Observation of a Cu(II)(2) (μ-1,2-peroxo)/Cu(III)(2) (μ-oxo)(2) equilibrium and its implications for copper-dioxygen reactivity.
Synthesis of small-molecule Cu2 O2 adducts has provided insight into the related biological systems and their reactivity patterns including the interconversion of the Cu(II) 2 (μ-η(2) :η(2) -peroxo) and Cu(III) 2 (μ-oxo)2 isomers. In this study, absorption spectroscopy, kinetics, and resonance Raman data show that the oxygenated product of [(BQPA)Cu(I) ](+) initially yields an "end-on peroxo" species, that subsequently converts to the thermodynamically more stable "bis-μ-oxo" isomer (Keq =3.2 at -90 °C). Calibration of density functional theory calculations to these experimental data suggest that the electrophilic reactivity previously ascribed to end-on peroxo species is in fact a result of an accessible bis-μ-oxo isomer, an electrophilic Cu2 O2 isomer in contrast to the nucleophilic reactivity of binuclear Cu(II) end-on peroxo species. This study is the first report of the interconversion of an end-on peroxo to bis-μ-oxo species in transition metal-dioxygen chemistry.
Department of Chemistry, Stanford University, Stanford, CA 94305 (USA).
Matthew T
MT
Kieber-Emmons
Jake W
JW
Ginsbach
Patrick K
PK
Wick
Heather R
HR
Lucas
Matthew E
ME
Helton
Baldo
B
Lucchese
Masatatsu
M
Suzuki
Andreas D
AD
Zuberbühler
Kenneth D
KD
Karlin
Edward I
EI
Solomon
D003300:Copper / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
D003300:Copper; D010100:Oxygen
Raman spectroscopy; copper; dioxygen ligands; structure-function relationship; tyrosinase