K3MNH5, THE FIRST SALT-LIKE MANGANESE HYD RIDE

K3MnH5 and K3MnD5 were synthesized by the reaction of potassium hydrid e (deuteride) with manganese powder under a hydrogen pressure above 30 00 bar at 875 K. X-ray investigations on powdered samples and elastic neutron diffraction experiments on the deuterated compound at the time -of-flight spectrometer LAD in the temperature range 5 - 600 K led to the complete structure determination. The atomic arrangement is isotyp ic with that of Cs-3[CoCl4]Cl (space group: I4/mcm, Z = 4). The struct ure of K3MnH5 contains isolated [MnH4](2-)-tetrahedra and additional h ydrogen ions which are exclusively coordinated by potassium cations. T he magnetic susceptibilities show Curie-Weiss behaviour. At temperatur es below 50 K there are obviously antiferromagnetic interactions.