Water and Air Stable Copper(I) Complexes of Tetracationic Catenane Ligands for Oxidative C–C Cross-Coupling

Aqueous soluble and stable Cu(I) molecular catalysts featuring a catenane ligand composed of two mechanically interlocked, cationic macrocycles are reported. The mechanical bond in the catenane ligand not only fine-tunes the coordination sphere and kinetically stabilizes the Cu(I) against air oxidation and disproportionation, but also prevents the dissociation of the otherwise electrostatically repulsive cationic macrocycles which are essential for the good water solubility and sustained reactivity of the catalyst. These catenane Cu(I) complexes are active catalysts for the oxidative C–C coupling of indoles and tetrahydroisoquinolines in water with a good substrate scope. The successful use of the catenane ligands in exploiting Cu(I) for oxidative catalysis under aqueous conditions using H2O2 as a green oxidant thus highlights the many unexplored potential of mechanical bonding as a molecular design element in developing new transition metal catalysts.