Studies On Some Acid Divalent-Metal Nitrilotriacetate Complexes

Abstract

IR and 1H-NMR studies on nitrilotriacetic acid (H3NTA) suggest that the acid exists in the zwitterion form, which allows the existence of intermolecular hydrogen bonding. A tetrahedral structure is established for eleven (1:1) anhydrous acid-metal (II) nitrilotriacetates complexes. The ten Dq values for the colored complexes were determined spectrophotometrically. The pKa values for the eleven acid metal complexes [M(HNTA)].(OH2)3] were determined and compared with the corresponding pKa values of the [M(OH2)n]+2 ions and also with the log β1 values of the corresponding [M(NTA)]- complexes. X-ray diffraction studies on the ligand and on eight of these complexes are described.

Keywords

• nitrilotriacetic acid
• nitrilotriacetates complexes
• pKa values
• X-ray diffraction