Synthesis and single-crystal structure of the pseudo-ternary compounds LiA[N(CN)₂]₂ (A = K or Rb)

Crystals of LiA[N(CN)₂]₂ were obtained from the reaction of LiCl and ACl (A = K or Rb) with Ag[N(CN)₂] in water and subsequent evaporation of the filtered solution at 80 C under normal atmospheric conditions. Crystals of the title compound form thin rectangular plates that are transparent, colorless, and very fragile. Single-crystal structure analyses have shown that both compounds are isotypic and adopt the tetragonal space group I4/mcm (no. 140, Z = 4) with the cell parameters a = 701.53(12) and c = 1413.7(5) pm for LiK[N(CN)₂]₂ and a = 730.34(10) and c = 1414.4(4) pm for LiRb[N(CN)₂]₂. The crystal structure is described and compared to that of the pseudo-binary alkali metal dicyanamides.