The Phosphides U6Fe30P19 and U6Co30P19 with the ­Yb6Co30P19 Structure Type

Powders of U6Fe30P19 and U6Co30P19 were synthesized through the use of tin fluxes. Examination of these powders at 298 K by the Guinier technique led to lattice parameters in the hexagonal system for U6Fe30P19 of a = 14.762(2) Å, c = 3.6315(4) Å, c/a = 0.2460, V = 685.3 Å3 and for U6Co30P19 of a = 14.722(3) Å, c = 3.6355(6) Å, c/a = 0.2469, V = 682.4 Å3. Single crystals of U6Fe30P19 were synthesized and its structure was determined. U6Fe30P19 crystallizes in the space group C1,3h – Pequation image of the hexagonal system in the Yb6Co30P19 structure type with one formula unit in a cell of dimensions determined at 100 K of a = 14.7206(4) Å, c = 3.6243(1) Å, c/a = 0.2462, V = 680.15(4) Å3. The asymmetric unit of U6Fe30P19 comprises two U, ten Fe, and seven different P atoms. Each U atom is situated in a trigonal prism of six P atoms; each Fe atom is coordinated either by a tetrahedron or a square pyramid of P atoms. The distances are all less than 2.9 Å. In addition, the structure contains numerous Fe–Fe bonds covering the range from 2.55 to 2.71 Å. The proper space group of the Yb6Co30P19 structure type is discussed.