Spectroscopic Characterization of an FeIV Intermediate Generated by Reaction of XO− (X = Cl, Br) with an FeII Complex Bearing a Pentadentate Non-Porphyrinic Ligand − Hydroxylation and Epoxidation Activity
✍ Scribed by Véronique Balland; Marie-France Charlot; Frédéric Banse; Jean-Jacques Girerd; Tony A. Mattioli; Eckhard Bill; Jean-François Bartoli; Pierrette Battioni; Daniel Mansuy
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 182 KB
- Volume
- 2004
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
Mononuclear Fe^IV^ intermediates have been generated in MeOH upon reaction of sodium hypochlorite or hypobromite with a ferrous complex bearing the pentadentate ligands N‐methyl‐N,N′,N′‐tris(2‐pyridylmethyl)ethane‐1,2‐diamine (L~5~^2^) or N‐methyl‐N,N′,N′‐tris(2‐pyridylmethyl)propane‐1,3‐diamine (L~5~^3^). These highly unstable green complexes are characterized by an absorption band at ca. 750 nm. Mössbauer data indicate that the iron center is low spin (S = 1) with an axial electronic structure, allowing identification of the mononuclear Fe^IV^ complexes as [L~5~Fe^IV^O]^2+^ or [L~5~Fe^IV^OCH~3~]^3+^. In acetonitrile/dichloromethane solutions, the L~5~^3^Fe^IV^ system exhibits very selective activities toward hydroxylation of cyclohexane or epoxidation of cyclooctene and cis‐stilbene. Computational studies performed on [L~5~Fe^IV^O]^2+^ and on the model compound [(NH~3~)~5~Fe^IV^O]^2+^ reveal that the ground state possesses two unpaired electrons in the two π* orbitals, as known for O~2~. Electronic spectra computed by time‐dependent DFT exhibit only one band in the visible region that is essentially due to d‐d transitions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)