Air- and water-tolerant C-H activation is observed in reactions of ((diimine)Pt((sic)(2-)OH)(2)(2+) dimers with allylic and benzylic C-H groups. The reactions proceed in good yields under mild conditions. Mechanistic studies indicate that the active species is the monomeric [(diimine)Pt(OH2)](2+) dicalion. The related palladium species, [(diimine)Pd((sic)(2)-OH](2)(2+), exhibit similar stoichiometric activations and also effect catalytic oxidation of cyclohexene to benzene with molecular oxygen as the terminal oxidant.