Soluble Platinum Nanoparticles Ligated by Long‐Chain N‐Heterocyclic Carbenes as Catalysts

Martínez‐Prieto, Luis M.; Rakers, Lena; López-Vinasco, Angela M.; Cano, Israel; Coppel, Yannick; Philippot, Karine; Glorius, Frank; Chaudret, Bruno; Leeuwen, Piet W. N. M. van

doi:10.1002/chem.201703189

Cited by 6 publications

(4 citation statements)

References 5 publications

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“…Several PtNPs stabilized by carbenes were prepared and shown to display interesting reactivities. 41,42 When using a 13 C labeled sulfonated NHC, 43 the observation of a 13 C− 195 Pt coupling of 940 Hz demonstrated the coordination of the NHC through the carbene carbon. Furthermore, for 3.8 nm PdNPs stabilized by the same water-soluble NHC, the carbene resonance is found near 600 ppm (very broad) as a result of the presence of a conduction band in the particles.…”

Section: Ancillary Ligandsmentioning

confidence: 99%

Organometallic Ruthenium Nanoparticles: Synthesis, Surface Chemistry, and Insights into Ligand Coordination

Martínez‐Prieto

Chaudret

2018

Acc. Chem. Res.

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Although there has been for the past 20 years great interest in the synthesis and use of metal nanoparticles, little attention has been paid to the complexity of the surface of these species. In particular, the different aspects concerning the ligands present, their location, their mode of binding, and their dynamics have been little studied. Our group has started in the early 1990s an investigation of the surface coordination chemistry of ruthenium and platinum nanoparticles but at that time with a lack of adequate techniques to fulfill our ambition. Over 10 years later, we went back to this problem and could obtain a more precise vision of the surface species. This Account is centered on ruthenium chemistry. This metal has been the most studied in our group, first thanks to the availability of a precursor, Ru(cyclooctadiene)(cyclooctatriene) (Ru(COD)(COT)), which possesses the ability to decompose in very mild conditions without leaving residues on the resulting nanoparticles and second because of the absence of magnetic perturbations (Knight shift, paramagnetism, ferromagnetism, etc.), which has allowed the use of solution and solid state NMR. In this respect, it has been possible to evidence the presence of a high concentration of hydrides on the surface of these particles, to study their dynamics, and to show that since the polarity of the Ru-H bond is similar to that of the C-H bond, a Ru/H NP would behave as a big lipophilic entity. The second point was to characterize the coordination of ancillary ligands. This has been achieved for different ligands, in particular phosphines and carbenes, which made possible the study of the modification of NP reactivity induced by surface ligands. This led to the conclusion that the presence of surface ligands can benefit both the activity of NP catalysts and their selectivity. If it was expected that the selectivity could be modulated, the promoting effect from the presence of ligands on, for example, arene or CO hydrogenation was totally unexpected. Playing with poison atoms (Sn, Fe, etc.) or ligands (CO) may allow us to play with the reactivity of the NPs to make them more selective for selected reactions. Finally, the search for specific ligands for nanoparticles is still in its infancy, but some examples have been found as have specific reactions of nanoparticles. Obviously arene hydrogenation and CO hydrogenation were well-known in heterogeneous catalysis, but we could demonstrate that they can be carried out in very mild conditions on ligand stabilized RuNPs. On the other hand, the enantiospecific C-H activation leading to enantioselective labeling of large organic or biomolecules or the C-C bond cleavage in mild conditions were both unexpected. There is still much work to perform for reaching the degree of control on nanoparticles that is presently achieved in organometallic molecular chemistry, but this work shows that it is possible.

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Section: Ancillary Ligandsmentioning

confidence: 99%

Organometallic Ruthenium Nanoparticles: Synthesis, Surface Chemistry, and Insights into Ligand Coordination

Martínez‐Prieto

Chaudret

2018

Acc. Chem. Res.

