Platonic Relationships in Metal Phosphonate Chemistry: Ionic Metal Phosphonates

Abstract

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 (Mg2+, Ca2+, Sr2+ and Ni2+) and the phosphonic acids: p-aminobenzylphosphonic acid (H2PABPA), tetramethylenediamine-tetrakis(methylenephosphonic acid) (H8TDTMP), and 1,2-ethylenediphosphonic acid (H4EDPA). The compounds isolated and structurally characterized are [Mg(H2O)6]·[HPABPA]2·6H2O, [Ca(H2O)8]·[HPABPA]2, [Sr(H2O)8]·[HPABPA]2, [Mg(H2O)6]·[H6TDTMP], and [Ni(H2O)6]·[H2EDPA]·H2O. Also, the coordination polymer {[Ni(4,4’-bpy)(H2O)4]·[H2EDPA]·H2O}n was synthesized and characterized, which contains a bridging 4,4’-bipyridine (4,4’-bpy) ligand forming an infinite chain with the Ni2+ cations. All these compounds contain the phosphonate anion as the counterion to charge balance the cationic charge originating from the metal cation.

Influence of the Substituent’s Size in the Phosphinate Group on the Conformational Possibilities of Ferrocenylbisphosphinic Acids in the Design of Coordination Polymers and Metal–Organic Frameworks

“…In the case of 2 with Mn(II), even the presence of 4,4′-bipyridine leads to a polymer of type 6c , while in the case of Ni(II), polymer 10 ( Figure 12 ) is formed, where the ferrocene fragment is not even included in the coordination chain of the polymer and acts as a counterion in the nickel-4,4′-bipyridine chain. The similar compounds contain the phosphonate anion as the counterion to charge balance the cationic charge originating from the metal cation was observed in paper [ 65 ].…”

“…In the case of 2 with Mn(II), even the presence of 4,4′-bipyridine leads to a polymer of type 6c, while in the case of Ni(II), polymer 10 (Figure 12) is formed, where the ferrocene fragment is not even included in the coordination chain of the polymer and acts as a counterion in the nickel-4,4′-bipyridine chain. The similar compounds contain the phosphonate anion as the counterion to charge balance the cationic charge originating from the metal cation was observed in paper [65] The structure of polymer 10 is composed of parallel straight chains of Ni-complex and ferrocene molecules linked by hydrogen bonds between oxygen atom of phosphinate group and water molecules. Both chains run in the [010] direction (Figure 12).…”

Nanoporous Metal Phosphonate Hybrid Materials as a Novel Platform for Emerging Applications: A Critical Review

“…[203] These observations have well witnessed tremendous research breakthroughs in various applications involved in well-established fields and emerging technologies owing to the fascinating pore properties, the structural periodicity and versatile skeletons of porous metal phosphonates. [204][205][206] All in all, nanoporous metal phosphonate hybrid materials, as a novel platform, are promoting the innovation and technological revolution in chemistry, materials science, polymers and other interdisciplines, as well as the burgeoning progress of multifunctional porous materials in various areas.…”

Coordination Compounds of 9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐Oxide (DOPO) Ligands: Extremely High Thermostability and Ligand Oxidation in the Solid State

“…Alkaline metal and alkaline earth metal salts of diorganylphosphinic acids are known for their flame retardant formulations in polyester and polyamides. [4c] Demadis et al reported the synthesis of different metal phosphonate salts containing PABPA, EDPA, TDTMP and EDPA as ligands with magnesium, calcium strontium and nickel as metal ions where the affinity of the metal ions for water is higher than for the phosphonate containing ligands. A coordination polymer was obtained for Ni‐bpy‐EDPA, in which the affinity of the metal ion for 4,4'‐bpy as ligand is higher than the affinity for the phosphonate ligand.…”