PREPARATION AND CRYSTAL-STRUCTURE OF THE HEXASELENODIPHOSPHATES(IV) OF ANTIMONY AND BISMUTH

Sb-4(P2Se6)(3), and Bi-4(P2Se6)(3) are synthesized from the elements v ia chemical transport reactions with iodine. The isotypic compounds cr ystallize in the monoclinic space group P2(1)/n (No. 14) with lattice parameters a = 2077.7(4) pm, b = 749.35(5) pm, c = 949.49(8) pm, beta = 91.25 (1)degrees for Sb-4(P2Se6)(3) and a = 2086.9(3) pm, b = 747.45 (6) pm, c = 959.23(6) pm, beta = 91.73(1)degrees for Bi-4(P2Se6)(3), respectively. This new structure type is closely related to the struct ure of Pb2P2S6 showing an ordered cation distribution combined with a reorientation of the ethane like [P2Se6](4-) units. From the interatom ic distances in the coordination spheres a smaller lone pair effect of Bi-III compared to Sb-III may be deduced. For both compounds UV/VIS s pectra and temperature dependence of the electrical resistivity are re ported.