Palladium nanoparticles, prepared by the hydrogenation of Pd(dba)₂ in the presence of a tris-imidazolium iodide as stabilizer, act as an efficient catalyst for Heck and copper-free Sonogashira reactions with a range of aryl iodides and bromides at 0.2 mol-% Pd loading. Moreover, we describe a convenient protocol for the fluoride-free Hiyama coupling of vinylsilanes with aryl iodides that involves the use of sodium hydroxide as promoter in a methanol/water mixture. Under the developed conditions, one-pot, double Heck and Hiyama–Heck reactions are successfully achieved.

Catalysis of the oxidative processes by iodoarenes has become a promising direction in synthesis. The mechanism, involving the well-known isolable hypervalent iodine species, is generally limited to aromatic iodides, since the corresponding aliphatic species are normally highly unstable. Nevertheless, in this work catalytic amount of several primary, secondary or tertiary iodoalkanes were found to promotes the α-tosyloxylation of a range of ketones with RSO₃H, including aliphatic sulfonates. The process, was found to proceed through the oxidative breakdown of the iodoalkane to an inorganic catalytic species (likely IO⁻ or IO₂⁻), thus falling within the previously described catalysis using molecular iodine or inorganic iodides. The catalyst eventually becomes deactivated through the precipitation of an iodine overoxidation product, the structure of which was solved ab initio from the powder diffraction data as a hitherto unreported phase of the iodic acid (HIO₃).

Inspired by the proclivity of various palladium sources to form nanoparticles in imidazolium-based ionic liquids, we now report that tris-imidazolium salts bearing hexadecyl chains and a bridging mesitylene moiety are potent stabilizers of palladium nanoparticles efficiently prepared via a Chaudret-type hydrogenation of the bis(dibenzylideneacetone)palladium(0). The palladium nanoparticles have been isolated in pure form and characterized by ¹H nuclear magnetic resonance, transmission electron microscopy, electron diffraction and dynamic light scattering. The new materials proved effective in Suzuki cross-coupling at a loading of 0.2% palladium. Thus, using a tris-imidazolium iodide-palladium material, a series of biaryl products has been prepared starting from aryl bromides and some activated chlorides. The possibility that this catalytic activity might be due to the formation of palladium N-heterocyclic carbenes has been addressed through solid state ¹³C NMR and the synthesis of an imidazolium analogue in which the acidic 2-H was replaced with a methyl group.

A new PEG-tagged material, which was prepared by a threefold copper-catalyzed [3+2] cycloaddition (click chemistry), was found to act as an efficient stabilizer for palladium nanoparticles. The newly formed material proved to be active as a recyclable catalyst in Suzuki coupling; the presence of polyether chains allowed for the catalytic runs to be conducted in aqueous media.