Properties Of (Mu-Oxo)Di-Iron Complexes And Catalytic Activity Toward Cyclohexane Oxidation

We report herein the synthesis and characterization of two dinuclear mu-oxo iron compounds obtained through the reactions of FeSO(4)center dot 7H(2)O and FeCl(3)center dot 6H(2)O with 1-(bis-pyridin-2-ylmethylamino)-3-chloropropan-2-ol (L5), which resulted in the compounds [(SO(4))(L5)Fe(mu-O)Fe(L5) (SO(4))]center dot 6H(2)O, 1, and [Cl(L5)Fe(mu-O)Fe(L5)Cl]Cl(2)center dot 2H(2)O, 2. The electronic spectra of both compounds show absorption bands only in the UV range. The electrochemical analysis showed that the dinuclear unit is more stable under reduction in compound 1 than in compound 2, while the Mossbauer spectroscopy revealed that the monodentate ligands (sulfate and chloride) have a significant influence on the Mossbauer parameters determined for 1 and 2, particularly on the quadrupole splitting values. Both compounds were studied as catalysts in reactions of cyclohexane oxidation, using H(2)O(2) and t-BuOOH as oxidants, in a substrate: oxidant: catalyst ratio of 1000:1000:1. Cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide, t-butyl cyclohexyl peroxide and adipic acid were formed during the process. The experiments revealed that compound 2 is, in general, more active than compound 1 in promoting cyclohexane oxidation.