The cyclic 48-tungsto-8-phosphate [H7P8W48O184]33− Contant-Tézé polyanion and its derivatives [H6P4W24O94]18− and [H2P2W12O48]12−: structural aspects and reactivity

Abstract

Polyoxometalates (POMs) are discrete, anionic metal-oxo clusters of early transition metals in high oxidation states (e.g., WVI, MoVI, VV) usually comprised of edge- and corner-shared MO<inf>6</inf> octahedra. Lacunary POMs are defect heteropolyanions mainly of the Keggin or Dawson type, and they can be formed by the loss of one or more MO<inf>6</inf> octahedra by controlled base hydrolysis. The largest subclass of POMs are tungstophosphates, and several lacunary derivatives are known, such as the Keggin-based [PW<inf>11</inf>O<inf>39</inf>]7− and [PW<inf>9</inf>O<inf>34</inf>]9−, and the Dawson-based [P<inf>2</inf>W<inf>17</inf>O<inf>61</inf>]10− and [P<inf>2</inf>W<inf>15</inf>O<inf>56</inf>]12−. This review is based on the cyclic 48-tungsto-8-phosphate [H<inf>7</inf>P<inf>8</inf>W<inf>48</inf>O<inf>184</inf>]33− (P<inf>8</inf>W<inf>48</inf>) as well as its smaller derivatives [H<inf>6</inf>P<inf>4</inf>W<inf>24</inf>O<inf>94</inf>]18− (P<inf>4</inf>W<inf>24</inf>), and [H<inf>2</inf>P<inf>2</inf>W<inf>12</inf>O<inf>48</inf>]12− (P<inf>2</inf>W<inf>12</inf>), with a focus on structural aspects, solution stability and reactivity. All three polyanions can be considered as inorganic multidentate O-donor ligands that coordinate with d, f or p-block metal ions. Here we provide a comprehensive overview of guest metal-containing derivatives of the P<inf>8</inf>W<inf>48</inf> wheel, the P<inf>4</inf>W<inf>24</inf> half-wheel and the P<inf>2</inf>W<inf>12</inf> quarter wheel. The structures containing P<inf>2</inf>W<inf>12</inf> as a building unit are presented in a sequence of increasing number of POM units in the resulting assembly. Transition metal-containing POMs have been of interest for decades due to their remarkable capability of forming novel and unexpected structures associated with interesting and relevant physicochemical properties (e.g., catalysis, magnetism, biomedicine, electrochemistry), and this also applies for derivatives containing P<inf>8</inf>W<inf>48</inf>, P<inf>4</inf>W<inf>24</inf> and P<inf>2</inf>W<inf>12</inf> © 2025 The Royal Society of Chemistry.