Rare earth osmium carbides Ln{sub 5}Os{sub 3}C{sub 4-x} (Ln = La-Nd, Sm) with a new type of filled Mn{sub 3}Si{sub 3} structure
- Universitaet Muenster (Germany)
The five compounds Ln{sub 5}Os{sub 3}C{sub 4-x} (Ln = La-Nd, Sm) have been prepared by arc-melting cold-pressed pellets of the elemental components and subsequent annealing. They crystallize with a new hexagonal structure type (P6{sub 3}/mcm, Z = 2), which has been determined from single-crystal X-ray data of Ln{sub 5}Os{sub 3}C{sub 3.25(4)} (a = 919.57(8) pm, c = 673.86(4) pm, R = 0.015 for 293 structure factors and 14 variable parameters) and also refined for Nd{sub 5}Os{sub 3}C{sub 3.17(7)} (a = 897.8(1) pm, c = 667.42(9)pm, R = 0.028, 440 F values, 14 variables). The metal positions correspond to the positions of the Mn{sub 5}Si{sub 3} structure. The carbon position of the Mo{sub 5}Si{sub 3}C{sub 1-x} structure is partially filled. The three additional carbon atoms of the formula La{sub 5}Os{sub 3}C{sub 4-x} occupy distorted octahedral La{sub 4}Os{sub 2} voids. The linear Os-C-Os units of these La{sub 4}Os{sub 2} octahedra have Os-C bond lengths of 191 pm. They are linked via common osmium atoms, thus forming a new kind of zig-zag-shaped polyanion. Using oxidation numbers the compound may be rationalized with the formula (5La{sup 3+}){sup +15} (Os{sub 3}C{sub 3}){sup -14}(0.25C{sup -4}){sup -1}.
- OSTI ID:
- 589017
- Journal Information:
- Journal of Solid State Chemistry, Vol. 131, Issue 1; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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