Cu(i)–O2 oxidation reactions in a fluorinated all-O-donor ligand environment

Abstract

Investigation of Cu–O₂ oxidation reactivity is important in biological and anthropogenic chemistry. Zeolites are one of the most promising Cu/O based oxidation catalysts for development of industrial-scale CH₄ to CH₃OH conversion. Their oxidation mechanisms are not well understood, however, highlighting the importance of the investigation of molecular Cu(I)–O₂ reactivity with O-donor complexes. Herein, we give an overview of the synthesis, structural properties, and O₂ reactivity of three different series of O-donor fluorinated Cu(I) alkoxides: K[Cu(OR)₂], [(Ph₃P)Cu(μ-OR)₂Cu(PPh₃)], and K[(R₃P)Cu(pin^F)], in which OR = fluorinated monodentate alkoxide ligands and pin^F = perfluoropinacolate. This breadth allowed for the exploration of the influence of the denticity of the ligand, coordination number, the presence of phosphine, and K⋯F/O interactions on their O₂ reactivity. K⋯F/O interactions were required to activate O₂ in the monodentate-ligand-only family, whereas these connections did not affect O₂ activation in the bidentate complexes, potentially due to the presence of phosphine. Both families formed trisanionic, trinuclear cores of the form {Cu₃(μ₃-O)₂}³⁻. Intramolecular and intermolecular substrate oxidation were also explored and found to be influenced by the fluorinated ligand. Namely, {Cu₃(μ₃-O)₂}³⁻ from K[Cu(OR)₂] could perform both monooxygenase reactivity and oxidase catalysis, whereas those from K[(R₃P)Cu(pin^F)] could only perform oxidase catalysis.