In situ formed Co clusters in selective oxidation of α-C[sbnd]H bond: Stabilizing effect from reactants.

[Display omitted] • Co nanoclusters were in situ formed in aerobic oxidation of cis -cyclooctene. • Cyclooctene dimer oxide is formed to stabilize the clusters as a surfactant. • Efficient for soluble Co clusters in aerobic oxidation of α-C H of ethylbenzene. • TON of acetophenone yield on Co clusters is 960 times more active than Co salt. • In situ formed Co nanocluster is extended to aerobic oxidation of cyclohexene. Aerobic oxidation of α-C H bond of organic compounds to valuable chemicals is widely investigated in both fundamental research and industry. Due to the good stability of molecular oxygen, severe reaction conditions are generally required. Herein, by in situ synthesis we used molecular oxygen to induce cobalt nanoclusters with the sensitive catalysis in mild selective oxidation. The cobalt containing clusters with an average diameter around 0.9 nm are in situ prepared in the presence of cis -cyclooctene epoxidation and cyclooctene dimer oxide is formed at the interface to stabilize Co clusters with electron donation as an oil-soluble surfactant. The soluble clusters exhibit high activity in selective oxidation of α-C H bond of ethylbenzene into acetophenone and turnover number (TON) reaches about 7 × 104 during 50 h' reaction at 373 K, which is around 960 times more active than the one using CoCl 2 salt as the catalyst, resulting from efficient mass transportation, π bond interaction and oxygen gas activation. Extended work based on this understanding demonstrates that cobalt nanoclusters also effectively catalyze aerobic oxidation of cyclohexene. [ABSTRACT FROM AUTHOR]