Variable Coordination of Peroxide in a Dinuclear Copper Mono-Oxygenase Model Complex Supported by a Pyridazine-Bridged Ligand

Copper-oxygen intermediates play an important role in nature as active species of many copper-containing enzymes. However, copper-oxygen intermediates have a key function not only in nature, but also in industry, for example as catalysts. Herein a study on a dinuclear copper complex is presented based on the literature known ligand BPMPD. This ligand combines features of the previously investigated systems (octadentate N-donor, like the MO8 system and pyridine donors, like the bdpdz system). Oxygenation of the Cu(I)-complex with O₂ at low temperature leads to the formation of a μ-1,2-peroxo intermediate (Cu₂O₂), which is characterized with UV/Vis-, rRaman- and X-ray absorption spectroscopy (XAS), as well as by cryo-UHR-electrospray ionization mass spectrometry. The Cu₂O₂ species can be reversibly converted into a μ-1,1-hydroperoxo intermediate (Cu₂OOH) by a reaction with lutidinium triflate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), which can be monitored by UV/Vis and XAS. Furthermore, the reactivity of the Cu₂O₂ species toward dihydroanthracene is investigated.