Aluminium hydroxyfluorides

D. Damboumet, A. Demourgues, C. Martineau, S. Pechev, J. Lhoste, J. Majimel, A. Vimont, J.-C. Lavalley, C. Legein, J.-Y. Buzare, F. Fayon, A. Tressaud, Nanostmctured aluminium hydroxyfluorides derived from d-AW-, Chem. Mater, 20, 1459-1469 (2008). 

Another way to increase resolution while avoiding an excessively long experimental time is to constmct a two-dimensional one pulse (TOP) spectrum [21-23] from a conventional ID MAS spectrum. The TOP spectmm evidences the well-known narrowing of the inner satellite transition line width when the components are not well resolved on the N = 0 cross-section, the projection over the satelhte transitions (N 0) shows a much better resolution as shown in HS pyrochlore aluminium hydroxyfluoride [20] (Figure 5.6), nanostructured Al-based fluoride-oxide materials [24] and aluminium fluoride hydrate with cationic vacancies [25]. 

Nanostructured Aluminium Hydroxyfluorides and Aluminium Fluoride Hydrate with Cationic Vacancies... 

In this section, a description of the use of the microwave-assisted synthesis for the preparation of nanosized and crystalline aluminium-based fluorides is proposed. A detailed characterization of the solid obtained is also presented. Using this method, three different crystalline forms can be obtained (i) an aluminium (hydroxyl)-fluoride adopting the HTB type structure and labelled as /S-AlFs, (ii) a hydroxyfluoride adopting... 

Figure 2.4 Dependence of the X-ray diffraction powder pattern of the pyrochlore hydroxyfluoride on the nature of the aluminium precursor. For each X-ray diagram, the precursor and the specific surface area is noted...

Since it seems obvious that these new catalysts might be applied for other related reactions, we also tested aluminium and magnesium hydroxyfluorides for the cyclization of citronellal yielding ( )-isopolegol [21]. Some of these catalysts yielded extremely high chemo- and diasterioselectivity for ( )-isopolegol, which has not been achieved so far with other catalysts -not even with homogenous ones. 

In the second part (Section 5.3), the strong potential of these techniques for the study of functionalized Al-based inorganic fluorides, synthesized for their possible application as catalysts (fluorinated alumina and zeolites, high surface area aluminium trifluorides and nanostructured aluminium fluoride hydrates and hydroxyfluorides), is shown. The compounds used as model for the assignment of the V and Al NMR lines in these materials are also presented. 

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