Dioxygen Activation at a Single Copper Site:  Structure, Bonding, and Mechanism of Formation of 1:1 Cu−O2 Adducts

• Published in: Journal of the American Chemical Society 2004-12, Vol.126 (51), p.16896-16911
• Main Authors: Aboelella, Nermeen W, Kryatov, Sergey V, Gherman, Benjamin F, Brennessel, William W, Young, Victor G, Sarangi, Ritimukta, Rybak-Akimova, Elena V, Hodgson, Keith O, Hedman, Britt, Solomon, Edward I, Cramer, Christopher J, Tolman, William B
• Format: Article
• Language: English
• Subjects: Binding Sites; Biological and medical sciences; Copper - chemistry; Crystallography, X-Ray; Fundamental and applied biological sciences. Psychology; Kinetics; Mechanisms. Catalysis. Electron transfer. Models; Molecular biophysics; Organometallic Compounds - chemistry; Oxidation-Reduction; Oxygen - chemistry; Physical chemistry in biology; Spectrometry, X-Ray Emission; Spectrophotometry, Ultraviolet; Thermodynamics
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja045678j

To evaluate the fundamental process of O2 activation at a single copper site that occurs in biological and catalytic systems, a detailed study of O2 binding to Cu(I) complexes of β-diketiminate ligands L (L1 = backbone Me; L2 = backbone tBu) by X-ray crystallography, X-ray absorption spectroscopy (XAS), cryogenic stopped-flow kinetics, and theoretical calculations was performed. Using synchrotron radiation, an X-ray diffraction data set for L2CuO2 was acquired, which led to structural parameters in close agreement to theoretical predictions. Significant Cu(III)−peroxo character for the complex was corroborated by XAS. On the basis of stopped-flow kinetics data and theoretical calculations for the oxygenation of L1Cu(RCN) (R = alkyl, aryl) in THF and THF/RCN mixtures between 193 and 233 K, a dual pathway mechanism is proposed involving (a) rate-determining solvolysis of RCN by THF followed by rapid oxygenation of L1Cu(THF) and (b) direct, bimolecular oxygenation of L1Cu(RCN) via an associative process.