A Copper(I) Complex with Two Unpaired Electrons, Synthesised by Oxidation of a Copper(II) Complex with Two Redox-Active Ligands

摘要

Two homoleptic copper(II) complexes [Cu(L1)(2)] and [Cu(L2)(2)] with anionic redox-active ligands were synthesised, one with urea azine (L1) and the other with thio-urea azine (L2) ligands. One-electron oxidation of the complexes initiates an unprecedented redox-induced electron transfer process, leading to monocationic copper(I) complexes [Cu(L1)(2)](+) and [Cu(L2)(2)](+) with two oxidised ligands. While [Cu(L1)(2)](+) is best described as a Cu-I complex with two neutral radical ligands that couple antiferromagnetically, [Cu(L2)(2)](+) is a Cu-I complex with two clearly different ligand units in the solid state and with a magnetic susceptibility close to a diamagnetic compound. Further one-electron oxidation of the complex with L1 ligands results in a dication [Cu(L1)(2)](2+), best described as a Cu-I complex with a twofold oxidised, monocationic ligand and a neutral radical ligand. The stability in at least three redox states, the accumulation of spin density at the ligands and the facile ligand-metal electron transfer make these complexes highly attractive for a variety of applications; here the catalytic aerobic oxidation of alcohols to aldehydes is tested.