The manganese(V) imido complex [(TBP(8)Cz)Mn-V(NMes)] (2) was synthesized from the Mn-III complex [(TBP8Cz) MnIII] (1) and thermolysis of mesityl azide. An X-ray structure of 2 reveals a short Mn-N distance [1.595(4)angstrom], consistent with the Mn-N triple bond expected for a manganese(V) imido species. This high-valent species is remarkably inert to one- and two-electron reductive processes such as NR group transfer to alkenes or H-atom abstraction from O-H bonds. Electrochemical studies support this lack of reactivity. In contrast, oxidation of 2 is easily accomplished by treatment with [(4-BrC6H4)(3)N]center dot+SbCl6, giving a d-radical-cation complex.