Über die Dihydrogenphosphide der Alkalimetalle,MPH2 mit M ≙ Li,Na, K,Rb und Cs

Dihydrogenphosphides of Alkali Metals, MPH₂ (M ? Li, Na, K, Rb, Cs) The dihydrogenphosphides from lithium to cesium were obtained by the reaction of PH₃ with the corresponding solutions of the metals or the metal amides in ammonia. The compounds were examined by X-ray, IR-spectroscopic, and thermochemical techniques. LiPH₂ is not stable at room temperature, while evolving PH₃ it decomposes to yellow products. NaPH₂ is a stable, white compound; above 393 K it decomposes associated with discolouring. KPH₂ and RbPH₂ exist in the region from 110 K to ～400 K in three crystalline forms. Its high-temperature modification is of the sodium chloride-type structure; a monoclinic deformation occurs with decreasing temperature. DSC-measurements revealed a further low temperature form. CsPH₂ crystallizes in the CsCl-type structure between 110 K and ～400 K.