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Właściwości koordynacyjne ligandów z ugrupowaniem fosfonowym z wybranymi jonami metali

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Kamecka A. , Kurzak B.

tom [Z] 57, 9-10

797--825

Aminopolyphosphonic acids and their derivatives have received considerable attention because of their interesting biological activity and a wide range of uses for industrial, chemical, agricultural and pharmacological purposes. The area of metal phosphonate chemistry has developed significantly in the last three decade. The coordination chemistry of this group of ligands is rich due to their versatility in adopting monodentate, bridging and chelating modes of coordination. Phosphonates and aminophosphonates are potent chelating agents for variety metal ions including the alkaline earth ions, the divalent ions as well as the trivalent ions. In this article we are summarizing and discussing the acid-base properties and the metal ion-coordinating properties of compounds involving one, two or more phosphonic groups. This work is aimed at being brief indicating the main achievements in researches over coordination preferences of this group of ligands. The present considerations are restricted to complexes in solution, involving the alkaline earth ions and the divalent ions of the second half of the 3d series as well as Zn2+ and Cd2+. The acid-base properties of the considered ligands depend on many factors such as the number of phosphonic groups in one molecule, the presence of other functional groups (e.g. COOH, NH3+, OH), the distance between functional groups and electronic effects of the substituents. These ligands contain a range of potential donor atoms. As a result, various bonding modes for a given chelating ligand are involved, and are reviewed with reference to ligand structure and the resulting coordination complexes. It is shown that depending on the pH and the nature of the metal ion in solution these ligands can bind to a metal ion via oxygen(s) (mostly with alkaline earth ions), and in a N,O bonding mode (usually with d metals). Coordination properties of phosphonic and aminophosphonic acids are important factors to understand the role of the ligands and metal ions in biological systems.