Complex Transition Metal Hydrides

Abstract

Ternary metal hydrides A_xM_yH_z, in which A stands for an electropositive metal and M for a transition metal, can show salt-like or metallic behavior. The former often applies if the atomic arrangement contains complex [M_yH_z]^nx- structure units, i.e. if the transfer of n electrons from the electropositive partner (A) makes up anionic frameworks. Investigations on the systems A/Pt/H and A/Pd/H with A ≜ Na, K, Rb or Cs show that complex transition metal hydrides A_x[M_yH_z] do exist. Their crystal structures are analogous or related to those of corresponding halogenides. In addition to that, however, high temperature phase transitions are initiated through dynamic behavior of hydrogen ligands in the complex groups. Ternary hydrides with light alkali metals and with alkali earth metals show transitions from salt-like to metallic behavior of these complex compounds.

Key Words:

• hydrides
• crystal structures
• neutron diffraction