Correlation Between the Molecular Structure of Metal‐Supporting Ligands and Catalysis in the Oxygenase‐Mimicking Immobilized Metal Complex Catalysts

Immobilized metal complex catalysts based on bis(imidazolyl)methane are synthesized by using mesoporous silica supports. A hydrophobic support, of which the support surface is functionalized by fluoroalkyl and trimethylsilyl groups, leads to the higher activity of the nickel, iron, and copper catalysts toward cyclohexane oxygenation. On the oxidation of cyclohexane with m CPBA by the nickel or iron catalysts, both activity and alcohol selectivity are enhanced as increasing the extent of the support surface modification. On the reaction with H 2 O 2 , the iron catalyst yields cyclohexanol with high selectivity, whereas the copper catalyst mediates sequential oxidation of the formed cyclohexanol to cyclohexanone. Mononuclear iron complex immobilized catalyst with bis(pyridylmethyl)amine‐anchored hydrophobic support is prepared by the reaction of small excess of FeCl 3 with the support. Reaction of large excess of FeCl 3 to the same support yields a mixture of the mononuclear and dinuclear complexes immobilized catalyst. Analyses of the kinetic isotope effect on the cyclohexane oxidation and the product distribution on the cyclohexene oxidation mediated by the iron catalysts with the same hydrophobic support suggest that the mononuclear iron complex with the TPA like ligand gives electrophilic iron‐based oxidant while the bis(imidazolyl)methane scaffold ligand complex provide radical characteristic oxidant.