Two new examples for the unusual R{sub 12}I{sub 17}Z{sub 2}-structure type: La{sub 12}I{sub 17}Fe{sub 2} and Ce{sub 12}I{sub 17}Mn{sub 2}
- Iowa State Univ., Ames, IA (United States)
Reactions of KI, La, LaI{sub 3}, and Fe in niobium tubes at 900{degrees}C yield black crystals of La{sub 12}I{sub 17}Fe{sub 2} which were characterized by single-crystal X-ray diffraction (triclinic, P1, Z = 1, a = 11.967(8), b = 11.851(6), c = 9.918(7) {angstrom}, {alpha} = 114.59(5){degrees}, {beta} = 104.83(6){degrees}, {gamma} = 93.05(5){degrees}, R(F)/R{sub w} = 3.8/4.3%). Similar experiments also gave the isostructural Ce{sub 12}I{sub 17}mn{sub 2} according to the Guninier powder pattern (a = 11.863(6), b = 11.840(6), c = 9.857(5) {angstrom}, {alpha} = 14.90(4){degrees}, {beta} = 104.47(4){degrees}, {gamma} = 93.28(4){degrees}). The Pr{sub 12}I{sub 17}Fe{sub 2}-type structure contains octahedral rare-earth-metal cluster units R{sub 6} centered by a transition-metal atom Z and sheathed by iodine atoms. These are closely linked by seven I{sup i-i} and one I{sup i-a-a} bridges that lead to the unusually low I:Pr ratio for phases with isolated clusters. The compounds reported here together with Pr{sub 12}I{sub 17}Z{sub 2}, Z = Fe, Re are the only phases known to adopt this structure type. The La{sub 12}I{sub 17}Fe{sub 2} phase for data are consistent with equal numbers of 17-e and 18-e (closed shell) clusters, with {mu} = 1.11 BM for the former.
- OSTI ID:
- 486251
- Journal Information:
- Journal of Solid State Chemistry, Vol. 125, Issue 2; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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