Knight Shift in 13C NMR Resonances Confirms the Coordination of N‐Heterocyclic Carbene Ligands to Water‐Soluble Palladium Nanoparticles. (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. Volume 129:Number 3(2017)
• Page Start: 883
• Page End: 887
• Publication Date: 2016-12-09
• Subjects: Festkörper-NMR-Spektroskopie -- Metallnanopartikel -- N-Heterocyclische Carbene -- Oberflächencharakterisierung -- Palladium; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201610251
• Languages: English
• ISSNs: 0044-8249

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 : Die Koordination N‐heterocyclischer Carben(NHC)‐Liganden an die Oberfläche von Palladium‐Nanopartikeln (PdNPs) kann durch die Beobachtung einer Knight‐Verschiebung (KS) in der 13 C‐Resonanz des carbenischen Kohlenstoffs eindeutig nachgewiesen werden. Der Effekt tritt nur bei Partikeln jenseits einer kritischen Größe von etwa 2 nm auf.