PHOTOCATALYTIC GENERATION OF AN IRON(IV)-OXO COMPOUND. ENHANCED REACTIVITY TOWARDS SULFIDES UNDER LIGHT IRRADIATION

High-valent metal-oxo species are postulated as key oxidants in the catalytic cycle of both heme and non-heme enzymes. In particular, in the field of non-heme iron enzymes high-valent iron-oxo compounds have emerged as key intermediates in several processes. Inspired by biological systems, in the last decade, a wide range of synthetic models of iron(IV)-oxo species have been synthesized by chemical oxidation of the corresponding iron(II) precursors using different oxidants [1]. More recently, Nam and coworkers reported the formation of iron(IV)-oxo species using water as oxygen source. In this case, the iron(II) center was oxidized by 2 electrons using either a strong oxidant (Ce^IV) or a photochemically-generated oxidant in water [2]. The latter strategy is specially appealing as it entails the in situ generation of the oxidant using a sacrificial electron acceptor.

In the present work we report the efficient photocatalytic synthesis of a novel iron(IV)-oxo compound (2) from the corresponding iron(II) complex (1), using catalytic amounts of [Ru^II(bpy)₃]²⁺. As expected, the photocatalytically generated compound 2 reacts with sulfides but most surprisingly there is a remarkable enhancement of the reaction rate (up to two orders of magnitude) when this process is carried out under light irradiation. Moreover, under the experimental conditions compound 2 can be regenerated several times after reaction with sulfides. The complex mechanistic scenario and its implications will be discussed [3].

 

[1] L. Que Jr., Acc. Chem. Res. 2007, 40, 493-500.

[2] a) Y.-M. Lee, S. D. Dhuri, S. C. Sawant, J. Cho, M. Kubo, T. Ogura, S. Fukuzumi, W. Nam, Angew. Chem. Int. Ed. 2009, 48, 1803-1806. b) H. Kotani, T. Suenobu, Y.-M. Lee, W. Nam, S. Fukuzumi, J. Am. Chem. Soc. 2011, 133, 3249-3251.

[3] A. Company, M. González-Béjar, G. Sabeña, L. Gómez, J. Pérez-Prieto, M. Costas, J. Lloret-Fillol, Submitted.