Modular Bidentate Hybrid NHC‐Thioether Ligands for the Stabilization of Palladium Nanoparticles in Various Solvents

Abstract

The synthesis of four different bidentate hybrid NHC-thioether ligands is presented. The corresponding palladium nanoparticles are stable in various solvents, depending on the ligand used, and show high chemoselectivity in the hydrogenation of olefins. The solubility of the nanoparticles can be switched multiple times depending on the pH value of the solvent. XPS analysis (which shows a subtle shift in the binding energy) was identified as a convenient tool to establish the binding mode of NHC ligands.

Zwitterionic amidinates as effective ligands for platinum nanoparticle hydrogenation catalysts

“…Recently, this technique has been described as a useful tool to investigate the binding mode of NHC ligands on a metal surface. 28 Thus, we applied XPS to study the coordination of the imidazolium-amidinate ligands in our Pt NPs. The N 1s signals of ICy· ( p -tol) NCN present binding energies (BE) of 401.3 and 397.4 eV [Fig.…”

Chelating N‐Heterocyclic Carbene Ligands Enable Tuning of Electrocatalytic CO2 Reduction to Formate and Carbon Monoxide: Surface Organometallic Chemistry

“…Noting the catalytic organic transformations mediated by heterogeneous palladium, including asymmetric α‐arylations, hydrogenations of olefins,,, and Buchwald–Hartwig aminations, as well as molecular Pd/NHC complexes used for reductive transformations of CO 2 , tripodal tris‐NHCs were prepared by slightly modified literature methods to give the desired benchtop‐stable tripodal tris‐imidazolium bicarbonate salts ([timtmb R (H)][(HCO 3 ) 3 ], R=Me, i Pr, t Bu; Scheme ). Palladium‐functionalized electrodes (Pd‐timtmb Me , Pd‐timtmb iPr , and Pd‐timtmb tBu ) were then generated by soaking pretreated, thermally annealed palladium foils in 10 m m methanol solutions of [timtmb R (H)][(HCO 3 ) 3 ] for 12 hours to generate the free tridentate carbenes, timtmb R , in situ and washing with methanol to remove excess uncoordinated ligands.…”

Water‐Soluble N‐Heterocyclic Carbene‐Protected Gold Nanoparticles: Size‐Controlled Synthesis, Stability, and Optical Properties

“…With regard to non‐noble metal nanoparticles, Chaudret described the use of sulfonate‐terminated NHC ligands as stabilizing groups for Pt nanoparticles. Ravoo and Glorius have employed water‐soluble NHC‐stabilized metal nanoparticles in catalytic reactions, including the use of bidentate hybrid NHC‐thioether ligands for water‐soluble Pd and Au nanoparticles ,. These systems showed good pH stability; however, as they were destined for catalytic rather than biological applications, stability tests in high ionic strength media or to biologically relevant nucleophiles were not reported.…”