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

Abstract

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).

Sugar-Based Ionic Liquids: Multifaceted Challenges and Intriguing Potential

“…To this aim, the derivatization of glucose is mainly based on a selective reaction at the anomeric position, which can be made directly on the unprotected sugar 36 or after its peracetylation ( Scheme 19 ). The two main strategies involve: (a) The introduction of halogenated alkyl chain [ 32 , 54 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 ], and (b) the substitution of the hydroxyl group with bromine ( Scheme 19 ) [ 82 , 83 , 84 , 85 , 86 , 87 , 88 ].…”

“…The obtained halo-sugar is used for further derivatizations through S N 2 reactions that directly introduce the final nitrogen-containing cationic group (imidazole or pyridine) through a quaternization reaction, or a functionalized side-chain, which will be further derivatized to obtain the final ionic derivative [ 80 , 82 , 83 , 84 , 85 , 87 , 88 ].…”

“…Other works followed a similar strategy, where per- O -acetyl glycosyl bromide 90a was reacted directly with pyridine [ 83 ], or with imidazole and an alkylating agent to achieve the desired ionic derivative [ 84 , 85 , 86 , 87 ].…”

“…The research group of Zhou also studied the use of glucose-derived ILs as starting materials for the in situ synthesis of ultra-small, water-soluble, and stable Pd nanoparticles. In this example, the metallic species were stabilized by the coordination of N -heterocyclic carbenes resulting from the sugar-containing IL [ 87 ].…”

“… The synthesis of ILs from d -glucose, as reported by Yuan et al [ 83 ] ( A ), and other ILs obtained from per-O-acetyl glycosylbromide 90a ( B ) [ 84 , 85 , 86 , 87 ]. …”