Preyssler anion

Figure 2.1 Structure of (a) terbium phthalocyaninato derivative, (b) [Ln(W5018)2]9 ion, (c) [Ln(P2-SiW11039)2]13 ion and (d) Preyssler anion [l nP5W30O110]12-.

This procedure has been applied to other symmetries such as the well-known Preyssler anion [LnP5W30O110]12-, LnW30 (Figure 2.Id) [9]. This POM has a central coordination site with an unusual, fivefold axial symmetry. In spite of the low symmetry provided by this anion, we have observed that the dysprosium and holmium derivatives behave as SMMs, exhibiting slow relaxation of the magnetization. The remarkable difference between this system and the previous... 

Figure 5.10 The structure of [ Ce(H20)s 4 Na(H20)P5W3oOno ] cluster [35]. (Reprinted from Inorganica Chimica Acta, 360, no. 6, Y. Lu, Y.G. Li, et al., A new family of polyoxometalate compounds built up of Preyssler anions and trivalent lanthanide cations, 2063-2070 (Figure 1), 2007, with permission from Elsevier.)...

Nd2(H20)i4 Na(H20)P5W3oOiio ] shows a one-dimensional chain structure built from Preyssler anions [Na(H20)P5W3oOno] " linked by neodymium cations. In the complex, the adjacent [Na(H20)P5W3oOno] clusters are linked to each other about a center of symmetry... 

Lu, Y, Li, Y, Wang, E. et al. (2007) A new family of polyoxometalate compounds built up of Preyssler anions and trivalent lanthanide cations. Inorganica Chimica Acta, 360, 2063—2070. 

The Preyssler anion, [Na(H20)P5W3o0110]14. The central sphere locates the water molecule... 

Four of the possible six possible skeletal isomers having the Wells-Dawson structure, as exemplified by [EgWigOgz] (E = P or As), have been structurally identified. The so-called Preyssler anion was structurally identified as [ Na(H2 0) P5W3oOiio] , itbeing shown that the Na(H2 0)+ group was tightly bound in the center of the cluster. However, under forcing conditions, the aqua-sodium cation could be replaced by Ca +, trivalent lanthanide cations and some tetravalent actinide cations, all of which have similar ionic radii... 

Bamoharram, F.F., Heravi, M.M., Roshani, M., Gharib, A., and Jahangir, M. 2006a. A catalytic method for synthesis of y-butyrolactone, e-caprolactone and 2-cumaranone in the presence of Preyssler s anion, [NaPjWjQOjjQ], as a green and reusable catalyst. Journal of Molecular Catalysis A Chemistry, 252 90-95. 

The title anion, first prepared by C. Preyssler, is formed as a by-product in the synthesis of the CP2W,8062] anion. It is one of the largest known... 

FIGURE 4 Structures of a-Keggin (A)-, Wells-Dawson (B)-, and Preyssler (C)-typed frameworks. Eu is co-ordinated by oxygen atoms of mono-lacunary ligands for a-Keggin and Wells-Dawson frameworks, in contrast with the case of the Preyssler framework where Eu is encapsulated in the centre of the anion. 

We report on the use of Preyssler s anion and HPA catalysts for obtaining substituted flavones and chromones for the cyclization of l-(2-hydroxyphenyl)-3-ar-yl-l,3-propanediones. The reactions were performed using chloroform as a solvent at reflux temperature conditions and in the absence of solvent, at 110°C. We had excellent yields and high selectivity at these conditions. The presented synthetic method is a simple, clean, and environmentally friendly alternative for synthesizing substituted flavones and chromones (Scheme 3.19) [59]. 

The obtained data vividly indicated that sodinm 30-tungstopentaphosphate, [NaP-jWjqOjj J, the so-called Preyssler s anion, with high hydrolytic (pH 0-12) and thermal stability is the catalyst of choice. This catalyst catalyzed the synthesis of other coiunarin derivatives la-f and 2 in high yields and good selectivity [95] (Scheme 3.35). 

A Catalytic Method for Synthesis of y-butyrolactone, c-caprolactone, and 2-cumaranone in the Presence of Preyssler s Anion, [NaPgWj OjjJ, as a Green and Reusable Catalyst... 

Preyssler s anion, [NaPjWjgOjjQl, was used as catalyst for the oxidation of aromatic aldehydes to related carboxylic acids using hydrogen peroxide as an oxidizing agent, under microwave irradiation or at 70°C. Oxidation of aldehydes is a surface type reaction and with Preyssler s anion, it produces the highest yields (Bamoharram et al., 2006). 

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