Characterization and Reactivity of a Tetrahedral Copper(II) Alkylperoxido Complex

A tetrahedral Cu-II alkylperoxido complex [Cu-II(TMG(3)tach)(OOCm)](+) (1(OOCm)) (TMG(3)tach={2,2 ',2 ''-[(1s,3s,5s)-cyclohexane-1,3,5-triyl]tris-(1,1,3,3-tetramethyl guanidine)}, OOCm=cumyl peroxide) is prepared and characterized by UV/Vis, cold-spray ionization mass spectroscopy (CSI-MS), resonance Raman, and EPR spectroscopic methods. Product analysis of the self-decomposition reaction of 1(OOCm) in acetonitrile (MeCN) indicates that the reaction involves O-O bond homolytic cleavage of the peroxide moiety with concomitant C-H bond activation of the solvent molecule. When an external substrate such as 1,4-cyclohexadiene (CHD) is added, the O-O bond homolysis leads to C-H activation of the substrate. Furthermore, the reaction of 1(OOCm) with 2,6-di-tert-butylphenol derivatives produces the corresponding phenoxyl radical species (ArO.) together with a Cu-I complex through a concerted proton-electron transfer (CPET) mechanism. Details of the reaction mechanisms are explored by DFT calculations.