Mechanism of Oxidative Activation of Fluorinated Aromatic Compounds by N‐Bridged Diiron‐Phthalocyanine. What determines the reactivity?

The biodegradation of compounds with C–F bonds is challenging due to the fact that these bonds are stronger than the C–H bond in methane. Herein, we present results on the unprecedented reactivity of a biomimetic model complex that contains an N‐bridged diiron‐phthalocyanine and show it to react with perfluorinated arenes under addition of H2O2 effectively. To get mechanistic insight into this unusual reactivity, detailed density functional theory calculations on the mechanism of C6F6 activation by an iron(IV)‐oxo active species of the N‐bridged diiron phthalocyanine system were performed. Our studies show that the reaction proceeds through a rate‐determining electrophilic C–O addition reaction followed by a 1,2‐fluoride shift to give the ketone product that can further rearrange to the phenol. A thermochemical analysis shows that the weakest C–F bond is the aliphatic C–F bond in the ketone intermediate. We demonstrate that the oxidative defluorination of perfluoroaromatics proceeds via a completely different mechanism compared to that of aromatic C–H hydroxylation by iron(IV)‐oxo intermediates such as cytochrome P450 Compound I.