New copper selenites. Part A: K₂Cu₂(SeO₃)₃ and K₂Cu₃(SeO₃)₄

Abstract

Abstract The new compounds K 2 Cu 2 (SeO 3 ) 3 and K 2 Cu 3 (SeO 3 ) 4 were synthesized in the course of low-hydrothermal experiments on natrochalcite-type selenate representatives. The crystal structures were determined by direct methods from single-crystal X-ray diffraction data. K 2 Cu 2 (SeO 3 ) 3 : space group Cmcm , Z = 4, a = 5.312(1) Å, b = 9.858(3) Å, c = 17.595(5) Å, V = 921.4(4) Å 3 , R 1 = 0.023. K 2 Cu 3 (SeO 3 ) 4 : space group P [unk], Z = 1, a = 5.443(1) Å, b = 7.158(2) Å, c = 8.369(3) Å, α = 95.26(2)°, β = 108.58(2)°, γ = 92.17(2)°, V = 307.0(2) Å 3 ; R 1 = 0.035. Both compounds contain sheets built from edge- or cornersharing CuO n polyhedra ( n = 5,6) and trigonal pyramidal selenite groups. These units are linked via the potassium atoms. In K 2 Cu 2 (SeO 3 ) 3 one of the two selenite groups is strongly disordered.