Formal Valence, Charge Distribution and Chemical Bond in a Compound with a High Oxidation State: KMnO4

KMnO₄ has unusual formal manganese oxidation state Mn⁺⁷ that seems puzzling: the energy of creating such ion (119 eV) is much greater than the energy of chemical bonds (up to ~10 eV). We have used the Wannier functions formalism to analyze the distribution of Mn-$$3d$$ electrons and O-$$2p$$ electrons for empty electronic states in the $${\text{MnO}}_{4}^{ - }$$ complex and have found that, while formally one has $${{d}^{0}}$$ configuration for manganese ion in this compound, in reality only about one-half of the hole density described by these Wannier functions corresponding to this configuration belongs to d-electrons, while the other half is spread over surrounding oxygen atoms. This corresponds much more to Mn⁺⁷ state than to Mn⁺², because the calculated total number of d‑electrons is equal to 5.25. Our analysis has also sown nearly perfect covalent type of chemical bond within the $${\text{MnO}}_{4}^{ - }$$ complex with negligible contribution of the ionic part.