Published Paper Details:

The catalytic C-H hydroxylation reactions of different alkane substrates are investigated employing three Fe(II) complexes containing TACN-derivatized tetradentate N4 ligands using H2O2 as a co-oxidant. The large normalized C3/C2 bond selectivity in adamantane oxidation, high degrees of stereoretention in the oxidation of cis-1,2-dimethylcyclohexane and the high kinetic isotope effect values for C-H bond activation indicates the involvement of metal-based oxidant in catalytic processes. The active oxidant is proposed to be an (L)FeV(O)(OH) species (L = Me2,MeBzImTACN, Me2,Me2PyzTACN, Me2,MeImTACN) which may exist in two tautomeric forms related by a proton shift between the oxo and hydroxo ligands. Isotope labeling experiments are in agreement with the oxygen atom in the hydroxylated products originating from both water and hydrogen peroxide, and labeling experiments involving oxygen atom transfer to sterically bulky substrates provide indirect information on the steric influence exerted by the three ligands. These studies indicate that the Me2,Me2PyzTACN, exerts a greater steric influence compared to the Me2,MeImTACN and Me2,MeBzImTACN ligands.