PREPARATION, CRYSTAL-STRUCTURE, AND PROPE RTIES OF KLI2AS

The novel arsenide KLi2As has been synthesized either from the element s or from mixtures of the binary components Li3As and K3As in sealed N b ampoules at 823 K and 623 K, respectively. It crystallizes in the sp ace 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 p latelets hydrolize rapidly under wet air. The compound (Pearson code o P8) is isopuntal with BaLi2Si and an intermediate between the Li3N and the Na3As type of structure. Potassium is distorted tetrahedrally coo rdinated 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) = 26 0-265 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 a toms.