The decomposition of the organometallic precursor [Ru(cod)(cot)] (cod = 1,5-cyclooctadiene; cot = 1,3,5-cyclooctatriene) under mild conditions (room temperature, 3 bars H 2 ) and in the presence of optically pure ligands, L*, namely (R)-2-aminobutanol 1, amino(oxazolines) (2, 3), hydroxy(oxazoline) (4) and bis(oxazolines) (5-8), leads to stable ruthenium nanoparticles exhibiting a mean diameter between 1.6-2.5 nm. These nanoparticles can be isolated and redispersed. They display different mean sizes, shapes and dispersions depending on the stabilizer nature. These new colloids (Ru1-Ru18) have been characterized by both solid state and molecular chemistry techniques, including TEM/HRTEM, WAXS, elemental analysis, and IR and NMR spectroscopy. To further characterize the surface state of these particles, their catalytic behaviour has been examined in the reduction of organic prochiral unsaturated substrates. Although the asymmetric induction obtained is modest, it reveals the influence of the asymmetric ligand coordinated at the surface of the particles.

The diazomethane-mediated cyclopropanation of cyclohexenone using Pd(OAc) 2 and different sources of Pd(0) species as precatalysts has been studied. In the presence of an excess of diazomethane, Pd-(OAc) 2 rapidly evolves to the formation of palladium nanoparticles (less than 1 min), which are active as catalysts in the cyclopropanation process. The nature of these particles has been analyzed through transmission electron microscopy showing a size distribution between 6 and 40 nm. These nanoparticles generated in situ are more active than Pd(0) complexes, preformed nanoparticles, and commercial palladium powder. Cyclic voltammetry measurements of the reaction solution after completion show the presence of Pd(0) species. This is the first time that Pd(0) nanoparticles are evidenced in a cyclopropanation reaction. Moreover, the reduction of Pd(OAc) 2 to Pd(0) in the presence of diazomethane has been theoretically studied through density functional calculations. The formation of methyl and allyl acetates as organic byproducts has been predicted by the theoretical calculations, and these species, as well as oligomers derived from them, have been detected by spectrometric and spectroscopic techniques (MS, NMR, and IR).

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