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 isot ypic compounds crystallize in spacegroup C2/c with Z = 8 and lattice c onstants a = 684.70(7)pm, b = 712.64(5)pm, c = 1822.4(2)pm, beta = 92. 76(1)degrees for Tl[CuAsO4] and a = 671.57(8)pm, b = 697.09(6) pm, c = 1789.1(2) pm, beta = 93.12(1)degrees for TI[CuPO4]. Square planar [Cu O4]-units are connected by common corners to form undulated (1)(infini ty)[CuO3](2)-chains running along [010]. Interconnection of the chains by arsenate or phosphate groups results in the formation of anionic c uprate-arsenate and cuprate-phosphate-slabs, respectively. Along [001] these slabs are alternating with double layers of thallium(I)) ions i n which the stereochemical activity of the Tl+ lone pair is apparent f rom an hemispheric coordination of thallium by oxygen. The structure i s related to that of the orthorhombic form of KCuPO4.