Amphiphilic ionic liquid stabilizing palladium nanoparticles for highly efficient catalytic hydrogenation

Abstract

The highly water-soluble palladium nanoparticles (NPs) were synthesized by using the amphiphilic poly(ethylene glycol)-functionalized dicationic imidazolium-based ionic liquid (C(12)Im-PEG IL) as a stabilizing agent. The aqueous dispersed palladium NPs in the range of 1.9 ± 0.3 nm were observed by transmission electron microscopy (TEM). The physicochemical properties of C(12)Im-PEG IL in aqueous phase have been characterized by electrical conductivity, surface tension and dynamic light scattering (DLS) measurements. It was demonstrated that the amphiphilic ionic liquid can form micelles above its critical micelle concentration (CMC) in aqueous solution and the micelles played a crucial role in stabilizing the palladium NPs and thus promoted catalytic hydrogenation. Furthermore, the dicationic ionic liquid can also act as a gemini surfactant and generated emulsion between hydrophobic substrates and the catalytic aqueous phase during the reaction. The aqueous dispersed palladium NPs showed efficient activity for the catalytic hydrogenation of various substrates under very mild conditions and the stabilizing Pd(0) nanoparticles (NPs) can be reused at least eight times with complete conservation of activity.

Di‐ and Tricationic Organic Salts: An Overview of Their Properties and Applications

“…Diimidazolium‐based DOSs have also been used as agents for stabilizing palladium nanoparticles. Hou et al reported data on the synthesis of highly water‐soluble palladium nanoparticles through the use of a dicationic PEG‐based IL 28 with chloride anions (Scheme ) 53…”

Solution and thermal behaviour of novel dicationic imidazolium ionic liquids

“…23 In some other cases, the reported catalytic ability is a result of the formation of an organometallic complex. 24,25 Here, we describe the structure-property relationships and thermal behaviour of a series of multi-positive imidazolium ionic liquids paired with multi-negative anions with respect to properties and applications. [26][27][28][29][30] In particular, we thought it could be interesting to study new dicationic ionic liquids functionalised with a basic moiety.…”

Surface-active ionic liquids for palladium-catalysed cross coupling in water: effect of ionic liquid concentration on the catalytically active species

“…For example Zhu et al reported the formation of well-dispersed palladium colloids in amphiphilic imidazolium-based ionic liquids that acted simultaneously as stabilizers for the nanoparticles and as surfactants generating an emulsion for the hydrophobic substrates. 46 Palladium nanoparticles were prepared in aqueous solution via hydrogenation, and are formed independent of the concentration range of the ionic liquid. When assessing the impact of ionic liquid concentration on the catalytic activity, the authors observed a constant increase in turn-over frequency (TOF) that continued distinctly above the CMC of the respective ionic liquid, and only decreases slowly at very high concentrations.…”