medicine hydrogenation catalysis 0104 chemical sciences chemistry visual_art visual_art.visual_art_medium ddc:546 Research Article |
| Zdroj: | Angewandte Chemie (International Ed. in English) |
| ISSN: | 1521-3757 0044-8249 |
| DOI: | 10.1002/ange.202014326 |
| Popis: | Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non‐conjugated) mono‐, di‐ and tri‐substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect. Just a pinch of Ba metal: Efficient hydrogenation of a wide range of substrates is achieved with metallic barium previously activated by metal vapor synthesis. A mechanism in which Ba0 and BaH2 are both essential is discussed. |
| Databáze: | OpenAIRE |
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