CuHo2[B2O5]2: Ein unerwarteter Strukturtyp in der Reihe der Kupferlanthanoidborate / CuHo2[B2O5]2: An Unexpected Structure Type in the Series of Copper Lanthanoid Borates

Single crystals of the new compound CuHo2 [B2O5]2 were obtained by using a B2O3 flux technique with CuO and Ho2O3 at 1050 °C. X-ray investigations on single crystals led to the space group P 21/c (Nr. 14) with lattice parameters a = 454.3(2); b = 726.0(4); c = 936.0(5) pm; β = 90.77(1)°; Z = 2. The compound is isotypic to CuTb2[B2O5]2 as well as to the gadolinite structure (FeY2[BeSiO5]2). The structure exhibits layer-like ∞ 2[B2O5]4-, a two-dimensional anion consisting of edge sharing BO4 -tetrahedra, which form four- and eight-membered rings. The layers are connected by elongated CuO6-octahedra and slightly distorted tetragonal LnO8-antiprisms.

AgSr[B7O12]: Das erste wasserfreie quaternäre Silber(I)-Borat mit vierfach koordiniertem Silberion und einem neuartigen Boratanion/ AgSr[B7O12]: The First Anhydrous Quaternary Silver(I)-Borate with Fourfold Coordinated Silver Ion and a New

Single crystals of AgSr[B7O12] were obtained by using a B20 3 flux-technique and Ag2CO3 and SrCO3 as starting materials in a silver ampoule at 800 °C. X-ray investigations on single crystals led to the space group C 2/c with a = 664.2(5); b = 1153.6(3); c = 2198.0(6) pm; β = 92,52(3)°; Z = 8. Ag+ is fourfold coordinated by oxygen atoms and forms distorted AgO4 tetrahedra while Sr2+ has nine nearest neighbours. The compound contains a hitherto unknown two dimensional borate anion [B7O12]3-which contains four trigonal planar BO3 groups and three BO4 tetrahedra per unit.

Ag2Cs[B15O24]: Ein wasserfreies quaternäres Silber(I)-Borat mit einem neuartigen Boratanion mit helixartigem Aufbau / Ag2Cs[B15O24]: An Anhydrous Quaternary Silver(I)-Borate with a New Helical Borate Anion

Single crystals of Ag2Cs[B15O24] were prepared by using a B2O3 flux technique with Ag2CO3 and Cs2CO3 in a closed silver tube at 650 °C. X-Ray investigations led to a new crystal structure in the space group P 21212 (Nr. 18) with lattice parameters a = 1778.7 (4); b = 2219.2 (4); c = 512.2 (1) pm, Z = 4. The silver atoms are part of distorted AgO4 tetrahedra and planar AgO3 units while the caesium atoms are eightfold coordinated by oxygen. The compound contains an as yet unknown borate anion [B15O24] with twelve BO3- and three BO4 units per formula. The BO3 units are connected to eight cords twisted to helices which are combined via BO4 tetrahedra to a three dimensional framework with large tunnels occupied by the cations.