Hidden radical reactivity of the [FeO]2+ group in the H-abstraction from methane: DFT and CASPT2 supported mechanism by the example of model iron (hydro)oxide species

Reactivity of the [FeO]2+ group in the abstraction of hydrogen from methane is determined by metastable oxyl state FeIII O causing the negative spin polarization of the methyl moiety as was shown by quantum-chemical means with the use of model iron hydroxide species FeO(OH)2, Fe2O(OH)5, and Fe4O5(OH)3 as an example. The energy of the gap between the ground-state ferryl configuration FeIV O and the oxyl state correlates with the energy barrier of the H-abstraction from methane.