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

Ultra‐small Pd nanoparticles (UNPs) represent a distinctive type of nanomaterial making them very attractive for a range of applications. Herein, chiral sugar‐substituted N‐heterocyclic carbenes (NHCs) with various lengths of alkyl chain (sugar‐NHCs‐nCnH2n+1) were first used to prepare water‐soluble Pd@NHCs‐sugar UNPs via an efficient ligand‐exchange strategy, which can be handled under air and are stable over 10 months. The Pd@NHCs‐sugar UNPs were highly monodisperse, with tunable core diameters from 1.7 to 2.1 nm, and an effect of the particle size on the N‐substituted aliphatic chains was observed. To investigate the accessibility of the surface, the Pd@NHCs‐sugar UNPs were studied as catalysts for C–C coupling reaction in eco‐friendly ethanol aqueous solution without any precipitation of metallic Pd. The presence of the longest aliphatic group in the Pd@NHCs‐sugar UNPs imparts to them the highest catalyst activity (turnover number and turnover frequency up to 196 000 and 3 920 000 h−1).