Silver(II) and Silver(III) Intermediates in Alkene Aziridination with a Dinuclear Silver(I) Nitrene Transfer Catalyst

In recent years, synthetically useful homogeneous catalysis has been developed with silver, including nitrene transfer reactions for carbon–nitrogen bond formation. However, the mechanisms of silver-catalyzed redox reactions are generally still poorly understood, including a near-total lack of data on oxidized intermediates. Here, we present a detailed experimental study on the oxidation of a dinuclear silver­(I) nitrene transfer catalyst with commonly used hypervalent iodine oxidants (PhINSO2Ar), including structurally characterized examples of silver­(II) oxidation products obtained under catalytically relevant conditions. Furthermore, the silver­(I) catalyst is shown to undergo stepwise oxidation to silver­(II) and silver­(III) intermediates; the generation of silver­(III) intermediates has not previously been demonstrated in nitrene transfer catalysis. In contrast to prior mechanistic hypotheses, our data indicates that nitrene transfer occurs from silver­(III) in this reaction system.