Über CuDy₂[B₈O₁₆] und CuHo₂[B₈O₁₆]: Zwei neue „Metaborate“ mit einem _∞ ¹[B₈O₁₆]^8--Anion / On CuDy₂[B₈O₁₆] and CuHo₂[B₈O₁₆] Two New „Metaborates“ with a _∞ ¹[B₈O₁₆]^8-Anion

Abstract

Nearly colourless single crystals of the compounds CuDy2 [B80 i 6] (I) and CuHo2[B80 )6] (II) have been obtained by a B20 3 flux technique. They crystallize in the structure of CuTb2 [B80 )6] (I) or in an orthorhombic variant (II). X-ray investigations on single crystals led to the space group C2h -P2!/c (Nr. 14) with lattice parameters a = 1025,5(10); b = 836,99(10); c = 621,2(8) pm, ß = 90.47(10)°; Z = 2 (I) and D^h -Pbam (Nr. 55) with a = 840,7(2), b = 616,6(2), c = 1022,0(2) pm, Z = 2 (II). The structures contain 1 [B80 16]8_ chains isolated from each other, which include tri-and tetracoordinated boron, T'fie chains consist of alternating twelve and eight-membered rings of boron and oxygen atoms connected by B 0 4 units. Dy,+ and H o 3+ are octacoordinated and Cu2+ is hexacoordinated in elongated octahedra by oxygen. The relation between these two structures is discussed. Einleitung