An electrochemical approach for the preparation of copper(I) N-heterocyclic carbene complexes has been developed to include a diverse range of ligand precursors. Importantly, the method is effective for a ligand precursor that contains several acidic protons and for which traditional methods of carbene formation are not suitable.

A novel N-heterocyclic carbene 1,3-alternate calix[4]arene complex bearing four palladium(II) centers per ligand has been prepared. Electrochemical synthetic methods were used to prepare the corresponding copper(I) complex, followed by transmetalation onto palladium(II). The activity of the palladium complex was probed in the Suzuki–Miyaura cross-coupling reaction. An inverse correlation between palladium concentration and activity was observed, with the results indicating that calix[4]arenes in the cone conformation may reduce the aggregation of palladium(0) nanoclusters, whereas our 1,3-alternate calix[4]arene does not provide any supramolecular stabilizing effect.

Neutral tetrakis(methylimidazole) (1) and the novel cationic tetrakis(methylimidazolium) (2) calixarenes have been prepared and their solid-state and solution behaviour examined. The neutral imidazole forms a mono-zwitterion at elevated temperature, a feature that has been observed both in solution and in the solid-state. The cationic imidazolium exhibits a range of hydrogen bond interactions with anions, with the titration curves upon binding to basic anions suggesting sequential binding to both the upper and lower rims.