Mononuclear iron complexes relevant to nonheme iron oxygenases. Synthesis, characterizations and reactivity of Fe-Oxo and Fe-Peroxo intermediates?

Dalton Transactions Pub Date: 2009-09-08 DOI: 10.1039/B913470K

Abstract

The new ligand L624E (N,N,N′,N′-tetrakis(5-ethyl-2-pyridylmethyl)ethane-1,2-diamine) was designed as a more robust analog of TPEN (N,N,N′,N′-tetrakis(2-pyridylmethyl)ethane-1,2-diamine) for which the ability at stabilizing high valent Fe-Oxo and Fe-(hydro)peroxo has been reported. With respect to the latter, the pyridyl β-substituents in L624E do not modify the Fe coordination chemistry. From the FeII precursor, [FeO]2+ and FeIII-(hydro)peroxo intermediates are prepared using the same synthetic methods as those reported for the TPEN analogs. The spectroscopic characteristics of all L624E-Fe complexes are very similar to their TPEN analog. However, [(L624E)FeO]2+ has a greater lifetime than that of [(TPEN)FeO]2+. This can be explained by a restricted bimolecular autodegradation due to the bulkiness provided by the ethyl substituents. Regarding small organic molecule oxidation, [(L624E)FeO]2+ and [(L624E)FeOOH]2+ exhibit behaviours that seem to be general for the complexes built with ligands of the TPEN family: [FeO]2+ appears to be efficient to epoxidize olefins, whereas [FeOOH]2+ hydroxylates the aromatic ring of anisole with efficacy.

Graphical abstract: Mononuclear iron complexes relevant to nonheme iron oxygenases. Synthesis, characterizations and reactivity of Fe-Oxo and Fe-Peroxo intermediates
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