Lead corrole complexes in solution: Powerful multielectron transfer reagents for redox catalysis Wolfgang Schöfberger a , Florian Lengwin a , Lorenz M. Reith a , Manuela List b , Günther Knör a, ⁎ a Institut für Anorganische Chemie, Johannes Kepler Universität Linz (JKU), Altenbergerstr. 69, A-4040 Linz, Austria b Institut für Chemische Technologie Organischer Stoffe, Johannes Kepler Universität Linz (JKU) Altenbergerstr. 69, A-4040 Linz, Austria abstract article info Article history: Received 13 April 2010 Accepted 30 June 2010 Available online 1 August 2010 Keywords: Lead complexes Metal-oxo species Corroles Charge transfer Electron transfer Photochemistry The first observation of Pb(II)-complexes of corroles and their photoinduced oxidation to the corresponding Pb(IV)-derivatives is reported. These compounds display metal-centered redox chemistry in solution. Their potential for catalytic oxygen atom transfer processes is explored. © 2010 Elsevier B.V. All rights reserved. Metallocorroles are attractive candidates for redox catalysis, since their specific electronic structure is very suitable to stabilize high- valent oxidation states of the coordinated central metals [1]. Compared to the closely related porphyrin-based systems, where the macrocyclic ring tends to be involved as a noninnocent ligand forming π-radical species,[2] this feature determines the extraordi- nary properties of oxygen atom transfer reagents such as manganese (V)-oxo corroles for the epoxidation of alkenes[3] or the O–O bond formation step in artificial photosynthetic water oxidation [4]. Quite unique reactivity patterns have furthermore been observed, when corrole complexes incorporate heavy-atom central ions [5]. In this context, the investigation of tetrapyrrole complexes with high-valent main group metals including Pb(IV), Sb(V) or Bi(V) is of considerable interest due to their intrinsic preference for multielectron reactivity and their potential to form catalytically active oxo species [6]. Especially, the reversible photochemical formation of very strong oxidants such as Pb(IV) compounds carrying hydroxo, oxo or carboxylato groups would be an extremely desirable reaction, since it is well established that high-valent lead compounds are useful reagents for mechanistically demanding substrate conversions such as carbon– carbon-bond formation [7] or electrocatalytic O 2 -evolution [8]. We decided to explore this possibility and studied the metallation of triphenylcorrole[9] H 3 (TPC) 1 with various Pb(II) salts (Scheme 1)[10]. Interaction of an excess of the low-valent main group metal ions with the free base corrole ligand in solution resulted in gradual absorption spectral changes indicating the formation of a sitting-atop complex, which was allowed to further react under an inert atmosphere by stirring the mixture for several hours in the dark [10]. The occurrence of a diagnostic p-type hyper electronic spectrum [11] with band maxima at 310, 415, 450 and 680 nm including a “split” Soret band served as an indicator for the presence of a Pb(II) complex of triphenylcorrole. While at this stage the reaction product was very sensitive to demetallation and all attempts to completely remove excess salts initially failed, the obtained NMR- and high-resolution mass spectral data unambiguously displayed a set of signals and a characteristic isotope pattern consistent with a mononuclear TPC-compound (Fig. 1). Interestingly, the positive ion ESI-signal at m/z=731.01 corre- sponds to the cationic species (TPC)Pb + , which indicates the possibility Inorganic Chemistry Communications 13 (2010) 1187–1190 ⁎ Corresponding author. Tel.: + 43 732 2468 8800; fax: + 43 732 2468 9681. E-mail address: guenther.knoer@jku.at (G. Knör). Scheme 1. 1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.inoche.2010.06.047 Contents lists available at ScienceDirect Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche