STRUCTURE OF GD4MO18O32

M(r) = 2867.90, monoclinic, P2/c, a = 9.847 (4), b = 5.6635 (7), c = 24.116 (11) angstrom, beta = 109.74 (2)-degrees, V = 1265.9 (8) angstrom 3, Z = 2, D(x) = 7.524 g cm-3, lambda(Mo K-alpha) = 0.71073 angstrom, mu = 188.71 cm-1, F(000) = 2536, T = 295 K, R = 0.035 for 2452 reflections with I > 2-sigma(I). Gd4Mo18O32 is isostructural with Ca5.45Mo18O32 and thus contains three kinds of infinite Mo chains: linear chains with alternate short and long Mo-Mo distances, chains of trans-edge-shared Mo4 rhomboidal clusters and finally chains of trans-edge-shared Mo6 octahedral clusters. While the Ca ions are delocalized in tunnels running along the b axis, the Gd ions show an order which induces a doubling of the b parameter and a changing of the space group from C2/m to P2/c.