SYNTHESIS OF TANTALUM TELLURIDES - THE CRYSTAL-STRUCTURE OF TA2TE3

Ta2Te3 Was prepared by reducing TaTe2 with tantalum at 1350 K in a sealed molybdenum crucible. Ta2Te3 disproportionates above 1420 K yielding the ditelluride and as yet unknown Ta6Te3. The stability limit for the substitutional sesquitellurides NbxTa2-xTe3 is reached at x almost-equal-to 1. The novel layered-type structure of Ta2Te3 (C 2/m, N = 4; a = 2049.5(3) pm, b = 349.96(4) pm, c = 1223.7(2) pm, beta = 143.74(1)0 (Guinier), N(I0) = 762 with I0 > 2-sigma(I0), 32 variables, R = 0.032) can be considered a stuffed variant of a molybdenite structure type. It consists of corrugated layers 2 infinity(Te-Ta4/3-Te) which, according to the shortest interlayer contacts Te-Te (372.9 pm), order via van der Waals interactions. Extended homonuclear bonding regions (297.1 pm less-than-or-equal-to d(Ta-Ta) less-than-or-equal-to 309.7 pm) within the metal layers contribute to the stability of the metallic sesquitelluride.