Oxidation of ethylbenzene (derivatives) catalyzed by a functionalized ionic liquid combined with cationic (tetrakis(N-methyl-4-pyridinium)porphyrinato) manganese(III) and anionic phosphotungstate

A functionalized ionic liquid (IL) combined with cationic (tetrakis(N-methyl-4-pyridinium)porphyrinato)manganese(III) and anionic phosphotungstate was prepared and applied as the catalyst for ethylbenzene (derivative) oxidations without involvement of the auxiliary axial ligands. A synergetic catalytic effect between the cations and the counteranions in this functionalized IL was observed in terms of activity and stability. Although anionic phosphotungstate ([PW₁₂O₄₀]^3-) showed negligible contribution to the activation of ethylbenzene, it stabilized the manganese porphyrin against oxidative degradation. The in situ UV-Vis analysis of the oxidation of the functionalized IL by PhIO indicated that with the incorporation of [PW₁₂O₄₀]^3- as the counteranion the formation of the μ-oxo Mn^IV porphyrin dimer was completely suppressed, resulting in improved catalytic performance for the corresponding manganese porphyrin.