A N3S(thioether)-Ligated CuII-Superoxo with Enhanced Reactivity

Previous efforts to synthesize a cupric superoxide complex possessing a thioether donor have resulted in the formation of an end-on trans-peroxo-dicopper­(II) species, [{(Ligand)­CuII}2(μ-1,2-O22–)]2+. Redesign/modification of previous N3S tetradentate ligands has now allowed for the stabilization of the monomeric, superoxide product possessing a S(thioether) ligation, [(DMAN3S)­CuII(O2•–)]+ (2S), as characterized by UV–vis and resonance Raman spectroscopies. This complex mimics the putative CuII(O2•–) active species of the copper monooxygenase PHM and exhibits enhanced reactivity toward both O–H and C–H substrates in comparison to close analogues [(L)­CuII(O2•–)]+, where L contains only nitrogen donor atoms. Also, comparisons of [(L)­CuII/I]n+ compound reduction potentials (L = various N4 vs DMAN3S ligands) provide evidence that DMAN3S is a weaker donor to copper ion than is found for any N4 ligand-complex.