Cobalt(II) Complexes with Nitrilotriacetic Acid, Nitrilopropionicdiacetic Acid and Nitriloisopropionicdiacetic Acid

Abstract The following cobalt (III) complexes containing nitrilotriacetic acid (NTA), nitrolopropionicdiacetic acid (NPDA) and nitriloisopropionicdiacetic acid (NIPDA) were prepared: (NH4)3[Co-(nta)2]·2H2O (pink) (I), NH4[Co(Hnta)2]·2H2O (pale pink) (II), K3[Co(npda)2]·2H2O (pink) (III), K[Co(Hnpda)2]·3H2O (pale pink) (IV), [Co(npda)(o-phen)]·H2O (reddish violet) (V), [Co-(npda)(bipy)] (reddish violet) (VI), K[Co(OH)(nipda) (H2O)]·H2O (bluish violet) (VII) and [Co-(nipda) (o-phen)] (reddish violet) (VIII); where nta, npda, nipda, o-phen and bipy are the abbreviations of nitrilotriacetate-, nitrilopropionicdiacetate-, nitriloisopropionicdiacetate-ion, o-phenanthroline and 2,2′-bipyridyl, respectively. On the basis of electronic spectra, it was found that complexes I to IV have the trans form, while complexes V, VI and VIII have the mer form structure with respect to the nitrogen atoms in the coordinating ligands. Complex VII showed a dehydrationdimerization reaction on heating by “Derivatograph”. Comparison of chemical and physical properties of the complexes with those of the corresponding chromium (III) complexes was made.