Adaptive N‑Mesoionic Ligands Anchored to a Triazolylidene for Ruthenium-Mediated (De)Hydrogenation Catalysis

A ruthenium cymene complex bearing a bidentate ligand composed of the N-mesoionic donor N-[1-methylpyridin-4­(1H)-ylidene]­amide and the C-mesoionic donor 1,2,3-triazolylidene was prepared. Spectroscopic analyses including UV–vis, electrochemical, and NMR methods demonstrate that the pyridylideneami...

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Bibliographic Details
Published in:Organometallics 2015-08, Vol.34 (16), p.4076-4084
Main Authors: Donnelly, Kate F, Segarra, Candela, Shao, Li-Xiong, Suen, Rachelle, Müller-Bunz, Helge, Albrecht, Martin
Format: Article
Language:English
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Summary:A ruthenium cymene complex bearing a bidentate ligand composed of the N-mesoionic donor N-[1-methylpyridin-4­(1H)-ylidene]­amide and the C-mesoionic donor 1,2,3-triazolylidene was prepared. Spectroscopic analyses including UV–vis, electrochemical, and NMR methods demonstrate that the pyridylideneamide ligand adapts to its environment and switches, depending on the solvent, between a formally anionic and a neutral donor. A mesoionic pyridinium-amidate structure predominates in polar solvents, whereas a neutral pyridylidene imine structure prevails in apolar solvents. The implications of these solvent-dependent electronic characteristics have been exploited in redox catalysis involving alcohol dehydrogenation and transfer dehydrogenation. The results indicate that the ligand resonance flexibility provides a new approach to enhance catalytic performance.
ISSN:0276-7333
1520-6041
DOI:10.1021/acs.organomet.5b00533