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Tuning the Stability of Surface Intermediates Using Adsorbed Oxygen: Acetate on Au(111)

Selective oxidative reactions promoted by gold depend critically on controlling the coverage and stability of adsorbed intermediates, as well as promoting specific bond activations of those intermediates. We demonstrate that acetate, a common intermediate in the oxidation of olefins, aldehydes, and...

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Published in:The journal of physical chemistry letters 2014-04, Vol.5 (7), p.1126-1130
Main Authors: Cremer, Till, Siler, Cassandra G. F, Rodríguez-Reyes, Juan Carlos F, Friend, Cynthia M, Madix, Robert J
Format: Article
Language:English
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Summary:Selective oxidative reactions promoted by gold depend critically on controlling the coverage and stability of adsorbed intermediates, as well as promoting specific bond activations of those intermediates. We demonstrate that acetate, a common intermediate in the oxidation of olefins, aldehydes, and alcohols, is destabilized by 7–10 kcal/mol by coadsorbed oxygen relative to its stability on the clean gold surface. The amount of destabilization depends on the oxygen coverage. Peak temperatures of products indicative of oxygen-assisted and clean-surface bond activation differ by up to 130 K. Experiments with d3-acetate show a kinetic isotope effect of 6.9 at 400 K, indicating that the rate-limiting step of the low temperature oxygen-assisted reaction is γ-CH bond breaking. This clearly demonstrates that coadsorbed oxygen activates γ-CH bonds on gold and suggests that an oxygen-assisted activation may also occur for β-CH bonds crucial in oxygen-assisted alcohol coupling on metallic gold catalysts, as predicted by theory.
ISSN:1948-7185
1948-7185
DOI:10.1021/jz500192k