Synthesis of Au/Pd bimetallic nanoparticles and their application in the Suzuki coupling reaction Mahmoud Nasrollahzadeh a, *, Abbas Azarian b , Mehdi Maham c , Ali Ehsani a a Department of Chemistry, Faculty of Science, University of Qom, Qom 37185-359, Iran b Department of Physics, University of Qom, Qom, Iran c Department of Chemistry, Aliabad Katoul Branch, Islamic Azad University, Aliabad Katoul, Iran 1. Introduction Suzuki coupling reaction which is predominately catalyzed by palladium (Pd) catalysts, is one of the most powerful tool in organic synthesis and has been widely applied to diverse areas such as natural product synthesis, polymers and material science [1,2]. Development of recoverable and recyclable catalysts for industrial applications has become important from both the environmental and economical view points, and has been well- reviewed in the literature [3]. Among various palladium catalysts for the coupling reactions, homogeneous catalysts have been widely investigated, while less expensive heterogeneous catalysts received scanter attention [4]. The problem with homogeneous catalysis is the difficulty to separate the catalyst from the reaction mixture and the impossibility to reuse it in consecutive reactions. There are some recent methods in the literature for Suzuki coupling reactions by heterogeneous catalysts [5–7]. However, each of these earlier methods suffer due to the use of bulky, expensive and commercially unavailable ligands, high boiling solvents, tedious work-ups, low yields and prolonged reaction times. Therefore, the development of mild, highly efficient and environmentally benign method for the ligand-free Suzuki coupling reactions still remains as an active research area. Metal nanoparticles have been used widely in recent years due to their unique electronic, optical, mechanical, magnetic and chemical properties which differ greatly from the bulk substances [8]. Among metal nanoparticles, gold (Au) nanoparticles for catalytic applications in various organic reactions have attracted considerable attention in recent years. These reactions are traditionally carried out with homogeneous transition metal catalysts. Considering Au(I) is isoelectronic with Pd(0), Au nanoparticles may also catalyze the Suzuki coupling reaction of aryl halides with arylboronic acids. Thus, we decided to concen- trate on developing an efficient heterogeneous catalyst that is air and moisture stable and highly active. As part of our ongoing interest in heterogeneous catalysts and coupling reactions [9–17], we now wish to report the synthesis of Au/Pd bimetallic nanoparticles and their application to Suzuki cross-coupling reaction (Scheme 1). In the present study, we report two-steps synthesis of the Au/Pd bimetallic nanoparticles by arc discharge of Au in deionized (DI) water and deposition of palladium via a simple drop-drying process. 2. Experimental 2.1. Instruments and reagents High-purity chemical reagents were purchased from the Merck and Aldrich chemical companies. All materials were of commercial reagent grade. Melting points were determined in open capillaries Journal of Industrial and Engineering Chemistry xxx (2014) xxx–xxx A R T I C L E I N F O Article history: Received 24 January 2014 Accepted 4 April 2014 Available online xxx Keywords: Nanoparticles Suzuki Gold Palladium Ligand-free A B S T R A C T This communication reports on the synthesis and use of Au/Pd bimetallic nanoparticles, as separable catalysts for ligand-free Suzuki coupling reactions. This method has the advantages of high yields, elimination of homogeneous catalysts, green reaction conditions, simple methodology and easy work up. Catalytic efficiency remains unaltered even after several repeated cycles. The catalyst was characterized using the SEM and EDS. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +98 25 32103595; fax: +98 25 32850953. E-mail address: mahmoudnasr81@gmail.com (M. Nasrollahzadeh). G Model JIEC-1995; No. of Pages 3 Please cite this article in press as: M. Nasrollahzadeh, et al., J. Ind. Eng. Chem. (2014), http://dx.doi.org/10.1016/j.jiec.2014.04.006 Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec http://dx.doi.org/10.1016/j.jiec.2014.04.006 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.