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Colloidal Ru nanoparticles (NP) display interesting catalytic properties for the hydrogenation of (hetero)arenes as they proceed efficiently in mild reaction conditions. In this work, a series of Ru based materials was used in order to selectively hydrogenate quinaldine and assess the impact of the stabilizing agent on their catalytic performances. Ru nanoparticles stabilized with polyvinylpyrrolidone (PVP) and 1‐adamantanecarboxylic acid (AdCOOH) allowed to obtain 5,6,7,8‐tetrahydroquinaldine with a remarkable selectivity in mild reaction conditions by choosing the suitable solvent. The presence of a carboxylate ligand on the surface of the Ru NP led to an increase in the activity when compared to Ru/PVP catalyst. The stabilizing agent had also an impact on the selectivity, as carboxylate ligand modified catalysts promoted the selectivity towards 1,2,3,4‐tetrahydroquinaldine, with bulky carboxylate displaying the highest ones. [ABSTRACT FROM AUTHOR]

The bottom‐up covalent assembly of metallic nanoparticles (NP) represents one of the innovative tools in nanotechnology to build functional heterostructures, with the resulting assemblies showing superior collective properties over the individual NP for a broad range of applications. The ability to control the dimensionality of the assembly is one of the major challenges in designing and understanding these advanced materials. Here, two new organic linkers were used as building blocks in order to guide the organization of Ru NP into two‐ or three‐dimensional covalent assemblies. The use of a hexa‐adduct functionalized C60 leads to the formation of 3D networks of 2.2 nm Ru NP presenting an interparticle distance of 3.0 nm, and the use of a planar carboxylic acid triphenylene derivative allows the synthesis of 2D networks of 1.9 nm Ru NP with an interparticle distance of 3.1 nm. The Ru NP networks were found to be active catalysts for the selective hydrogenation of phenylacetylene, reaching good selectivity toward styrene. Overall, we demonstrated that catalyst performances are significantly affected by the dimensionality (2D vs. 3D) of the heterostructures, which can be rationalize based on confinement effects. [ABSTRACT FROM AUTHOR]

The C66(COOH)12 hexa-adduct has been successfully used as a building block to construct carboxylate bridged 3D networks with very homogeneous sub-1.8 nm ruthenium nanoparticles. The obtained nanostructures are active in nitrobenzene selective hydrogenation. [ABSTRACT FROM AUTHOR]

Core-shell RuPt (Ru core-Pt shell) and PtRu (Pt core-Ru shell) nanoparticles were prepared by decomposing in a two-step procedure a ruthenium ([Ru(COD)(COT)] (COD = 1,5-cyclooctadiene, COT = 1,3,5-cyclooctatriene)) and a platinum complex ([Pt2(dba)3] (dba = dibenzylideneacetone) or [Pt(CH3)2(COD)]) in the presence of 4-(3-phenylpropyl)pyridine (PPP) as a stabilizer and using different Ru/Pt ratios. The data obtained from a combination of several analyses (TEM, HRTEM, WAXS and IR) indicate that the soobtained nanoparticles present a core-shell structure. The catalytic performances of these bimetallic nanoparticles for the selective hydrogenation of trans-cinnamaldehyde were investigated, which provided interesting results as well as useful information to elucidate their structure and composition. Indeed, the catalytic results evidence that: (1) the combination of both metals led in some cases to a synergistic effect on the selectivity of the reaction, and (2) the structure and the composition affected the selectivity of the reaction. [ABSTRACT FROM AUTHOR]

Ultrasmall FeRu bimetallic nanoparticles were prepared by co-decomposition of two organometallic precursors, {Fe[N(Si(CH3)3)2]2}2 and (η4-1,5-cyclooctadiene)(η6-1,3,5-cyclooctatriene)ruthenium(0) (Ru(COD)(COT)), under dihydrogen at 150 °C in mesitylene. A series of FeRu nanoparticles of sizes of approximately 1.8 nm and incorporating different ratios of iron to ruthenium were synthesized by varying the quantity of the ruthenium complex introduced (Fe/Ru=1:1, 1:0.5, 1:0.2, and 1:0.1). FeRu nanoparticles were characterized by TEM, high-resolution TEM, and wide-angle X-ray scattering analyses. Their surface was studied by hydride titration and IR spectroscopy after CO adsorption and their magnetic properties were analyzed by using a superconducting quantum interference device (SQUID). The FeRu nanoparticles were used as catalysts in the hydrogenation of styrene and 2-butanone. The results indicate that the selectivity of the nanoparticle catalysts can be modulated according to their composition and therefore represent a case study on fine-tuning the reactivity of nanocatalysts and adjusting their selectivity in a given reaction. [ABSTRACT FROM AUTHOR]

