Knight Shift in 13C NMR Resonances Confirms the Coordination of N‐Heterocyclic Carbene Ligands to Water‐Soluble Palladium Nanoparticles. Issue 3 (9th December 2016)

• Record Type: Journal Article
• Authors: Asensio, Juan M.; Tricard, Simon; Coppel, Yannick; Andrés, Román; Chaudret, Bruno; de Jesús, Ernesto
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 3(2017)
• Page Start: 865
• Page End: 869
• Publication Date: 2016-12-09
• Subjects: metal nanoparticles -- N-heterocyclic carbenes -- palladium -- solid-state NMR spectroscopy -- surface characterization; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201610251
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The coordination of N‐heterocyclic carbene (NHC) ligands to the surface of 3.7 nm palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the 13 C resonance of the carbenic carbon. In order to validate this coordination, PdNPs with sizes ranging from 1.3 to 4.8 nm were prepared by thermal decomposition or reduction with CO of a dimethyl NHC Pd II complex. NMR studies after 13 CO adsorption established that the KS shifts the 13 C resonances of the chemisorbed molecules several hundreds of ppm to high frequencies only when the particle exceeds a critical size of around 2 nm. Finally, the resonance of a carbenic carbon is reported to be Knight‐shifted to 600 ppm for 13 C‐labelled NHCs bound to PdNPs of 3.7 nm. The observation of these very broad KS resonances was facilitated by using Car–Purcell–Meiboom–Gill (CPMG) echo train acquisition NMR experiments. Abstract : On the (K)nightshift : The coordination of N‐heterocyclic carbene (NHC) ligands to the surface of palladium nanoparticles (PdNPs) can be unambiguously established by observation of Knight shift (KS) in the 13 C resonance of the carbenic carbon. The effect is only observed for particles exceeding a critical size of around 2 nm.