Palladium immobilized on amidoxime- functionalized magnetic Fe 3 O 4 nanoparticles: a highly stable and efficient magnetically recoverable nanocatalyst for sonogashira coupling reaction Hojat Veisi a *, Alireza Sedrpoushan b , Behrooz Maleki c , Malak Hekmati d , Masoud Heidari b and Saba Hemmati a We describe the synthesis of a novel Fe 3 O 4 /amidoxime (AO)/Pd nanocatalyst by grafting of AO groups on Fe 3 O 4 nanoparticles and subsequent deposition of Pd nanoparticles. Prior to grafting of AO, the 2-cyanoethyl-functionalized Fe 3 O 4 nanoparticles prepared through combining 2-cyanoethyltriethoxysilane and Fe 3 O 4 were treated with hydroxylamine. The AO-grafted Fe 3 O 4 nanoparticles were then used as a platform for the deposition of Pd nanoparticles. The catalyst was characterized using Fourier transform infra- red spectroscopy, X-ray diffraction, scanning and transmission electron microscopies, vibrating sample magnetometry, wavelength- and energy-dispersive X-ray spectroscopies and inductively coupled plasma analysis. Fe 3 O 4 /AO/Pd is novel phosphine-free recyclable heterogeneous catalyst for Sonogashira reactions. Interestingly, the novel catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled seven times without any signif- icant loss in activity. Copyright © 2015 John Wiley & Sons, Ltd. Keywords: Fe 3 O 4 /AO/Pd; magnetic nanoparticles; heterogeneous catalyst; Pd nanoparticles; Sonogashira Introduction In the past few decades, much attention has been paid to research dedicated to the development of environmentally compatible pro- cesses. Along with this awareness, industries have started implementing safer practices such as waste prevention using new catalysts. In this regard, the design of environmentally benign, eco- nomical, practical and efficient processes for catalyst separation and reuse has attracted much attention as a central focus area in green chemistry research in the twenty-first century. Supported metal nanoparticles (NPs) are excellent catalysts for a variety of re- actions because of their large surface-to-volume ratio, remarkable efficiency, topological properties, interaction between them and supports, and their heterogenization on various oxide and carbon supports that allow their recovery. [1] In particular, iron oxide mag- netic nanoparticles (MNPs) have received considerable attention because they are biocompatible and can be recovered easily from reaction mixtures using a simple external magnetic field. [2] Conventionally, the fixation of NPs on supports is mostly carried out by the reduction of metal salts in the presence of the support followed by an adequate thermal treatment. [3] Mesoporous sup- ports (MCM-41, SBA) are frequently used as supports for Pd NPs– MNPs. [4a–c] Other supports, such as polymer-coated MNPs, [4d–g] ionic-liquid-modified MNPs [4h] and sulfonated graphene-decorated MNPs, [4i] are also employed for the stabilization of Pd NPs. Phos- phine and amine ligands grafted on MNPs are also common for this purpose. [4j–o] The immobilization methods used to deposit Pd into heteroge- neous solid beds have been studied extensively, and diverse sup- ports such as clay, [5] carbon nanofibres, [6] montmorillonite, [7] magnetic mesoporous silica, [8] zeolites [9] and metal oxides [10] have been investigated. A current challenge in this area is the develop- ment of efficient immobilized systems that can simultaneously fulfil the usual targets of achieving high turnover numbers and facilitate recovery and reuse as well as the need for obtaining Pd-free final products, [11,12] meeting the strict purity specifications for the phar- maceutical industry. [13,14] The Sonogashira cross-coupling of aryl halides with terminal al- kynes has been employed for the synthesis of several compounds bearing internal alkyne moieties, including biologically active mole- cules and functional polymers. [15–17] Toxic and expensive homoge- neous palladium phosphine complexes, which are rarely * Correspondence to: Hojat Veisi, Department of Chemistry, Payame Noor University, Tehran, Iran. E-mail: hojatveisi@yahoo.com a Department of Chemistry, Payame Noor University, Tehran, Iran b Institute of Industrial Chemistry, Iranian Research Organization for Science and Technology, Tehran, Iran c Hakim Sabzevari University, Department of Chemistry, PO Box 397, Sabzevar, Iran d Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Chemistry, Pharmaceutical Sciences Branch, (IAUPS), Tehran, Iran Appl. Organometal. Chem. 2015, 29, 834–839 Copyright © 2015 John Wiley & Sons, Ltd. Full paper Received: 12 August 2015 Revised: 29 August 2015 Accepted: 1 September 2015 Published online in Wiley Online Library: 5 October 2015 (wileyonlinelibrary.com) DOI 10.1002/aoc.3390 834