Spectroscopic and kinetic studies of the reaction of [CuI(6-PhTPA)]+ with O2

Abstract

Oxygenation of [Cu^I(6-PhTPA)](SbF₆) in acetone at −90 °C produces a short-lived Cu^III₂(µ-O)₂ intermediate that exhibits an oxygen-isotope-sensitive ν_Cu–O mode at 599 cm⁻¹ and an overtone at 1192 cm⁻¹. The formation of this intermediate is very fast and is second-order in copper(I) complex, implying that two copper-containing species interact in the rate-limiting step or in pre-equilibrium steps prior to the rate determining step. The decay of this intermediate was facile even at −90 °C but did not afford any arene hydroxylation product. Interestingly, the effect of introducing a 6-phenyl substituent on the TPA ligand framework differs from that of a 6-methyl substituent, providing access to a bis(µ-oxo)dicopper(III) intermediate in the former and a (µ-1,2-peroxo)dicopper(II) species in the latter.