Journal of Catalysis 262 (2009) 287–293 Contents lists available at ScienceDirect Journal of Catalysis www.elsevier.com/locate/jcat Palladium nanoparticles supported on polyvinylpyridine: Catalytic activity in Heck-type reactions and XPS structural studies Claudio Evangelisti a , Nicoletta Panziera a , Paolo Pertici b,∗ , Giovanni Vitulli c , Piero Salvadori a,b , Chiara Battocchio d , Giovanni Polzonetti d a Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy b Istituto per la Chimica dei Composti Organometallici, ICCOM-CNR, Sezione di Pisa, via Risorgimento 35, 56126 Pisa, Italy c Advanced Catalysts s.r.l., via Risorgimento 35, 56126 Pisa, Italy d Dipartimento di Fisica, Unità INSTM e CISDiC, Università Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy article info abstract Article history: Received 5 September 2008 Revised 29 December 2008 Accepted 5 January 2009 Available online 3 February 2009 Keywords: Heck reaction Palladium Polyvinylpyridine Metal vapour synthesis X-ray photoelectron spectroscopy Palladium nanoparticles, obtained by metal vapour synthesis (MVS), were deposited on cross-linked polyvinylpyridine. The Pd/PVPy system showed high catalytic activity in the Heck C–C coupling reaction of iodo- and bromo-arenes (iodobenzene, bromobenzene, p-nitrobromobenzene, p-bromoacetophenone, p-(methoxy)bromobenzene) with alkyl acrylates (methyl acrylate, n-butyl acrylate, ethylhexyl trans-3- (4-methoxyphenyl)acrylate) at 100 ◦ C–175 ◦ C working under nitrogen atmosphere as well as in air. The catalyst is stable and the leaching of metal in solution is very low. When reused, the recovered Pd/PVPy maintains the catalytic activity of the pristine material. XPS structural studies performed on the starting catalyst as well as on the recovered one indicate the presence of a interaction between the basic nitrogen of the pyridine present in the polymer and the metal.  2009 Elsevier Inc. All rights reserved. 1. Introduction The palladium-catalyzed coupling of olefins with aryl or vinyl halides, known as the Heck reaction [1], is one of the most im- portant reactions for the formation of C–C bonds in organic syn- thesis, from both the research and industrial points of view [2,3]. It enables the functionalization of sp 2 olefinic carbon atoms with a wide range of aryl and vinyl substrates in a single step under mild conditions. Homogeneous catalytic systems for the Heck reac- tion are generally palladium salts or organo–metallic complexes in the presence of additional ligands, such as phosphines, which pre- vent the formation of catalytically inactive “palladium black” [2,4]. However, the homogeneous systems present difficulties associated with the limited reusability and the removal of homogeneous ma- terials from the reaction mixture [5]. For these reasons, there has recently been increasing interest, from both economic and envi- ronmental points of view, in the development of heterogeneous phosphine-free palladium catalysts which can be recovered from the reaction mixture by simple filtration and subsequently reused. Lately, many solid systems containing supported palladium have been studied with emphasis on the role of the procedure for the preparation of the catalyst and the kind of support (carbon, ze- * Corresponding author. Fax. +39 050 2219260. E-mail address: pertici@dcci.unipi.it (P. Pertici). olite, silica, polymers, etc.) [6]. Unfortunately, in many cases, the supported systems leach palladium under the reaction conditions leading to highly active soluble palladium species. Only a few ex- amples of leach-free heterogeneous palladium systems have been reported; they include palladium salts on zeolites [7], whose be- haviour depends on the catalyst pre-treatment and on the base and solvent used, and palladium nanoparticles deposited on a par- ticular layered double hydroxide [8] or on suitable functionalized zeolites containing primary amino [9] and SH [10] groups. Recently [11] we reported the preparation of palladium cata- lysts by deposition of palladium nanoparticles, prepared by metal vapour synthesis (MVS) [12], on a commercial polyvinylpyridine crosslinked with divinylbenzene (PVPy). This system showed ap- preciable catalytic activity in the Heck reaction using aryl iodide and methyl acrylate as model substrates with an important con- tribution to the overall catalytic activity from supported palladium species. In this context it was emphasized that PVPy, thanks to its affinity with palladium, could be a very interesting catalytic sup- port to obtain leach-free catalysts in Heck reaction. In extension of these interesting preliminary results, we report here an improved method to prepare palladium on PVPy by MVS and a more com- prehensive study of its catalytic activity in the Heck reaction with a wide range of halide substrates. Moreover, in order to better under- stand the nature of the interaction between palladium and PVPy, a study of the structural features performed by X-Ray Photoelec- tron Spectroscopy (XPS) is reported. 0021-9517/$ – see front matter  2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jcat.2009.01.005