TERNARY SULFIDES OF URANIUM AND PALLADIUM .3. CHARACTERIZATION AND CRYSTAL-STRUCTURE OF PDU254

The new ternary U-Pd sulfide: PdU//2S//4 crystallizes in the orthorhombic system with a equals 10. 725(3) A, b equals 13. 148(4) A, c equals 8. 381(4) A, space group Fdd2, z equals 0 The structure was determined from 435 single-crystal X-ray reflections, and refined to R equals 0. 036. Uranium is coordinated by seven sulfur atoms with a mean distance d(U-S) equals 2. 78 A. Palladium is coordinated by four sulfur atoms with different Pd-S distances (2. 376 and 2. 595 A), and has two close uranium neighbors (d(Pd-2U) 3. 095 A. From crystal radii considerations it is concluded that PdU//2S//4 is an intermediate valence system, with some electron delocalization.