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“…To support these results, wide-angle X-ray scattering (WAXS) analyses were conducted on both samples, the colloidal suspension obtained by solubilization of RuCl 3 in water and the chemically reduced and surfactant-stabilized ruthenium nanoparticles (Ru@ HEA16Cl). This technique, widely reported in the literature for NPs of noble metals, 48,49 allows obtaining information on the distribution of metal−metal distances within a homogeneous assembly. Indeed, a well-defined radial distribution function (RDF) corroborates the presence of well-crystallized nanoparticles.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Ruthenium Trichloride Catalyst in Water: Ru Colloids versus Ru Dimer Characterization Investigations

et al. 2019

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An easy-to-prepare ruthenium catalyst obtained from ruthenium(III) trichloride in water demonstrates efficient performances in the oxidation of several cycloalkanes with high selectivity toward the ketone. In this work, several physicochemical techniques were used to demonstrate the real nature of the ruthenium salt still unknown in water and to define the active species for this Csp 3 -H bond functionalization. From transmission electron microscopy analyses corroborated by SAXS analyses, spherical nanoobjects were observed with an average diameter of 1.75 nm, thus being in favor of the formation of reduced species. However, further investigations, based on X-ray scattering and absorption analyses, showed no evidence of the presence of a metallic Ru−Ru bond, proof of zerovalent nanoparticles, but the existence of Ru−O and Ru−Cl bonds, and thus the formation of a water-soluble complex. The EXAFS (extended X-ray absorption fine structure) spectra revealed the presence of an oxygen-bridged diruthenium complex [Ru(OH) x Cl 3−x ] 2 (μ-O) with a high oxidation state in agreement with catalytic results. This study constitutes a significant advance to determine the true nature of the RuCl 3 •3H 2 O salt in water and proves once again the invasive nature of the electron beam in microscopy experiments, routinely used in nanochemistry.

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“…8,9 The improved stability of NHC-based SAMs have led to their utilization in a wide range of applications, from catalysis to biosensing and surface patterning. [9][10][11] A significant advantage of NHCs over other surface ligands (i.e. thiols and silanes) is their wide chemical tunability.…”

Section: Introductionmentioning

confidence: 99%

Strong Metal–Adsorbate Interactions Increase the Reactivity and Decrease the Orientational Order of OH-Functionalized N-Heterocyclic Carbene Monolayers

et al. 2019

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Fundamental understanding of the correlation between the structure and reactivity of chemicallyaddressable N-Heterocyclic Carbene molecules (NHCs) is essential for the design of functional NHC-based self-assembled monolayers (SAMs). In this work we identified the ways by which the deposition of chemically-addressable OH-NHCs on Au (111) or Pt (111) surfaces modified the anchoring geometry and chemical reactivity of surface-anchored NHCs. The properties of surface-anchored NHCs were probed by conducting X-ray Photoelectron Spectroscopy (XPS) and polarized Near-edge X-ray Absorption Fine Structures (NEXAFS) measurements. While no preferred orientation was identified for OH-NHCs on Pt (111), the anchored molecules adopted a preferred flat-lying position on Au (111). Dehydrogenation and aromatization of the imidazoline ring along with partial hydroxyl oxidation were detected in OH-NHCs that were anchored on Au (111). The dehydrogenation and aromatization reactions were facilitated, along with partial decomposition, for OH-NHCs that were anchored on Pt (111). The spectroscopic results reveal that stronger metal-adsorbate interactions increase the reactivity of surface-anchored OH-NHCs while decreasing their molecular orientational order. Scheme 2. Schematic illustration of the anchoring geometry of OH-functionalized NHCs on Pt(111) and Au(111) surfaces, as deduced based on polarized NEXAFS measurements.

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Soluble Platinum Nanoparticles Ligated by Long‐Chain N‐Heterocyclic Carbenes as Catalysts

Cited by 6 publications

References 5 publications

Organometallic Ruthenium Nanoparticles: Synthesis, Surface Chemistry, and Insights into Ligand Coordination

Organometallic Ruthenium Nanoparticles: Synthesis, Surface Chemistry, and Insights into Ligand Coordination

Ruthenium Trichloride Catalyst in Water: Ru Colloids versus Ru Dimer Characterization Investigations

Strong Metal–Adsorbate Interactions Increase the Reactivity and Decrease the Orientational Order of OH-Functionalized N-Heterocyclic Carbene Monolayers

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