Lanthanum ruthenium boride, LaRu4B4

LaRu4B4 is tetragonal with space group, P42/n, a = 7.541 (3), c = 4.012 (1) A, Z = 2, Dx = 8.54 Mg m-3, single-crystal counter dflf\ F/ < h\ Fo = 0.05 for reflexions with\Fo > 2 sigma (Fo). The Ru atoms form infinite chains of edge-sharing tetrahedra \d(Ru-Ru) = (2), 4 x 2.772 (2) A\ which are separated by strings of La atoms \d(La-La) = 4.012 (1) A\ and by pairs of B atoms \d(B-B) = 1.83 (2) A\. The compound is isostructural with NdCo4B4. A factor which favours this structure is the relative size of the rare-earth atoms with respect to the size of the transition-metal atoms. 8 ref.--AA