Catalytic oxidation of cyclohexane with hydrogen peroxide and a tetracopper(II) complex in an ionic liquid

The catalytic peroxidative oxidation (with H₂O₂) of cyclohexane in an ionic liquid (IL) using the tetracopper(II) complex [(CuL)₂(μ₄-O,O′,O′′,O′′′-CDC)]₂·2H₂O [HL = 2-(2-pyridylmethyleneamino)benzenesulfonic acid, CDC = cyclohexane-1,4-dicarboxylate] as a catalyst is reported. Significant improvements on the catalytic performance, in terms of product yield (up to 36%), TON (up to 529), reaction time, selectivity towards cyclohexanone and easy recycling (negligible loss in activity after three consecutive runs), are observed using 1-butyl-3-methylimidazolium hexafluorophosphate as the chosen IL instead of a molecular organic solvent including the commonly used acetonitrile. The catalytic behaviors in the IL and in different molecular solvents are discussed.