Facile preparation of ruthenium nanoparticles with activity in hydrogenation of aliphatic and aromatic nitriles to amines Carmen Ortiz-Cervantes a , Iliana Iyañez a and Juventino J. García a * The thermal decomposition of [Ru 3 (CO) 12 ] allowed the production of ruthenium nanoparticles (NPs) with a unique activity for this metal in the hydrogenation of aliphatic nitriles, yielding the corresponding tertiary amines (selectivity >80%) and aromatic nitriles to secondary amines and imines at 140  C, employing a moderate hydrogen pressure. The use of several stabilizing agents such as sodium dodecylsulfate and sodium 2-ethylhexanoate allowed the stabilization of ruthenium NPs (Ru-NPs), and further reactivity in the hydrogenation process was assessed. The Ru-NPs were characterized by transmission electron microscopy and exhibited an average size of 2–3 nm. Copyright © 2012 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this paper. Keywords: nitriles; ruthenium nanoparticles; hydrogenation; amines; imines INTRODUCTION The catalytic hydrogenation of nitriles has long been used for the preparation of various amines. [1] Typically, it is performed over metallic catalysts, mainly in homogeneous liquid phase. [2] This method is of high industrial relevance and has been applied to the commercial production of amines like hexamethylenediamine, derived from the hydrogenation of adiponitrile (ADN). [3] Lower alkylamines ranging from 2 to 5 carbon atoms have been used as solvents or reagents in pharmaceutical, agricultural and catalytic applications. [4] The catalytic hydrogenation of nitriles is a good atom economy example and a valuable route to production of amines. [5] In industry, simple alkyl and aryl nitriles are hydroge- nated in the presence of heterogeneous catalysts such as Raney-type nickel and cobalt. [6,7] In a recent report, the complex HInCl 2 was used in the reduction of aromatic and aliphatic nitriles to primary amines. [8] A conventional hydrogenation process leads to a mixture of products that regularly contain secondary and tertiary amines, due to the high reactivity of partially hydrogenated reaction intermediates, i.e. imines or Schiff bases. [9] The employed metal in the catalyst is one of the most important factors in determin- ing the activity and selectivity for the hydrogenation of alkyl- or aryl-nitriles; particularly, the ruthenium-based catalysts [10–12] largely exhibit the highest selectivity to primary amines, while palladium and platinum-based catalysts preferentially yield secondary and tertiary amines. [3,13–15] The use of transition metal nanoparticles (NPs) in catalysis has gained interest since they mimic metal surface activation and heterogeneous catalysis at the nanoscale, showing, in several cases, higher selectivity and efficiency compared to other heterogeneous catalysts. NPs can be envisaged as clusters containing from a few tens to several thousand metal atoms, usually stabilized by ligands, surfactants or polymers protecting their surfaces. [16] As catalysts, these systems can show a great activity due to the potential large surface and their availability to chemically transform substrates. [17] Ru-NPs can be efficiently obtained from [Ru 3 (CO) 12 ] by thermal or photolytic decomposition under argon atmosphere. [18–22] Interestingly, Ru-NPs can also be prepared and stabilized with nitrile-functionalized ionic liquids showing activity towards the hydrogenation of other nitrile-substituted aromatic com- pounds. [23] The use of metal NPs for nitrile hydrogenation has also been documented for silver NPs. In this case, acetonitrile (AN) was hydrogenated to yield the corresponding tertiary amine (triethylamine) along with NH 3 . [24] The use of bimetallic Ni-Ru catalyst supported on mesoporous silica has been assessed in the hydrogenation of AN. Conversion values depend on the Ni/(Ni + Ru) composition of the bimetallic catalysts. The Ru-rich bimetallic catalysts exhibited higher reactivity towards AN hydrogenation to yield ethylamine com- pared with pure Ni. [25] For several years, our group has been interested in the use of metal NPs in applications to catalysis. In a recent report, palladium NPs were successfully used in the desulfurization of dibenzothiophene via cross coupling reactions with Grignard reagents. [26] Herein, we report our findings on the Ru-NPs- catalyzed nitrile hydrogenation of alkyl and aryl nitriles. EXPERIMENTAL All manipulations were performed using a MBraun glovebox (<1 ppm, H 2 O and O 2 ). 100 mL and 300 mL stainless steel Parr W autoclaves were * Correspondence to: J. J. García, Facultad de Química, Universidad Nacional Autónoma de México, México City 04510, México. E-mail: juvent@servidor.unam.mx a C. Ortiz-Cervantes, I. Iyañez, J. J. García Facultad de Química, Universidad Nacional Autónoma de México, México City 04510, México Research Article Received: 2 March 2012, Revised: 9 April 2012, Accepted: 16 April 2012, Published online in Wiley Online Library: 2012 (wileyonlinelibrary.com) DOI: 10.1002/poc.2962 J. Phys. Org. Chem. (2012) Copyright © 2012 John Wiley & Sons, Ltd.