Platonic Relationships in Metal Phosphonate Chemistry: Ionic Metal Phosphonates
oleh: Konstantinos Xanthopoulos, Zafeiria Anagnostou, Sophocles Chalkiadakis, Duane Choquesillo-Lazarte, Gellert Mezei, Jan K. Zaręba, Jerzy Zoń, Konstantinos D. Demadis
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2019-06-01 |
Deskripsi
Phosphonate ligands demonstrate strong affinity for metal ions. However, there are several cases where the phosphonate is found non-coordinated to the metal ion. Such compounds could be characterized as salts, since the interactions involved are ionic and hydrogen bonding. In this paper we explore a number of such examples, using divalent metal ions (Mg<sup>2+</sup>, Ca<sup>2+</sup>, Sr<sup>2+</sup> and Ni<sup>2+</sup>) and the phosphonic acids: <i>p</i>-aminobenzylphosphonic acid (H<sub>2</sub>PABPA), tetramethylenediamine-<i>tetrakis</i>(methylenephosphonic acid) (H<sub>8</sub>TDTMP), and 1,2-ethylenediphosphonic acid (H<sub>4</sub>EDPA). The compounds isolated and structurally characterized are [Mg(H<sub>2</sub>O)<sub>6</sub>]·[HPABPA]<sub>2</sub>·6H<sub>2</sub>O, [Ca(H<sub>2</sub>O)<sub>8</sub>]·[HPABPA]<sub>2</sub>, [Sr(H<sub>2</sub>O)<sub>8</sub>]·[HPABPA]<sub>2</sub>, [Mg(H<sub>2</sub>O)<sub>6</sub>]·[H<sub>6</sub>TDTMP], and [Ni(H<sub>2</sub>O)<sub>6</sub>]·[H<sub>2</sub>EDPA]·H<sub>2</sub>O. Also, the coordination polymer {[Ni(4,4’-bpy)(H<sub>2</sub>O)<sub>4</sub>]·[H<sub>2</sub>EDPA]·H<sub>2</sub>O}<sub>n</sub> was synthesized and characterized, which contains a bridging 4,4’-bipyridine (4,4’-bpy) ligand forming an infinite chain with the Ni<sup>2+</sup> cations. All these compounds contain the phosphonate anion as the counterion to charge balance the cationic charge originating from the metal cation.