A new mononuclear gadolinium(III) complex [Gd(Hoda)(3)]. H(2)Oda . H2O (Koda = HO2CCH2OCH2CO2-) has been isolated from the reaction of Gd2O3 With oxydiacetic acid in aqueous solution. A single-crystal X-ray study features the nine-coordinate GdO9 core in a distorted tricapped trigonal-prism environment. The top and bottom triangles are defined by three carboxylate and three carbonyl oxygen atoms, respectively, and the capping positions, by three ether oxygens of three tridentate Hoda ligands.