Dioxygen Activation at a Single Copper Site: Structure, Bonding, and Mechanism of Formation of 1:1 Cu−O<sub>2</sub> Adducts
作者: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
DOI:10.1021/ja045678j
日期:2004.12.1
To evaluate the fundamental process Of O-2 activation at a single copper site that occurs in biological and catalytic systems, a detailed study Of O-2 binding to Cu(l) complexes of beta-diketiminate ligands L (L-1 = backbone Me; L-2 = 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 (LCuO2)-Cu-2 was acquired, which led to structural parameters in close agreement to theoretical predictions. Significant Cu(Ill)-peroxo character for the complex was corroborated by XAS. On the basis of stopped-flow kinetics data and theoretical calculations for the oxygenation of (LCu)-Cu-1(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 (LCu)-Cu-1(THF) and (b) direct, bimolecular oxygenation of (LCu)-Cu-1(RCN) via an associative process.