The reactivity of two classes of ruthenium nanoparticles (Ru NPs) of small size, either sterically stabilized by a polymer (polyvinylpyrrolidone, PVP) or electronically stabilized by a ligand (bisdiphenylphosphinobutane, dppb) was tested towards standard reactions, namely CO oxidation, CO2 reduction and styrene hydrogenation. The aim of the work was to identify the sites of reactivity on the nanoparticles and to study how the presence of ancillary ligands can influence the course of these catalytic reactions by using NMR and IR spectroscopies. It was found that CO oxidation proceeds at room temperature (RT) on Ru NPs but that the system deactivates rapidly in the absence of ligands because of the formation of RuO2. In the presence of ligands, the reaction involves exclusively the bridging CO groups and no bulk oxidation is observed at RT under catalytic conditions. The reverse reaction, CO2 reduction, is achieved at 120 °C in the presence of H2 and leads to CO, which coordinates exclusively in a bridging mode, hence evidencing the competition between hydrides and CO for coordination on Ru NPs. The effect of ligands localized on the surface is also evidenced in catalytic reactions. Thus, styrene is slowly hydrogenated at RT by the two systems Ru/PVP and Ru/dppb, first into ethylbenzene and then into ethylcyclohexane. Selectively poisoning the nanoparticles with bridging CO groups leads to catalysts that are only able to reduce the vinyl group of styrene whereas a full poisoning with both terminal and bridging CO groups leads to inactive catalysts. These results are interpreted in terms of location of the ligands on the particles surface, and evidence site selectivity for both CO oxidation and arene hydrogenation. [ABSTRACT FROM AUTHOR]

The combination between a sulfonated diphosphine (L) and a cyclodextrin (CD) allowed the preparation of very stable water-soluble ruthenium nanoparticles (RuNPs) that displayed pertinent catalytic performances in hydrogenation of unsaturated substrates with a supramolecular control effect of the cyclodextrin. For comparison purpose, the RuNPs were produced by hydrogenation of the organometallic [Ru(1,5-cyclooctadiene)(1,3,5-cyclooctatriene)] complex under mild conditions (3 bar H2; room temperature) and in the presence of L or a L/CD mixture as stabilizer leading to Ru/L and Ru/L/CD systems, respectively. The so-obtained nanoparticles were fully characterized by complementary techniques. Interestingly, NMR investigations evidenced 1) the strong coordination of the sulfonated diphosphine ligand at the metallic surface and 2) in the presence of cyclodextrin, the formation of an inclusion complex between L and CD that modified the coordination mode of the diphosphine. The investigation of both RuNPs systems in biphasic hydrogenation of unsaturated substrates pointed out relevant differences in terms of reactivity, thus evidencing the influence of the supramolecular interaction at the metallic surface on the catalytic performances of the nanocatalysts. This work took advantage of the supramolecular properties of a cyclodextrin to modulate the surface reactivity of diphosphine-stabilized ruthenium nanoparticles and may open new opportunities in the field of nanocatalysis. [ABSTRACT FROM AUTHOR]

Abstract: The influence of PtRu bimetallic particle size and composition on cinnamaldehyde selective hydrogenation has been investigated for the first time using well-defined catalysts based on carbon nanotubes support. Very high selectivity towards cinnamyl alcohol together with high activity have been obtained provided a high temperature treatment of the catalyst is performed. HRTEM, WAXS and EXAFS analyses permit us to conclude that the remarkable influence of this high temperature treatment on both activity and selectivity arises from different phenomena. First, a particle size and a structural effect have been evidence that permits to increase the selectivity. WAXS and EXAFS point the formation of alloyed PtRu nanoparticles. Second, the heat treatment allows the removal of oxygenated groups from CNT surface. This may increase the cinnamaldehyde adsorption capacity and decrease the activation barrier for diffusion of substrate and product on the CNT surface, thus contributing to an increase in the activity. [Copyright &y& Elsevier]