CHEMISTRY AND STRUCTURAL CHEMISTRY OF PHOSPHIDES AND POLYPHOSPHIDES .58. TETRABARIUMTRIPHOSPHIDE, BA4P3 - PREPARATION AND CRYSTAL-STRUCTURE

Ba4P3 is obtained from the elements in the molar ratio 4:3 or by react ion of Ba3P2 and Ba5P4 in the molar ratio 1:1 (steel ampoules with inn er corundum crucibles; 1490 K). The greyish black, easily hydrolysing compound crystallizes in a new structure type oP56. The structure show s two crystallographically independent dumbbells P-2(4-) (d(P-P) = 225 and 232 pm) and isolated ions P3- corresponding to (Ba2+)8(P24-)4(P3- )4. The partial structure of the Ba atoms forms a complex network of t rigonal prisms with tetrahedral and square pyramidal holes, as well as polyhedra with 14 faces (CN 10) which are icosahedron derivatives. Th e P3- anions center trigonal prisms and the 14 face polyhedron. The P- atoms of the P-2(4-) dumbbells center neighboring trigonal prisms with common square faces. (Pbam (no. 55); a = 1325.4(2) pm, b = 1 256.2(2) pm, c = 1127.3 pm; Z = 8).