Formally Copper(III)-Alkylperoxo Complexes as Models of Possible Intermediates in Monooxygenase Enzymes

Reaction of [NBu4][(LCuOH)-O-II] with excess ROOH (R = cumyl or tBu) yielded [NBu4] [(LCuOOR)-O-II, the reversible one-electron oxidation of which generated novel species with [CuOQR](2+) cores (formally (CuOOR)-O-III), identified by spectroscopy and theory for the case R = cumyl. This species reacts with weak O-H bonds in TEMPO-H and 4-dimethylaminophenol ((PhOH)-Ph-Nme2), the latter yielding LCu(OPhNme2), which was also prepared independently. With the identification of [CuOOR](2+) complexes, the first precedent for this core in enzymes is provided, with implications for copper monooxygenase mechanisms.