Pd(ii)–NHC coordination-driven formation of water-soluble catalytically active single chain nanoparticles

Abstract

A well-defined linear statistical copolymer precursor, made of styrene, grafted poly(ethylene oxide) and benzimidazolium chloride units serving as N-heterocyclic carbene (NHC) ligand precursors, is designed by random RAFT copolymerization. Intramolecular coordination forming Pd(II)–NHC₂ crosslinks yields single chain nanoparticles (SCNPs). The formation of SCNPs is achieved by the insertion of Pd(OAc)₂ into diluted solution, which is monitored by combined analyses, including NMR, SEC, DLS and TEM. When used for the Suzuki coupling in water, the catalytic activity of these Pd(II)–NHC₂-containing SCNPs is greatly improved relative to Pd(OAc)₂ as a benchmark molecular catalyst. When compared to a molecular catalyst of Pd–NHC₂-type, i.e. with a structure similar to that of the SCNP-supported catalytic units, the conversion to a reaction product is again higher, owing to a beneficial SCNP effect, although an increase in catalytic efficiency is not spectacular.