Rh3B2-x, new structure type of binary borides with triclinic symmetry

New binary compound Rh3B2-x, x = 0.167 crystallizing with its own structure type has been observed from the as cast alloys. The compound has a limited thermal stability range: it was found to decompose after annealing at 800 degreesC for 20 days. The crystal structure was investigated by X-ray diffraction from two single crystals using different techniques: CAD-4 automatic diffractometer, a = 5.470(2) b = 6.816(3), c = 9.068(4), alpha = 110.74(3), beta = 94.81(3), gamma = 90.44(2), 107 refined parameters, R-1 = 0.0418, WR2 = 0.1087 for 1223 reflections with I > 2sigma(I-o), and BRUKER SMART AXS, a = 5.483(4), b = 6.818(6), c = 9.072 (7), a = 110.78(1), b = 94.73(1), g = 90.46(1) 107 refined parameters, R-1 = 0.040 1, wR(2) = 0.0959 for 943 reflections with I > 2sigma(I-o). The Rh3B2-x, structure (space group P (1) over bar, Pearson symbol aP30 - 1) is the first representative of structures with triclinic symmetry among binary borides and contains three different types of boron-boron aggregation: isolated boron atoms, B-B pairs and B-6 chain fragments.