Significant effect of 5,10,15,20-meso-tetraarylporphyrinatoiron(III) chloride/triflate and acidic/neutral/basic imidazolium ionic liquids in catalytic oxidation of phenols

Abstract The influence of acidic, neutral and basic ionic liquids and their binary mixture with dichloromethane on the reactivity of iron(III)porphyrins was investigated during oxidation of phenols with hydrogen peroxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III) chloride and 5,10,15,20-tetraarylporphyrinatoiron(III) triflate. The generation of different intermediates of iron(III) porphyrin in different ILs was studied through viscosity, density, UV–Vis and 1 H NMR spectroscopy. The heterolytic cleavage efficiency of (TAP)Fe III -OOH and formation of quinone using iron(III)porphyrin (TAP)Fe III Cl with Cl atom as an axial ligand, is influenced by the structure of imidazolium moiety and the counteranion following the order [(CH 2 ) 4 SO 3 HMIm]CF 3 COO > [Hmim]CF 3 COO > [bmim]TFA »» negligible amount in [bmim]CF 3 SO 3 , [Hmim]CF 3 SO 3 , [bmim]BF 4 , [bmim]PF 6 and [bmim]Cl. On the other hand, the heterolytic cleavage efficiency of (TAP)Fe III -OOH with iron(III)porphyrin (TAP)Fe III CF 3 SO 3 with triflate as an axial ligand, was found in the following order [(CH 2 ) 4 SO 3 HMIm]CF 3 SO 3  > [Hmim]CF 3 SO 3  > [(CH 2 ) 4 SO 3 HMIm]CF 3 COO > [Hmim]CF 3 COO > [bmim] CF 3 COO > [bmim]PF 6  ≈ [bmim]BF 4  ≈ [bmim]CF 3 SO 3 , while epoxidation and polymerization were mainly observed in basic and neutral ILs. The reactive intermediates formed by the reaction of monooxygen donors with (TAP)Fe III Cl varied with ILs, as (TAP) +∙ Fe IV  = O intermediate was dominated in acidic ILs, while (TAP)Fe IV  = O was formed in neutral ILs and (TAP)Fe III -OO – was formed in basic ILs.