The Thorium Transition Metal Borides Th2TB10 (T = Fe, Co, Ni) with a Structure Very Similar to that of CaB6

Crystal Structure, Polyborides The title compounds have been prepared by arc-melting cold-pressed pellets of the elemen­ tal components. They crystallize with a new structure type, which was determined from single­ crystal X-ray diffractometer data of Th2NiB1(): Pbam, a = 564.6(2) pm, b = 1120.4(3) pm, c = 417.3(1) pm, Z = 2, R = 0.020 for 748 structure factors and 25 variable parameters. The structures of Th2FeB |0 (a = 562.7(1) pm, b = 1126.1(3) pm, c = 418.3(2) pm) and Th2CoB1() (a = 562.4(1) pm, b = 1122.8(2) pm, c = 418.5(1) pm) were refined from single-crystal data to residuals of 0.025 (921 F values) and 0.032 (911 F values). The lattice of these ternary borides may be derived from that of ThB6 (Th2B12) with the cubic CaB6 type structure by replacing two of the linking boron atoms of adjacent B6 octahedra by a transition metal atom.