Electronic properties and reactivity patterns of high-valent metal-oxo species of Mn, Fe, Co, and Ni

Density functional theory (DFT) calculations were performed for a series of significant terminal high-valent metal-oxo complexes, where the metals are Mn, Fe, Co, and Ni, to reveal their electronic property and reactivity patterns toward the inert C-H bond activation. We found that as the metal center changes from Mn to Ni, the bond strength of metal-oxo decreases while the oxyl character of the oxygen increases, which suggests an increase in the hydrogen-abstraction reactivity. This prediction was further strengthened by theoretical reactivity studies, that is, the reactivities of these four metal-oxo species toward inert C-H bond followed an order of MnO ≈ FeO ≪ CoO < NiO. At the orbital level, it was found that three different electron transfer mechanisms were active among these four species. Thus, this study would provide an explanation and intuitive clues for chemists to understand the nature of the high-valent late transition metal-oxo species.