Anions isopoly

Isopolyanions. Isopoly anions are named by indicating with numerical prefixes the number of atoms of the characteristic element. It is not necessary to give the number of oxygen atoms when the charge of the anion or the number of cations is indicated. 

In recent times many advances in isopoly anion chemistry have been made by shifting reaction chemistry from aqueous to aprolic solution. This can often be done by employing a solubilizing cation such as tetrabutyfammonium ion. For example, when [(n-Bu)4N]0H and [(/i-Bu)4N][H7V ,OjK] are mixed in acetonitrile a new isopolyvanadate forms 53... 

The isopoly anions may be considered to be portions of a closest packed array of oxide ions with the metal ions occupying the octahedral holes. The edge-sharing array found in [V n02S]6 consists of ten octahedra stacked as shown in Fig. 16.10a. This seems to be the largest stacked-octahedral isopoly anion cluster compatible with metal-metal repulsions, and the remaining edge-shared structures represent portions of this unit.46... 

However, explanations for growth limitation based on repulsion of metal ions may be somewhat oversimplified. Elements other than vanadium, niobium, tantalum, molybdenum, and tungsten do not form isopoly anions. Other ions which have appropriate radii (e.g., Al,+, 67 pm Oa5+, 76 pm I7"1. 67 pm) for discrete isopoly anion formation instead form chains, sheets, or three-dimensional frameworks. Why does polymerization stop for isopoly anions An oxygen atom in a terminal position in an isopoly anion is strongly n bonded to a transition metal such as Mo(V ) or W (VI). These terminal oxygen atoms are never found trans to one another because they avoid... 

Fig. 16.11 The structures of two apex-shared dodecaiungstate isopoly anions (a) the paraiungslate B ion. IHjWuQol10-. (b) the melMungstcte ion. [HsWi20.iof. [From Lipscomb, W. N lucre. Chen. >965,4. 132. Reproduced with permission.]...

And there is a range of heteropoly- and isopoly-anion compounds of Mn,v with V, Nb, Ta, Mo and W (Table 26), most of which appear to be [Mn06] species. 

Figure 18-C-3 Some of the important isopoly anion structures. Structures known only for molybdates or tungstates are [HjWjjC ]10 shown at top and bottom.

NMR spin-spin coupling and induced shifts in oxovanadium(iv) complexes have been reviewed. (61,61a) spectra of VO2 and a variety of heteropoly- and isopoly-anions (e.g. VO , VioOfg ) have been measured. A linear correlation is found between the measured shifts and the averaged g-factors of the reduced forms of the ions with having an oxidation state of -1-4. Some spirocyclic V(iv) compounds of the type [9] have been studied by ESR and H/ Si... 

Isopoly Anions Transition melaK in their higher o Kl.iiion states are fcrmtiily similar to nonmeuils... 

Reduced and Mixed-valence Isopoly anions 4.10.2.6.1 Vanadates... 

Figure 22.3 The structures of some isopoly-anions in the solid state using, where relevant, the conventional representation in which each polyhedron contains a metal atom and each vertex of a polyhedron represents an oxygen atom.

The structures of both the heptamolybdate and octamolybdate ions in crystals are discussed on page 954 in relation to other heteropoly and isopoly anion structures. 

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