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Seltenerdhalogenide Ln 4 X 5 Z. Teil 1: C und/oder C 2 in Ln 4 X 5 Z

2008; Wiley; Volume: 634; Issue: 3 Linguagem: Inglês

10.1002/zaac.200700500

1521-3749

Hansjürgen Mattausch, M.C. Schaloske, Constantin Hoch, Chong Zheng, Arndt Simon,

Iron-based superconductors research

Abstract Rare Earth Halides Ln 4 X 5 Z. Part 1: C and/or C 2 in Ln 4 X 5 Z The compounds Ln 4 X 5 C n (Ln = La, Ce, Pr; X = Br, I and 1.0 < n < 2.0) are prepared by the reaction of LnX 3 , Ln metal and graphite in sealed Ta‐ampoules at temperatures 850 °C < T < 1050 °C. They crystallize in the monoclinic space group C 2/ m . La 4 I 5 C 1.5 : a = 19.849(4) Å, b = 4.1410(8) Å, c = 8.956(2) Å, β = 103.86(3)°, La 4 I 5 C 2.0 : a = 19.907(4) Å, b = 4.1482(8) Å, c = 8.963(2) Å, β = 104.36(3)°, Ce 4 Br 5 C 1.0 : a = 18.306(5) Å, b = 3.9735(6) Å, c = 8.378(2) Å, β =104.91(2)°, Ce 4 Br 5 C 1.5 : a = 18.996(2) Å, b = 3.9310(3) Å, c = 8.282(7) Å, β = 106.74(1)°, Pr 4 Br 5 C 1.3 : a = 18.467(2) Å, b = 3.911(1) Å, c = 8.258(7) Å, β = 105.25(1)° and Pr 4 Br 5 C 1.5 : a = 19.044(2) Å, b = 3.9368(1) Å, c = 8.254(7) Å, β = 106.48(1)°. In the crystal structure the lanthanide metals are connected to Ln 6 ‐octahedra centered by carbon atoms or C 2 ‐groups. The Ln 6 ‐octahedra are condensed via opposite edges to chains and surrounded by X atoms which interconnect the chains. A part n of isolated C‐atoms is substituted by 1‐ n C 2 ‐groups. The C‐C distances range between 1.26 and 1.40Å. In the ionic formulation (Ln 3+ ) 4 (X − ) 5 (C 4− ) n (C 2 m− ) 1− n ·e − with 0 < n < 1 and m = 2, 4, 6 (C 2 2− , C 2 4− C 2 6− ), there are 1 < e − < 5 electrons centered in metal‐metal bonds.