X-ray diffraction analysis of Co(HNta). 4H(2)O (I) (H(3)Nta = N(CH2COOH)(3)) revealed that its crystals are isostructural to a Zn analog and built from [Co(HNta)(H2O)(3)] complex molecules and crystallization water. The octahedral coordination of the Co atom includes two O atoms and an N atom provided by the chelating tridentate HNta(2-) ligand (average Co-O (Nta) 2.055 Angstrom and Co-N 2.205 Angstrom) and three O atoms of water molecules on the shared face (average Co-O(w) 2.105 Angstrom).