Iron complexes with nitrogen bidentate ligands as green catalysts for alcohol oxidation

The iron(II) complexes [Fe(N-N)3 ](OTf)2 (N-N = 2,2? - bipyridine, 1,10-phenanthroline and substituted derivatives) were employed as catalyst precursors for the oxidation of primary and secondary alcohols, including glycerol. The single-crystal structure of [Fe(bipy)3](OTf)2 was determined by X-ray crystallography. The catalytic reactions were performed using either H2O2 or tert-butilhydroperoxide (TBHP) as oxidating agent, in mild experimental conditions: with all catalysts employed, secondary alcohols were oxidized to the corresponding ketones with up to 100% yields, whereas other substrates gave lower conversions. Indications on the nature of the catalytically active species, which is probably formed via dissociation of a nitrogen ligand from the iron center, were obtained from NMR and ESI-MS spectra.