THE CRYSTAL-STRUCTURES OF TH4FE17P10O1-X AND THFE5P3

The new compounds Th4Fe17P10O1-x and ThFe5P3 were prepared in well-crystallized form using a tin flux. Their crystal structures were determined from single-crystal X ray data. Th4Fe17P10O1-x (x = 0.36(3)) is monoclinic: C2/m, a = 2464.8(6) pm, b = 377.3(1) pm, c = 930.3(2) pm, beta = 91.25(3)degrees, Z = 2, R = 0.024, ThFe5P3 has a YCo5P3-type structure: Pnma, a = 1210.8(2) pm, b = 376.7(1) pm, c = 1058.1(4) pm, Z = 4, R = 0.024. The compounds belong to a large family of structures with a metal :nonmetal ratio of exactly or nearly 2:1, In these structures all phosphorus atoms are surrounded by six metal atoms forming a trigonal prism with three additional metal atoms capping the rectangular faces of the prism. The iron atoms in Th4Fe17P10O1-x and ThFe5P3 have tetrahedral and square-pyramidal phosphorus coordination, One iron atom of Th4Fe17P10O1-x is situated in a rectangle of phosphorus atoms. Both compounds have numerous iron-iron bonds with distances as short as 238 pm. The oxygen atoms of Th4Fe17P10O1-x are octahedrally coordinated by four thorium and two iron atoms. (C) 1995 Academic Press, Inc.