N-phosphanylamidine ligands and their catalytic activity in the hydroformylation of 1-octene and styrene Régis Maura a, b , Jennifer Steele a, b , Laure Vendier a, b , Damien Arquier a, b , Stéphanie Bastin a, b , Martine Urrutigoïty a, b, * , Philippe Kalck a, b , Alain Igau a, b, * a CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, F-31077 Toulouse, France b Université de Toulouse, UPS, INPT, LCC, F–31077 Toulouse, France article info Article history: Received 10 October 2010 Accepted 12 October 2010 Available online 23 October 2010 Keywords: Amidines Phosphanes Rhodium Hydroformylation Pyridine X-ray diffraction abstract Pyridine-based N-phosphanylamidine ligands i-Pr 2 NeC(pyr)]NePR 2 (R ¼ Ph (3), i-Pr (4)) were synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Mononuclear rhodium complexes 7 and 8 were obtained in one step from the [RhCl(COD)] 2 dimer and the mono- dentate ligands 1 and 2. Their single-crystal X-ray diffraction studies revealed the structural adaptive behavior of the monodentate N-phosphanylamidine ligands 1 and 2 upon k 1 -P coordination mode in rhodium(I) complexes with the imino nitrogen atom of the amidine function which behaves as a “universal joint”. Compounds 1e4 were evaluated as ligands in the 1-octene and styrene hydro- formylation reactions. The results obtained are encouraging and represent the first report on the use of N-phosphanylamidine ligands of the type R 00 2 NeC(R 0 )]NePR 2 in catalytic reactions. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Hydroformylation is a straightforward synthetic methodology affording aldehydes by creating a CeC bond in only one step from quite inexpensive feedstock. It represents one of the most impor- tant homogeneous catalytic processes applied on an industrial scale [1,2]. A large number of ligands have been developed and applied to this reaction [3e8] and there is continued interest in the development of new mono- and heteroditopic bidentate phos- phane ligands to increase the efficiency and selectivity of this chemical transformation. The straightforward formation of PeN bonds from halophosphanes is a method of choice to prepare easily a large scope of phosphane ligands. This synthetic methodology allows a fine tuning of the steric and electronic properties of the phosphane moiety [9,10]. This high versatility is one of the reasons why, for example, aminophosphane R 2 PeNR 0 2 [10] and phosphor- amidite (RO) 2 PeNR 0 2 [11] ligands are extensively studied for their applications in catalysis. It is noteworthy that very few examples of methylenaminophosphine-type ligands of the general formula R 1 R 2 C]NePR 2 have been tested in catalytic chemical trans- formations [12,13]. “Hybrid” ligands, such as bifunctional P ,N-ligands bearing two chemically different donor atoms, are of particular interest in catalytic reactions since they can reversibly adopt either a k 1 -P or a k 2 -P ,N coordination mode along the catalytic cycle and therefore modify the catalytic properties of the metallic center. Even though the k 1 -P and k 2 -P ,N coordination modes to Rh(I) have been identi- fied with P ,N hybrid ligands, very few experimental data have evidenced the k 2 -P ,N chelating mode under hydroformylation conditions [14]. Nevertheless, the results recorded up to now with these P ,N hybrid ligands highlight the beneficial effect of the presence of the non-coordinated nitrogen function in the catalytic activity [14,15]. On the basis of these considerations, we were interested in developing a class of hybrid P ,N-ligands incorporating PeN bonds. We have a strong experience in the ligand design of monodentate N-phosphanylamidine of the general formula R 00 2 NeC(R 0 )]NePR 2 (R 0 ¼ H, Ph). We have previously reported their reactivity towards Brönsted acids [16], phospheniums [17] and initiated their coordi- nation chemistry with ruthenium metal fragment [18]. Complexes with N-phosphanylamidines as ligands have been reported in the literature before our studies [19,20] but as far as we know, this class of ligands has never been tested in catalysis. In this paper, we report the coordination behavior of monodentate N-phosphanylamidine * Corresponding authors. CNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, F-31077 Toulouse, France. E-mail address: alain.igau@lcc-toulouse.fr (A. Igau). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem 0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2010.10.030 Journal of Organometallic Chemistry 696 (2011) 897e904