The structures of two complexes of neodymium(III) with pyridine-2,6-dicarboxylic acid of formula (NH4)(3)[Nd(C7H3NO4)(3)]. 7H(2)O (1) and (NH4)[Nd-3(C7H3NO4)(5) . 8H(2)O]. 5H(2)O (2) have been determined by X-ray diffraction. Crystals of 1 are monoclinic, P2(1)/c, a 17.925(4), b = 10.198(2), c = 18.707(4)Angstrom, beta = 112.22(3)degrees Z = 4. Crystals of 2 are monoclinic C2/c, a = 22.205(4), b = 13.774(3), c = 17.783(4)Angstrom, beta = 112.55(3)degrees, Z = 4. Both structures were solved by the heavy-atom method and refined to R = 0.032 for 7568 reflections (1) and 0.030 for 3267 reflections (2). The water molecules and NH4+ groups in both crystals participate in a network of hydrogen bonds.
