From Paracrystalline Ru(CO)(4) 1D Polymer to Nanosized Ruthenium Metal: A Case of Study through Total Scattering Analysis

The highly defective 1D polymer [Ru(CO)(4)] species, in which Ru atoms are arranged in parallel chains well separated by the ligand shell, is here investigated by total scattering Debye function analysis on synchrotron powder diffraction data. A new chain packing model based on the presence of 2D paracrystalline effects in the ab plane is successfully proposed and well accounts for the unusual combination of sharp and very broad diffraction peaks not compatible with conventional size or strain models. Upon thermolysis, the collinear metal arrangement of the parallel [Ru(CO)(4)] bundles in the polymer is not maintained in the Ru particles, whose nanocrystals are not significantly elongated and show a faulted hcp structure with much smaller domains than in the parent organometallic species. These results thus dismiss the appealing hypothesis that, by using a chain-like precursor, highly anisotropically shaped Ru-metal nanorods can be formed upon controlled pyrolysis.