SYNTHESIS AND STRUCTURE OF RB3PDH3 AND RB3PDH5

The ternary palladium hydrides Rb3PdH3 and Rb3PdH3 were synthesized by the reaction of rubidium hydride with palladium sponge in a pure hydrogen atmosphere. The experimental conditions show that higher oxidation states in the transition metal are stabilized with increasing hydrogen pressure. X-ray investigations of powdered samples of Rb3PdH3 led to the determination of the atomic arrangement of the metal atoms (space group I4/mmm), whereas the complete structure of Rb3PdH5, could be determined by neutron diffraction experiments on the deuterated compound (space group P4/mbm). Both crystal structures can be described as framework arrangements of corner-sharing octahedra made of rubidium ions. In this cation arrangement there are isolated hydride ions and also linear [PdH22-] dumbbells (in Rb3PdH3) or planar [PdH42-] groups (in Rb3PdH5). Movements of the [PdHz2-] groups lead to a high temperature modifications of Rb3PdH3.