Crystal structure of the isomorphous complexes tetraaquabis(2,6-dihydroxybenzoato-O)(2,6-dihydroxybenzoato-O,O)terbium(III) and holmium(III) dihydrate

The structures of isomorphic Tb(III) and Ho(III) complexes with 2,6-dihydro xybenzoic acid of formula [Tb(C7H5O4)(3) . 4H(2)O] . 2H(2)O and [Ho(C7H5O4) (3) . 4H(2)O] . 2H(2)O has been determined by X-ray diffraction and refined to a residual R = 0.030 for 5376 observed reflections and R = 0.0284 for 5 660 observed reflections, for Tb(III) and Ho(III) complexes, respectively. Crystals are triclinic, space group P (1) over bar with a =10.748(2), b=11. 309(2), c=12.452(2) Angstrom, alpha=82.28(3), beta = 73.05(5), gamma =68.27 (3)degrees for Tb(III) and a = 10.731(2), b = 11.269(2), c = 12.436(2) Angs trom, or alpha = 82.25(3), beta = 72.92(3), gamma = 68.46(3)degrees for Ho( III). In the structure of these monomeric complexes the metal ions are coordinate d by oxygen atoms of one bidentate chelating and two monodentate carboxylat e groups and four molecules of water. Tb-O distances are in the range 2.323 (3)-2.506(3) Angstrom and Ho-O 2.297(3)-2.486(3) Angstrom. The crystal stru cture, consisting of discrete units of neutral complexes with two molecules of water of crystallization is stabilized by intra- and intermolecular hyd rogen bonds.