Partially oxidized gold nanoparticles: A catalytic base-free system for the aerobic homocoupling of alkynes

• Gold nanoparticles catalyze the aerobic homocoupling of alkynes without added base.
• Basic O atoms generated by O2 dissociation assist alkyne deprotonation forming H2O.
• Cationic gold sites directly coordinated to O atoms favor the CC bond forming step.
• DFT and kinetic studies show that O2 dissociation is the rate determining step.
• Different aromatic and aliphatic alkynes are coupled in good yields.

The mechanism of alkyne homocoupling over gold nanoparticles and clusters, isolated and supported on CeO2, has been theoretically investigated by means of periodic DFT calculations. The theoretical study indicates that O2 dissociation on gold generates basic O atoms able to abstract the proton of the alkyne, and cationic Auδ+ and Au+ species that decrease the activation barrier for the CC bond forming step. Kinetic results show that the base-free homocoupling of alkynes is effectively catalyzed by gold nanoparticles supported on different solids, and confirm the theoretical prediction that the dissociation of oxygen on the gold nanoparticle is the controlling step of the global reaction.

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