New Example of a Non-Heme Mononuclear Iron(IV) Oxo Complex. Spectroscopic Data and Oxidation Activity

The green complex S = 1 [(TPEN)FeO]²⁺ [TPEN = N,N,N‘,N‘-tetrakis(2-pyridylmethyl)ethane-1,2-diamine] has been obtained by treating the [(TPEN)Fe]²⁺ precursor with meta-chloroperoxybenzoic acid (m-CPBA). This high-valent complex belongs to the emerging family of synthetic models of Fe^IVO intermediates invoked during the catalytic cycle of biological systems. This complex exhibits spectroscopic characteristics that are similar to those of other models reported recently with a similar amine/pyridine environment. Thanks to its relative stability, vibrational data in solution have been obtained by Fourier transform infrared. A comparison of the FeO and Fe¹⁸O wavenumbers reveals that the Fe−oxo vibration is not a pure one. The ability of the green complex to oxidize small organic molecules has been studied. Mixtures of oxygenated products derived from two- or four-electron oxidations are obtained. The reactivity of this [FeO]²⁺ complex is then not straightforward, and different mechanisms may be involved.