On the Way to a Trisanionic {Cu₃O₂} Core for Oxidase Catalysis: Evidence of an Asymmetric Trinuclear Precursor Stabilized by Perfluoropinacolate Ligands

Abstract

Cu^I complexes of the form K[(R₃ P)Cu(pin^F )], in which (pin^F )^2- is the bidentate, oxygen-donating ligand perfluoropinacolate, were synthesized and characterized. Low-temperature oxygenation of the K[(R₃ P)Cu(pin^F )(PR₃ )] species resulted in a trisanionic bis(μ₃ -oxo) trinuclear copper(II,II,III) core characterized by UV/Vis spectroscopy (λ_max [nm] = 330, 535, 630), cryospray-ionization mass spectrometry, and X-band electron paramagnetic resonance spectroscopy (derivative resonance at 3300 G, Δm_s =2 at 1500 G). The kinetic behavior of the trimeric {Cu₃ O₂ } species was quantified by stopped-flow spectroscopy and the associated electronic structures were investigated by DFT calculations. An asymmetric {Cu₃ O₂ } species, ^As T_pinF , which bears a structure similar to multicopper oxidases, forms prior to full formation of the symmetric trinuclear core, ^Sy T_pinF . The trimer catalytically oxidizes para-hydroquinone to benzoquinone (a form of oxidase chemistry).