Isomorphous crystals of Mn-v(O) and Cr-v(O) corrolazines were characterized by single crystal X-ray diffraction. Reactivity studies with H atom donors and separated PCET reagents show a dramatic difference in H atom abstracting abilities for these two complexes. The implied large difference in driving force is opposite the trend in redox potentials, indicating that basicity is a key factor in determining the striking difference in reactivity for two metal-oxo species in identical ligand environments.