Beschreibung:
<jats:title>Abstract</jats:title><jats:p>In metal‐mediated O<jats:sub>2</jats:sub> activation, nickel(II) compounds hardly play a role, but recently it has been shown that enzymes can use nickel(II) for O<jats:sub>2</jats:sub> activation. Now a low‐coordinate Lewis acidic nickel(II) complex has been synthesized that reacts with O<jats:sub>2</jats:sub> to give a nickel(II) organoperoxide, as proposed for the enzymatic system. Its formation was studied further by UV/Vis absorption spectroscopy, leading to the observation of a short‐lived intermediate that proved to be reactive in both oxygen atom transfer and hydrogen abstraction reactions, while the peroxide efficiently transfers O atoms. Both for the enzyme and for the functional model, the key to O<jats:sub>2</jats:sub> activation is proposed to represent a concomitant electron shift from the substrate/co‐ligand.</jats:p>