Five-coordinate (Nitro)cobalt porphyrins are known to catalytically activate dioxygen to oxidize alkenes. Similar results have now been replicated with a cationic (nitro)cobalt porphyrin (NO₂)CoTMpyP(2) that is immobilized within NafionŽ films.  The oxidation of gas-phase cyclohexene with O₂ (at 85 °C at atmospheric pressure) in the presence of the five-coordinate (nitro)cobalt porphyrins on Nafion results in formation of a mixture of oxidized cyclohexene products including the epoxide, alcohols and ketones. This observation supports the existance of a reactive (peroxynitro)cobalt porphyrin intermediate since the catalysis presumably occurs at isolated cobalt porphyrin centers bound within the polymer film.  Such an intermediate could form from the interaction of O₂ with the known (nitrosyl)cobalt porphyrin that results from O-atom transfer.  Reactions of solution-phase mixtures of triphenylphosphine and cyclohexene with dioxygen in ethanol in the presence of six-coordinate (nitro)(ethanol)cobalt porphyrin on NafionŽ films also result in the oxidation of the cyclohexene as well as the stronger O-atom acceptor triphenylphosphine.  Since cyclohexene is itself not reactive with the six-coordinate (nitro)cobalt porphyrin as triphenylphosphine is, it appears to be oxidized by the more strongly oxidizing peroxynitrite intermediate.  This intermediate would form after triphenylphosphine produces the air-sensitive (nitrosyl)cobalt porphyrin that reacts with O₂ to produce the (peroxynitro)cobalt porphyrin intermediate.