NEW TERNARY ALKALI-METAL-TRANSITION-METAL HYDRIDES SYNTHESIZED AT HIGH-PRESSURES - CHARACTERIZATION AND PROPERTIES

Ternary metal hydrides containing both an alkali metal and a transitio n metal can be synthesized by the conversion of a mixture of the alkal i-metal hydride and the transition metal in an atmosphere of hydrogen at temperatures between 500 and 800 K. At low hydrogen reaction pressu res, only hydrides containing transition metals from subgroup eight in low oxidation states are formed. This restriction is removed at high pressures such that it is possible to prepare the following hydrides a t hydrogen reaction pressures between 1500 and 5000 bar: Na<INF>2</INF >PdH<INF>4</INF>,<INF></INF> Li<INF>5</INF>Pt<INF>2</INF>H<INF>9</INF> , A<INF>2</INF>PtH<INF>6</INF> (A corresponds to Na, K, Rb, or Cs), A< INF>3</INF>MnH<INF>5</INF> (A corresponds to K, Rb, or Cs), K<INF>3</I NF>ReH<INF>6</INF>, and A<INF>3</INF>ReH<INF>10</INF> (A corresponds t o K or Rb). Preliminary experiments have shown that this synthesis rou te also facilitates access to corresponding ternary hydrides containin g the early transition metals. The crystal structures of all the hydri des mentioned were determined by a combination of X-ray and neutron-di ffraction experiments on powder samples. The corresponding deuterium c ompounds were employed for the neutron-diffraction experiments. Additi onally, susceptibility measurements were carried out on the paramagnet ic compounds and interpreted, and spin structures were determined.