Influence of amines on the size control of in situ synthesized rutheniumnanoparticles in imidazolium ionic liquids

Abstract

Very stable suspensions of small sized (c.a. 1.2 nm) and homogeneously dispersed ruthenium nanoparticles (RuNPs) were obtained by decomposition, under H₂, of (η⁴-1,5-cyclooctadiene)(η⁶-1,3,5-cyclooctatriene)ruthenium(0), [Ru(COD)(COT)], in various imidazolium derived ionic liquids (ILs: [RMIm][NTf₂] (R = C_nH_2n+1 where n = 2; 4; 6; 8; 10) and in the presence of amines as ligands (1-octylamine, 1-hexadecylamine). These nanoparticles were compared to others stabilized either in pure ILs or by the same ligands in THF. NMR experiments (¹³C solution and DOSY) demonstrate that the amines are coordinated to the surface of the RuNPs. These RuNPs were investigated for the hydrogenation of aromatics and have shown a high level of recyclability (up to 10 cycles) with neither loss of activity nor significant agglomeration.