Mn2MnO4
Mn2MnO4 is not a standard or widely reported oxide of manganese. In established manganese–oxygen chemistry, common stoichiometries include MnO, MnO2, Mn2O3, Mn3O4, and Mn2O7. The notation Mn2MnO4 would correspond to a formula with two manganese atoms and four oxide ions, giving an average manganese oxidation state of +4. However, Mn2MnO4 is not recognized as a discrete, stable phase in conventional phase diagrams or mineral databases, and there is no well-defined crystal structure, synthesis route, or property data specific to a compound uniquely designated Mn2MnO4.
Several interpretations can be considered. It may reflect a misnotation or typographical error for Mn3O4 (manganese(II,III)
Because Mn2MnO4 is not a standard or well-characterized compound, any use of this formula should be verified