Catalytic dioxygen activation by (nitro)(meso-tetrakis(2-n-methylpyridyl)porphyrinato)cobalt(III) cation derivatives electrostatically immobilized in nafion films: an experimental and DFT investigation.

Complexes of the (nitro)(meso-tetrakis(2-N-methylpyridyl)porphyinato)cobalt(III) cation, [LCoTMpyP(2)(NO2)]4+, in which L = water or ethanol have been immobilized through ionic attraction within Nafion films (Naf). These immobilized six-coordinate species, [LCoTMPyP(2)(NO2)/Naf], have been found to catalyze the oxidation of triphenylphosphine in ethanol solution by dioxygen, therefore retaining the capacity to activate dioxygen catalytically without an additional reducing agent as was previously observed in nonaqueous solution for the non-ionic (nitro)cobalt porphyrin analogs. Heating these immobilized six-coordinate species under vacuum conditions results in the formation of the five-coordinate nitro derivatives, [CoTMPyP(2)(NO2)/Naf] at 85 °C and [CoTMPyP(2)/Naf] at 110 °C. The catalytic oxidation of gas-phase cyclohexene with O2 is supported only by the resulting immobilized five-coordinate nitro complex as was previously seen with the corresponding solution-phase catalyst in dichloromethane solution. ...