Figure 5. Water electrophilic attack on ferryl HO-FeV=O site: (a) initial complex containing adsorbed water molecule, (b) transition-state complex, and (c) resulting hydroxylated complex.
4. Conclusions
In the present work the cubane cluster OFe4(μ-O)4(OH)5 was used to model the O-O coupling versus hydroxylation of the reactive terminal oxo center on the iron-containing oxyhydroxides by means of DFT with solvent account. The following results are obtained.
The barrier estimations allow one to conclude that the O-O coupling and hydroxylation and are equally probable. From two forms of terminal oxo center the ferryl one is preferred for hydroxylation and is less preferred for O-O coupling. Therefore, the hydroxylation in fact enhances selectivity of the O-O coupling on the oxyl-oxygen centers.