Multi-site coordination N-phosphanylamidine ligands as stabilizers for the synthesis of ruthenium nanoparticles

The stabilization of ruthenium nanoparticles is achieved by using for the first time multiple donor coordination site-type ligands, the N-phosphanylamidines R ''(2)N-C(R')=N-P(X)R(2). These ligands, in which the donor sites are directly connected to one another, lead to the formation of small ruthenium nanoparticles in the size range 1.7-3.1 nm that display narrow size distributions and a hexagonal close packed crystalline structure of ruthenium bulk. The characterization of these new samples by a combination of techniques gives information on the surface state of the particles such as the coordination mode of the ligand and the presence of hydrides. CO molecules can also coordinate suggesting that the surface of the particles is not saturated. This work confirms the interest of screening novel ligands for the synthesis of metal nanoparticles and more particularly, of studying their coordination to probe metal nanoparticles' surface properties.