Pd-complex driven formation of single-chain nanoparticles

We report the facile synthesis of well-defined palladium(II) cross-linked single-chain nanoparticles (Pd-SCNPs) using the ‘repeating unit approach’. The linear precursor polymer (Mn ≈ 10 200 g mol−1, Đ ≈ 1.17) was synthesized via nitroxide mediated statistical copolymerization of styrene and 4-(chloromethyl)styrene (CMS) followed by a post-polymerization modification of the resulting copolymer to covalently attach the triarylphosphine ligand moieties. The ligand content along the lateral polymer chain was 12%. Intramolecular crosslinking was performed in diluted solution with a suitable precursor complex (Pd[1,5-cyclooctadiene]Cl2) to afford the well-defined Pd-SCNPs, which feature a hydrodynamic diameter of Dh = 5.4 nm. The palladium(II) containing single-chain nanoparticles were characterized in-depth using 1H NMR spectroscopy, 31P{1H} NMR spectroscopy, dynamic light scattering (DLS), size exclusion chromatography (SEC), 1H spin–spin relaxation time (T2) analysis, X-ray photoelectron spectroscopy (XPS), and log-normal distribution (LND) simulations. Finally, the applicability of the Pd-SCNPs as catalyst in the Sonogashira coupling was exemplified.