Catalytic Performance of Fe(II)-Scorpionate Complexes towards Cyclohexane Oxidation in Organic, Ionic Liquid and/or Supercritical CO2 Media: A Comparative Study

The catalytic activity of the iron(II) C-scorpionate complexes [FeCl2{HC(pz)(3)}] 1 (pz = pyrazol-1-yl) and [FeCl2{HOCH2C(pz)(3)}] 2, and of their precursor FeCl2 center dot 2H(2)O(3), towards cyclohexane oxidation with tert-butyl hydroperoxide was evaluated and compared in different media: acetonitrile, ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate, [bmim][FAP]), supercritical carbon dioxide (scCO(2)), and scCO(2)/[bmim][X] (X = PF6 or FAP) mixtures. The use of such alternative solvents led to efficient and selective protocols for the oxidation of cyclohexane. Moreover, tuning the alcohol/ketone selectivity was possible by choosing the suitable solvent.