Highly Active and Selective Manganese C=O Bond Hydrogenation Catalysts: The Importance of the Multidentate Ligand, the Ancillary Ligands, and the Oxidation State

The replacement of expensive noble metals by earth‐abundant transition metals is a central topic in catalysis. Herein, we introduce a highly active and selective homogeneous manganese‐based C=O bond hydrogenation catalyst. Our catalyst has a broad substrate scope, it is able to hydrogenate aryl–alky...

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Published in:Angewandte Chemie (International ed.) 2016-09, Vol.55 (39), p.11806-11809
Main Authors: Kallmeier, Fabian, Irrgang, Torsten, Dietel, Thomas, Kempe, Rhett
Format: Article
Language:English
Subjects:
alcohols
Aldehydes
base metals
Catalysis
Catalysts
Coordination compounds
Functional groups
Heavy metals
Hydrogenation
Ketones
Ligands
Manganese
Metals
Noble metals
Oxidation
PNP ligands
Substrates
Transition metals
Valence
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Summary:The replacement of expensive noble metals by earth‐abundant transition metals is a central topic in catalysis. Herein, we introduce a highly active and selective homogeneous manganese‐based C=O bond hydrogenation catalyst. Our catalyst has a broad substrate scope, it is able to hydrogenate aryl–alkyl, diaryl, dialkyl, and cycloalkyl ketones as well as aldehydes. A very good functional group tolerance including the quantitative and selective hydrogenation of a ketone in the presence of a non‐shielded olefin is observed. In Mn hydrogenation catalysis, the combination of the multidentate ligand, the oxidation state of the metal, and the choice of the right ancillary ligand is crucial for high activity. This observation emphasizes an advantage and the importance of homogeneous catalysts in 3d‐metal catalysis. For coordination compounds, fine‐tuning of a complex coordination environment is easily accomplished in comparison to enzyme and/or heterogeneous catalysts. Manganese, if you please: An efficient and selective PN5P‐ligand‐stabilized manganese C=O bond hydrogenation catalyst is able to quantitatively hydrogenate various diaryl, aryl–alkyl, dialkyl, and cycloalkyl ketones with catalyst loadings as low as 0.1 mol %. Additionally, various functional groups are tolerated, including unsubstituted olefins.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201606218