Ruthenium nanoparticles, ligands amines

In the case of the particles accommodating amine ligands, a new phenomenon has been evidenced, namely, a dynamic exchange at the NMR timescale between free and coordinated amines. It has been correlated to the TEM and HREM results, which show that, at the early stage of the reaction, the particles display a spherical aspect and a small size (ca. 2-3 nm), and that after a few hours, the particles coalesce into elongated wormlike particles, still constituted of pure, unoxidized hep ruthenium. This NMR observation is particularly interesting since it evidences for these particles a fluxionality similar to that of molecular clusters, which is well documented. The ruthenium nanoparticles contain coordinated mobile surface hydrides, as recently demonstrated by a combination of NMR techniques in solution, gas phase, and in the solid state. ... 

Nanoparticles can be protected by the HDA (hexadecyiamine) ligand to prevent reactions between each other and in order to stabilize them in solution [69]. This stabilization mode presents several advantages such as their behavior as molecular systems, control of the size, size distribution and adjustment of the surface state (Fig. 18.13). Solution C NMR studies evidenced a fast exchange on the NMR time scale between amine ligands free and coordinated to mthenium . In this section, the preparation of HDA-protected ruthenium nanoparticles, the study of the size of the nanoparticles and their characterization will be described. 

In summary, we have over the years investigated a wide range of hgands on the surface of ruthenium nanoparticles. The first conclusion is that the behavior of ligands is similar on these nanoparticles and on molecular complexes. Thus, hydrides and CO coordinate on the surface of these nanoparticles, as well as olefins and methyl groups. The hydrides are always fluxional whereas CO appears only fluxional when the surface of the particles is free. Amines are also fluxional and do... 

---