On divorcing isomers, dissecting reactivity, and resolving mechanisms of propane CH and aryl CX (X = halogen) bond activations mediated by a ligated copper(III) oxo complex

The long suspected presence of two isomeric copper complexes (A and B), proportionally dependent on ESI cone voltage, was confirmed by their isolation, separation and characterization in a travelling wave ion mobility spectrometry–mass spectrometer (TWIMS–MS) with modifications to allow for ion/molecule reactions to be performed. Despite their small difference in cross-sectional area (∼1%) the isomers were well resolved, in part due to a strong interaction of isomer B with the N2 buffer gas. The reactivity of each TWIMS-separated isomer was probed: propane reacted with isomer A via CH bond activation and O-atom transfer, while no such reactions were observed for isomer B; the aryl halides PhX (X = F, Cl, Br, I) also reacted solely with A, via either concerted oxidation and halide transfer, or O-atom transfer. DFT calculations reveal that the aryl CX bond activation of PhX by isomer A involves several mechanistic pathways.