CO Serves As Its Own Cocatalyst On Gold

Since the unexpected finding more than 20 years ago that gold, an archetypal inert metal, can serve as a carbon monoxide oxidation catalyst, scientists have searched for the basis of the precious metal’s reactivity. Chemists now know that nanosized gold clusters can catalyze various oxidations, esterifications, and epoxidations, and they have uncovered a few of the mechanistic details. A computational study has found that CO can surprisingly provide a cocatalytic assist to gold nanoclusters during oxidation reactions. This self-oxidation mechanism—uncovered by Xiao Cheng Zeng of the University of Nebraska, Lincoln; Yong Pei of Xiangtan University, in China; and coworkers—reveals a new twist to how gold functions as a catalyst (J. Am. Chem. Soc., DOI: 10.1021/ja309460v). The researchers found that when CO is bound to certain triangular Au₃ active sites on gold nanoclusters in the presence of O₂, the CO molecule helps facilitate bond scission in an adjacent OCOO intermediate. The analysis shows that an attack on the intermediate by the Au₃-bound CO neighbor would significantly accelerate the rate of O–O bond breaking, resulting in formation of two CO₂ molecules.