We report the synthesis of high-valent molybdenum(VI) bis-imido complexes 1-4 with dipyrromethene (DPM) supporting ligands of the general formula (DPMR)Mo(NR')(2)Cl (R, R' = mesityl (Mes) or tertbutyl (Bu-t)). The electrochemical and chemical properties of 1-4 reveal unexpected ligand noninnocence and reactivity. N-15 NMR spectroscopy is used to assess the electronic properties of the imido ligands in the tert-butyl complexes 1 and 3. Complex 1 is inert toward ligand (halide) exchange with bulky phenolates such as KOMes or amides (e.g., KN(SiMe3)(2)), whereas the use of the lithium alkyl LiCH2SiMe3 results in a rare nucleophilic beta-alkylation of the DPM ligand. While the reductions of the complexes occur at molybdenum, the oxidation is centered at the DPM ligand. Quantum-chemical calculations (complete active space self-consistent field, density functional theory) suggest facile (near-infrared) interligand charge transfer to the imido ligand, which might preclude the isolation of the oxidized complex [1](+) in the experiment.