Synthesis and crystal structure of NiHo2(B2O5)2, the first nickel lanthanoid borates with a(infinity)(2)(B2O5)(4-) anion

Single crystals of NiHo2(B2O5)(2) were prepared by a B2O3 Aux-technique in high temperature reactions at 1450 degrees C and investigated by X-ray diffraction. They crystallize in the space group C-2h(5)-P2(1)/c (Nr. 14) with a = 451.0(4); b = 724.8(3); c = 938.8(6) pm; beta = 91.39(1)degrees; Z = 2. The compound is isotypic to CuTb2(B2O5)(2) as well as to the gadolinite structure (FeY2(BeSiO5)(2)) and contains a two dimensional infinite anion with the formula (2)(infinity)(B2O5)(4-). The borate layers consist of four- and eight-membered rings of edge-sharing BO4 tetrahedra. The layers are connected via copper-centered elongated oxygen-octahedra and slightly distorted tetragonal HoO8 antiprisms.