Palladium nanoparticle catalysts in ionic liquids: synthesis, characterisation and selective partial hydrogenation of alkynes to Z-alkenes

Abstract

The simple heating (120 C) of Pd(OAc) 2 in 1-butyronitrile-3-methylimidazolium-N-bis(trifluoromethane sulfonyl)imide ((BCN)MI$NTf 2 ) under reduced pressure leads to the formation of stable and small-sized Pd(0)-NPs (diameter: 7.3 AE 2.2 nm). These metal nanoparticles were characterised by means of TEM, HRTEM and XPS analysis techniques. Moreover, the potential for partial hydrogenation of alkynes in multiphase systems was evaluated. The hydrogenation of internal alkynes at 25 C and under 1 bar of hydrogen yields Z-alkenes (up to 98% selectivity). Application of higher hydrogen pressure (4 bar) in these reactions always led to the formation of alkanes without the detection of any alkenes. TOF values were attained up to 1282 h À1 with a good recyclability of the system which does not lose its activity for at least 4 runs.

Recyclable nanoscale copper(i) catalysts in ionic liquid media for selective decarboxylative C–C bond cleavage

“…60 Further detected components were dinitrogen (m/z = 28/14), water (m/z = 18) and other components of air.…”

“…In previous works it has been shown that Pd nanoparticles are obtained by thermal decomposition of Pd(OAc) 2 in IL. 60 Furthermore, studies about the formation of ruthenium and nickel nanoparticles by decomposition of organometallic precursors in ionic liquids showed that (I) the anion plays an important role and (II) the IL itself is capable of inducing the decomposition by reaction with a complex. 9 In these cases minor amounts of IL suffered from decomposition and only traces of volatile compounds were detected in the gaseous phase, indicating decomposition of the IL.…”

“…Similar observations are known for other metal acetates. 60 During Hofmann elimination one would obtain trialkyl phosphine which could then subsequently result in trialkylphosphine oxide and Cu(I). However, the phosphonium cation remains mainly intact, whereas large amounts of CO 2 are formed due to decomposition of the acetate ions which can be detected by mass spectrometry.…”

Fast track to nanomaterials: microwave assisted synthesis in ionic liquid media

“…Surfactants, such as polymers/ dendrimers, [25][26][27][28] ligands and especially ionic liquids sufficiently shield the nanoparticles' surface and effectively prevent agglomeration. [12][13][14][15]19,29,30 Nanoparticles can be synthesised in various ways. There are several top-down and bottom-up methods with their inherent advantages and disadvantages.…”

“…Accordingly, ionic liquids are very popular concerning the synthesis of zero-and one-dimensional nanostructures. [4][5][6][7] Ionic liquids can act as solvents, cosolvents, [8][9][10][11] promoters, 12,13 reducing agents, [12][13][14][15] capping or protective agents and surfactants. 3,16 Despite their low melting points, ionic liquid phases show structural properties of lower order: they consist of polar and nonpolar nanoscale regimes which make them ideal templates for nanoscale synthesis.…”