Abstract: | The Layer Structure of Tl[CuAsO4] and Tl[CuPO4] with Layers of Thallium(I) with Stereoactive Lone Pair Single crystals of Tl[CuAsO4] and Tl[CuPO4] were prepared by reaction of oxygen with Tl/Cu/As and Tl/Cu/P alloys, respectively. The new isotypic compounds crystallize in spacegroup C2/c with Z = 8 and lattice constants a = 684.70(7) pm, b = 712.64(5) pm, c = 1822.4(2) pm, β = 92.76(1)° for Tl[CuAsO4] and a = 671.57(8) pm, b = 697.09(6) pm, c = 1789.1(2) pm, β = 93.12(1)° for Tl[CuPO4]. Square planar [CuO4]-units are connected by common corners to form undulated [CuO3]2-chains running along [010]. Interconnection of the chains by arsenate or phosphate groups results in the formation of anionic cuprate-arsenate- and cuprate-phosphate-slabs, respectively. Along [001] these slabs are alternating with double layers of thallium(I) ions in which the stereochemical activity of the Tl+ lone pair is apparent from an hemispheric coordination of thallium by oxygen. The structure is related to that of the orthorhombic form of KCuPO4. |