N-Heterocyclic Carbene-Based Iridium and Ruthenium/Iridium Nanoparticles for the Hydrogen Isotope Exchange Reaction through C–H Bond Activations
Résumé
: Suppressing aromatic rings reduction in noble-metal catalyzed H/D exchange reactions still remains a challenge. This drawback may be overcome by finding a synergetic effect in bimetallic nanoparticles (NPs). Herein we report the synthe-sis of bimetallic lipo- and water-soluble Ru/Ir NPs. They were characterized by state-of-the-art techniques such as TEM, HR-TEM, ATR-FTIR, XRD, and solid-state NMR. These NPs were found to be dispersible in both organic and aqueous me-dia thanks to the stabilization and coordination of adequate N-Heterocyclic Carbene (NHC) ligands to the NP surface. They were tested in the deuteration of 2-phenylpyridine, 2-methyl-naftylamine, 5,6,7,8-tetrahydro-naftylamine, and L-lysine using D2 as isotopic source. Bimetallic NPs showed an unusual selectivity towards the H/D exchange of 2-phenylpyridine, deuterating not only the expected C–H positions close to the N atom, but also remote positions on the heterocycle. Additionally, reduction of the aromatic rings, which is a common undesired side-reaction catalyzed by Ru NPs, was not observed. These outcomes, rationalised by a synergetic effect of both metals, are enhanced when NHC lig-ands are on the surface in comparison to model catalysts stabilized by polyvinylpyrrolidone (PVP). Concerning non-aromatic substrates, CH2-α and CH2-ε positions to the amino acid group of L-lysine were fully deuterated, while moderate deuteration of position was observed as iridium content was increased in the bimetallic system.
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