Electrochemical Synthesis of a Tetradentate Copper N‑Heterocyclic Carbene Calix[4]arene and Its Transmetalation to Palladium: Activity of the Palladium Complex in Suzuki–Miyaura Cross-Coupling

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.