The phenol ortho-oxygenation by mononuclear copper(I) complexes requires a dinuclear mu-eta2:eta2-peroxodicopper(II) complex rather than mononuclear CuO2 species”

The mononuclear complex [Cu(L)]+ performs the orthooxygenation
of an exogeneous phenol through the formation
of a dinuclear m-h2+h2-peroxodicopper(II) intermediate,
which is so far the only type of copper–dioxygen complex
that mediates the tyrosinase monophenolase reaction