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.