Ruthenium(II) Complexes Containing Lutidine‐Derived Pincer CNC Ligands: Synthesis,Structure, and Catalytic Hydrogenation of CN bonds |
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Authors: | Dr. Martín Hernández‐Juárez Dr. Joaquín López‐Serrano Dr. Patricia Lara Judith P. Morales‐Cerón Dr. Mónica Vaquero Dr. Eleuterio Álvarez Prof. Verónica Salazar Dr. Andrés Suárez |
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Affiliation: | 1. Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Hidalgo, Carretera Pachuca‐Tulacingo Km 4.5, 42184 Mineral de la Reforma, Hidalgo (Mexico);2. Instituto de Investigaciones Químicas (IIQ) and Centro de Innovación en Química Avanzada (ORFEO‐CINQA), CSIC and Universidad de Sevilla, Avda Américo Vespucio 49, 41092 Sevilla (Spain) |
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Abstract: | A series of Ru complexes containing lutidine‐derived pincer CNC ligands have been prepared by transmetalation with the corresponding silver‐carbene derivatives. Characterization of these derivatives shows both mer and fac coordination of the CNC ligands depending on the wingtips of the N‐heterocyclic carbene fragments. In the presence of tBuOK, the Ru‐CNC complexes are active in the hydrogenation of a series of imines. In addition, these complexes catalyze the reversible hydrogenation of phenantridine. Detailed NMR spectroscopic studies have shown the capability of the CNC ligand to be deprotonated and get involved in ligand‐assisted activation of dihydrogen. More interestingly, upon deprotonation, the Ru‐CNC complex 5 e (BF4) is able to add aldimines to the metal–ligand framework to yield an amido complex. Finally, investigation of the mechanism of the hydrogenation of imines has been carried out by means of DFT calculations. The calculated mechanism involves outer‐sphere stepwise hydrogen transfer to the C?N bond assisted either by the pincer ligand or a second coordinated H2 molecule. |
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Keywords: | carbenes homogeneous catalysis hydrogenation ligands ruthenium |
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