Complex three-dimensional [Au3In5] polyanions in Ln(2)Au(3)In(5) (Ln = Ce,Pr, Nd, Sm)

The four isotypic title compounds were prepared from the elements by reacti ons in an are-melting furnace and subsequent annealing in sealed silica tub es at 970 K. The structure of the cerium compound was solved from single cr ystal X-ray diffractometer data: Pmn2(1), oP80, a = 465.27(8) pm, b = 5348. 3(9) pm, c = 740.5(1) pm, R1 = 0.0735, 5552 F-2 values, 243 variables, and BASF = 0.48(2). The structure of Ce2Au3In5 is composed of a complex three-d imensional [Au3In5] polyanion with a large variety of Au-In and In-In bonds . The cerium atoms are embedded in distorted pentagonal and hexagonal chann els within this polyanion. The crystal chemical relationship of the Ce(2)Au (3)In5, structure with the structures of the related stannides Y2Rh3Sn5 (oC 40, Cmc2(1)) and Yb2Pt3Sn5 (oP40, Pnma) is discussed. The differences in th ese three structure types result from a different ordering of the transitio n metal and tin(indium) atoms within the polyanionic network. Temperature-d ependent magnetic susceptibility measurements of Ce2Au3In5 show modified Cu rie-Weiss behavior with chi o = 5.2 x 10(-9) m(3)/mol, Theta=-16(1)K, and m u(exp) = 2.51(2) mu(B)/Ce, indicating trivalent cerium. No magnetic orderin g could be observed down to 2 K. (C) 1999 Academic Press.