Reaction of Cu(I) complexes bearing a phenol group in the ligand with O2 Original Research Article

Reactions of dioxygen and Cu(I) complexes of a series of bis[2-(2-pyridyl)ethyl]amine ligands bearing different phenol groups (2H = N,N-bis[2-(2-pyridyl)ethyl]-2-(3-hydroxyphenyl)ethylamine, 3H = N,N-bis[2-(2-pyridyl)ethyl]tyramine, 4H = N,N-bis[2-(2-pyridyl)ethyl]-2-(2-hydroxy-5-methylphenyl)ethylamine) have been investigated to obtain insight into the reactivity of copper–active oxygen complexes toward phenols. Treatment of [CuI(2H)](PF6) and [CuI(3H)](PF6) with O2 resulted in the benzylic ligand hydroxylation in 9 and 14%, respectively, together with formation of polymeric products, while the reaction of [CuI(4H)](PF6) and O2 gave a dinuclear phenolate copper(II) complex, [Cu2II(4–)2]2+, and H2O2. The structure and reactivity of the active oxygen intermediates are discussed.