Preferential Reduction of 2-Phenylpyridine under D<sub>2</sub>: Palladium Nanoparticles Stabilized by <i>N</i>-Heterocyclic Carbenes Prefer D<sub>2</sub> to H<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41961645.
- Also identified by DOI 10.1021/acs.nanolett.5c04736 and PMC identifier 13107521.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Late-stage hydrogen isotope exchange and dearomatization reactions under D<sub>2</sub> have recently been used for preparing labeled compounds using metal nanoparticle catalysts. In the case of dearomatization, lower rates are usually observed under D<sub>2</sub> compared to H<sub>2</sub> as a result of a kinetic isotope effect. Here, we report the synthesis of NHC-stabilized PdNPs, their characterization, and their use for the reduction of 2-phenylpyridine to 2-phenylpiperidine or 2-phenylpiperidine-<i>d</i><sub>6</sub>, which reveals an unexpected preference for D<sub>2</sub> over H<sub>2</sub>. This effect is observed using NPs stabilized by polyvinylpyrrolidone (Pd@PVP) but is more pronounced in the presence of NHC ligands (Pd@NHC). DFT calculations reveal that the phenomenon arises from a higher surface concentration of deuterides relative to hydrides in both systems, which is enhanced by the electronic influence of NHC ligands. This study provides the first report and mechanistic insight into an unusual isotopic effect in NP-catalyzed deuteration, highlighting the pivotal role of ligand-NP interactions.