Organoiron activation combined with electron- and proton transfer: implications in biology, organic synthesis, catalysis and nanosciences Didier Astruc * Nanosciences and Catalysis Group, LCOO, UMR CNRS No. 5802, Universite ´ Bordeaux I, 33405 Talence Cedex, France Received 8 May 2004; accepted 4 June 2004 Available online 30 July 2004 Abstract This Account summarizes the results obtained in our research group on the intra- and intermolecular organoiron activation of sub- strates by combining the coordination of arenes by CpFe +/0 and electron and/or proton transfer. The concepts involved are those of electron and proton reservoirs, activation of O 2 by single electron transfer in solution, mimic and inhibition of the reactivity of super- oxide radical anion, materials synthesis (for instance fullerene anions), electronic communication between two metals connected by a hydrocarbon bridge, activation of arene ligands for multiple functionalization, giant dendrimer synthesis and electron transfer in catalysis (redox and electron-transfer-chain). Ó 2004 Published by Elsevier B.V. Keywords: Iron; Electron transfer; Proton transfer; Superoxide; Arene; Catalysis; Dendrimer; Molecular materials; Batteries; Fullerenes; Molecular electronics 1. Introduction Iron chemistry occupies a central place in bioinorganic chemistry, catalysis and materials science. Its role in inor- ganic chemistry has also been a key one since the end of the XIX century with the finding of iron pentacarbonyl, and especially since the discovery of ferrocene and its p- structure in the middle of the XX century [1–5]. Iron being also the most common and cheapest metal, efficient chem- istry using iron, exemplified very early with the Haber– Bosch and Fischer–Tropsch processes, is likely to find wide-spread use and applications. In the present Account, I wish to briefly illustrate some aspects of our research in the last 25 years on the connection between organoiron chemistry and electron and proton transfer (Scheme 1). I will tentatively indicate how it led to implications in bi- ology, organic synthesis, catalysis and nanosciences. The following Scheme 1 illustrates the basic concepts, simple reactions and key thermodynamic data that have guided our research in organometallic chemistry. 2. Electron-reservoir complexes, electron-transfer and organoiron activation: concepts and relevance to biology, organic synthesis, catalysis and molecular materials 2.1. Syntheses of electron reservoir complexes The key compound in the beginning of our studies was the yellow complex [FeCp(g 6 -C 6 Me 6 )][PF 6 ], 1 þ ½PF  6 , stable in concentrated sulphuric acid, and eas- ily accessible in large quantities from ferrocene and the arene using the useful ligand substitution reaction 0022-328X/$ - see front matter Ó 2004 Published by Elsevier B.V. doi:10.1016/j.jorganchem.2004.06.020 * Tel.: +33-540-00-62-71; fax: +33-540-00-66-46. E-mail address: d.astruc@lcoo.u-bordeaux1.fr. Journal of Organometallic Chemistry 689 (2004) 4332–4344 www.elsevier.com/locate/jorganchem