Synthesis of Water‐Soluble Palladium Nanoparticles Stabilized by Sulfonated N‐Heterocyclic Carbenes

Abstract

A strategy involving the decomposition of palladium(II) organometallic complexes with sulfonated N-heterocyclic carbene ligands leads to the formation of stable and water-soluble Pd nanoparticles. Three different methodologies (thermal decomposition, reduction under CO atmosphere, and reduction with H ) gave particles with different shapes and sizes, ranging from 1.5 to 7 nm. The structures of the organometallic intermediates and organic decomposition products were elucidated by NMR spectroscopy. To check the accessibility of the surface, the nanoparticles were tested as catalysts for the chemoselective hydrogenation of styrene in water. An effect of the particle size on the catalyst activity was observed. The aqueous phase was recycled up to ten times without any precipitation of metallic palladium.

Ultra‐small sugar‐substituted N‐heterocyclic carbene‐protected palladium nanoparticles and catalytic activity

“…Recent research results suggested that hydrophilic Pd@NHCs NPs containing water‐soluble functional groups show efficient catalytic activity in neat water . Incorporation of sugar groups into Pd@NHCs NPs not only introduces chirality but also improves water solubility.…”

“…Water‐soluble Pd NPs can catalyze chemical reactions in aqueous solution . After the successful synthesis and characterization of Pd@NHCs‐sugar UNPs, we were interested in investigating in detail whether these Pd@NHCs‐sugar UNPs systems are catalytically active or whether the aliphatic chains shield the active sites.…”

“…surface modifications and so provided many notable properties, which might make them surpass thiol‐based systems . Just a few examples of NHC‐protected Pd NPs are reported in the literature, and the exchange strategy is an outstanding method because it employs preformed Pd NPs with known shapes and sizes . Richter et al .…”

“…Glorius and co‐workers have reported the preparation of NHC‐protected water‐stable Pd NPs with a size distribution of 4.0–4.9 nm. Jesús and co‐workers have synthesized a series of water‐soluble NHC‐stabilized Pd NPs with different shapes and sizes, ranging from 1.3 to 7.0 nm . Pd‐based nanocatalysts have attracted considerable attention because of their superior catalytic activity in many types of reactions.…”

Gold Nanoparticles Stabilized by Sulfonated‐Imidazolium Salts as Promising Catalyst in Water

“…One way of stabilizing NPs is usually achieved with the use of ligands, which fulfill a triple function: to avoid agglomeration between the particles, to decrease the surface energy and to act as a physical barrier to reduce the diffusion of species to the particle surface. There are at least two types of well‐differentiated interactions between ligands‐NPs; On one side, there are ligands that interact covalently with the surface of the NP : this allows to control the stability of the dispersions of the steric properties of the stabilizer while imparting their characteristics and properties to the modified NPs. On the other side, there are those ligands that have charge, which stabilize the NPs by means of the Coulomb repulsion between the diffuse layers of the NP and the stabilizer …”