Catalytic oxidation properties of an acid-resistant cross-bridged cyclen Fe(ii) complex. Influence of the rigid donor backbone and protonation on the reactivity

The catalytic properties of an iron complex bearing a pentadentate cross-bridged ligand backbone are reported. With H2O2 as an oxidant, it displays moderate conversions in epoxidation and alkane hydroxylation and satisfactory ones in aromatic hydroxylation. Upon addition of an acid to the reaction medium, a significant enhancement in aromatic and alkene oxidation is observed. Spectroscopic analyses showed that accumulation of the expected Fe-III(OOH) intermediate is limited under these conditions, unless an acid is added to the mixture. This is ascribed to the inertness induced by the cross-bridged ligand backbone, which is partly reduced under acidic conditions.

Automated summary

The catalytic properties of an iron complex with a pentadentate cross-bridged ligand backbone were investigated. It exhibited moderate conversions in epoxidation and alkane hydroxylation with H2O2 as the oxidant, and satisfactory conversions in aromatic hydroxylation. However, the addition of acid to the reaction medium significantly enhanced the oxidation of aromatics and alkenes. Spectroscopic analysis revealed that the accumulation of the expected Fe-III(OOH) intermediate was limited under these conditions, unless an acid was present, which was attributed to the inertness induced by the cross-bridged ligand backbone that was partly reduced under acidic conditions.