Dioxygen activation at a single copper site: Structure, bonding, and mechanism of formation of 1:1 Cu-O2 adducts

Nermeen W. Aboelella, Sergey V. Kryatov, Benjamin F. Gherman, William W. Brennessel, Victor G. Young, Ritimukta Sarangi, Elena V. Rybak-Akimova, Keith O. Hodgson, Britt Hedman, Edward I. Solomon, Christopher J. Cramer, William B. Tolman

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Abstract

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.

Original languageEnglish (US)
Pages (from-to)16896-16911
Number of pages16
JournalJournal of the American Chemical Society
Volume126
Issue number51
DOIs
StatePublished - Dec 29 2004

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