Darstellung,Kristallstruktur und Eigenschaften von KLi2As

Preparation, Crystal Structure, and Properties of KLi₂As The novel arsenide KLi₂As has been synthesized either from the elements or from mixtures of the binary components Li₃As and K₃As in sealed Nb ampoules at 823 K and 623 K, respectively. It crystallizes in the space group Pmmn (no. 59) with a = 445.8(9); b = 671.5(11); c = 627.0(12) pm and Z = 2 formula units. The metallic reflecting silvercoloured platelets hydrolize rapidly under wet air. The compound (Pearson code oP8) is isopuntal with BaLi₂Si and an intermediate between the Li₃N and the Na₃As type of structure. Potassium is distorted tetrahedrally coordinated by four As atoms (d(K? As) = 355 and 367 pm), arsenic by four potassium and six lithium atoms (d(As? K) = 355–367 pm; d(As? Li) = 260–265 pm) in form of a sphenocorona. Lithium is threefold coordinated (distorted trigonal planar) by arsenic and this unit is enveloped by a monocapped trigonal prism build by three lithium and four potassium atoms.