Role of Heteroatom Substitution on the Stability and Reactivity of Mononuclear Cu(II)-Alkylperoxo Complexes

Abstract

Motivated by copper's essential role in biology and its wide range of applications in catalytic and synthetic chemistry, this work aims to understand the effect of heteroatom substitution on the overall stability and reactivity of biomimetic Cu(II)-alkylperoxo complexes. In particular, we designed a series of tetracoordinated ligand frameworks based on iso-BPMEN = N,N-bis(2-pyridylmethyl)-N’,N’-dimethylethane-1,2-diamine) with varying the primary coordination sphere using different donor atoms (N, O, or S) bound to Cu(II). The copper(II) complexes bearing iso-BPMEN and their modified heteroatom-substituted ligands were synthesized and structurally characterized. These novel complexes are manifested as biomimetic models of enzymatic copper(II) complexes that typically bind the metal through some neutral and anionic amino acid side chains. The in situ generated Cu(II)-alkylperoxo intermediates were spectroscopically characterized and evaluated for their stability and reactivity. The stability and reactivity of copper(II)-alkylperoxo intermediates exhibited diverse behaviors depending on the ligand. Interestingly, the reactivity for the S- and O-coordinated Cu(II)-alkylperoxo intermediates exhibited significantly higher (200 − 300 fold ) electrophilic heteroatom oxidation efficiency compared to the N-bound Cu(II)-alkylperoxo species. Computational studies further support a mechanism involving O–O bond homolysis, followed by efficient oxygen atom transfer. These findings suggest that heteroatom substitution plays a crucial role in fine-tuning the oxidation chemistry of copper(II) complexes, enhancing their potential as biomimetic models for copper-based oxidation reactions.