Rare earth halides Ln4X5Z.: Part 1:: C and/orC2 in Ln4X5Z

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 degrees C < T < 1050 degrees C. They crystallize in the monoclinic space group C2/m. La4I5C1.5: a = 19.849(4) angstrom, b = 4.1410(8) angstrom, c = 8.956(2) angstrom, beta = 103.86(3)degrees, La4I5C2.0: a = 19.907(4) angstrom, b = 4.1482(8) angstrom, c = 8.963(2) angstrom, beta = 104.36(3)degrees, Ce4Br5C1.0: a = 18.306(5) angstrom, b = 3.9735(6) angstrom, c = 8.378(2) angstrom, beta = 104.91(2)degrees, Ce4Br5C1.5: a = 18.996(2)angstrom, b = 3.9310(3) angstrom, c = 8.282(7) angstrom, beta = 106.74(1)degrees, Pr4Br5C1.3: a = 18.467(2) angstrom, b = 3.911(1) angstrom, c = 8.258(7) angstrom, beta = 105.25(1)degrees and Pr4Br5C1.5: a = 19.044(2) angstrom, b = 3.9368(1) angstrom, c = 8.254(7) angstrom, beta = 106.48(1)degrees. In the crystal structure the lanthanide metals are connected to Ln(6)-octahedra centered by carbon atoms or C-2-groups. The Ln6-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 1.40 A. In the ionic formulation (Ln(3+))(4)(X-)(5)(C4-)(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.