Formal Cu(III) Species Featuring Dangling Hypochlorite

In nature, halogenation of organic compounds is performed by two different types of enzymes: halogenases and haloperoxidases. One type halogenates the substrate's C-H bond through metal-hypochlorite intermediates (i.e., Fe^III-OCl and V^V-OCl), while the other utilizes HOCl hydrogen-bonded within the enzyme channels. Inspired by the vital role of these enzymes, we attempted to characterize a formal Cu(III) complex with dangling hypochlorite (2), supported by a C₂ symmetric pseudopeptide ligand. 2 was characterized using UV/vis absorption, EPR, XAS, and resonance Raman spectroscopies. Resonance Raman spectroscopic data indicate that the OCl^- ion does not coordinate to the copper center. Furthermore, we employed computational analysis to test our experimental hypothesis, which suggests that (L^●+)Cu(II)/formal Cu(III) with dangling hypochlorite hydrogen bonded to the -NH₂ groups of the ligand is the energetically favored ground state structure. The species reported here is unique, as it represents the distinctive example where hypochlorite is bound to the secondary coordination sphere rather than directly coordinating with the metal center. 2 can perform hydrogen atom abstraction reactions on 4-X-2,6-ditert-butyl phenol (X = H, Me, OMe, ^tBu) derivatives.