Non-aqueous sol–gel synthesis of nano-structured metal fluorides

Rüdiger, Stephan; Groß, U.; Kemnitz, Erhard

doi:10.1016/j.jfluchem.2006.11.006

Cited by 96 publications

(59 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The F to OH ratio in the products formed this way should depend on the free Gibbs enthalpy of each reaction and on the reaction rate. In fact both, the thermodynamic data as well as the reaction rate (the fluorolysis rate for the Mg-system is about 10 times higher than the hydrolysis rate) let expect the domi nant formation of the metal fluoride [22]. However, by varying the H 2 O to HF-ratio in the hydrofluoric acid differently hydroxylated metal fluoride phases should be obtained.…”

Section: Hydroxylated Metal Fluoridesmentioning

confidence: 99%

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

et al. 2010

View full text Add to dashboard Cite

In this article, the high potential of the fluorolytic sol-gel process to synthesise nanoscopic metal fluorides with different acid-base properties is shown. These nanoscopic materials exhibit high potential to be used as heterogeneous catalysts due to their high surface areas and their tunable surface properties. Thus, for each specific reaction the required surface properties of the catalysts can be "adjusted" to achieve a high yield and selectivity of the desired product. As a consequence, a greener method of chemical production can be accomplished. Moreover the cheap and easy synthesis of the catalysts using basic chemicals makes them not only interesting for fundamental research but provides an easy transformation to industrial applications.

show abstract

Section: Hydroxylated Metal Fluoridesmentioning

confidence: 99%

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

et al. 2010

View full text Add to dashboard Cite

show abstract

“…[1] The principle is based on the reaction of a metal alkoxide with anhydrous HF in alcoholic solution, resulting in an exchange of -OR by -F (fluorolysis); this forms a metal fluoride sol, which, under appropriate conditions, can be converted into the corresponding nanoscopic, pure Lewis acid metal fluoride. [2] This method has been successfully employed for the synthesis of magnesium fluoride.…”

Section: Introductionmentioning

confidence: 99%

Novel Sol–Gel Synthesis of Acidic MgF_2−x(OH)_x Materials

Wuttke

Coman

Scholz

et al. 2008

Chemistry A European J

Self Cite

104

110

View full text Add to dashboard Cite

Novel magnesium fluorides have been prepared by a new fluorolytic sol-gel synthesis for fluoride materials based on aqueous HF. By changing the amount of water at constant stoichiometric amount of HF, it is possible to tune the surface acidity of the resulting partly hydroxylated magnesium fluorides. These materials possess medium-strength Lewis acid sites and, by increasing the amount of water, Brønsted acid sites as well. Magnesium hydroxyl groups normally have a basic nature and only with this new synthetic route is it possible to create Brønsted acidic magnesium hydroxyl groups. XRD, MAS NMR, TEM, thermal analysis, and elemental analysis have been applied to study the structure, composition, and thermal behaviour of the bulk materials. XPS measurements, FTIR with probe molecules, and the determination of N(2)/Ar adsorption-desorption isotherms have been carried out to investigate the surface properties. Furthermore, activity data have indicated that the tuning of the acidic properties makes these materials versatile catalysts for different classes of reactions, such as the synthesis of (all-rac)-[alpha]-tocopherol through the condensation of 2,3,6-trimethylhydroquinone (TMHQ) with isophytol (IP).

show abstract

“…By using anhydrous hydrogen fluoride (aHF) in a suitable organic solvent, the metal-alkoxide bond undergoes fluorolysis instead of hydrolysis. [1,2] Metal fluorides with remarkably high surface areas (hs-MF x ) are thereby formed. Unlike those obtained by conventional methods, nanoscopic metal fluorides are extremely strong Lewis acids and are of interest for heterogeneous catalysis.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…[6] The asymmetric unit of the structure contains a cation, [Mg 3 F(m 3 -OMe) 2 À anions by pairs of hydrogen bonds ( Figure 1). The cationic complex contains two equivalent trinuclear fragments which are fused together by a dimetalladifluoro four-membered ring (Mg1F) 2 3À . [7] The bridging arrangement of the metal atoms in 1 has been found in the structure of the calcium ethoxide [Ca 6 O 2 (OEt) 8 ]·14 EtOH, but in that case, the bridging is with m 4 oxygen atoms instead of fluorine atoms.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Mg₆F₂(OMe)₁₀(MeOH)₁₄—An Alkoxide Fluoride of an Alkaline Earth Metal

et al. 2007

Self Cite

View full text Add to dashboard Cite

Sol-gel synthesis, which was developed for metal oxides, can also be applied to the synthesis of nanoscopic metal fluorides. By using anhydrous hydrogen fluoride (aHF) in a suitable organic solvent, the metal-alkoxide bond undergoes fluorolysis instead of hydrolysis. [1,2] Metal fluorides with remarkably high surface areas (hs-MF x ) are thereby formed. Unlike those obtained by conventional methods, nanoscopic metal fluorides are extremely strong Lewis acids and are of interest for heterogeneous catalysis. Furthermore, the ease of preparation of stable metal fluoride colloidal solutions (sols) opens the way to new applications, such as optical or protective corrosion-resistant coatings. Owing to the highly distorted structures of the nanoscopic phases formed, insight into the mechanism of the process was only available by theoretical calculations and MAS-NMR investigations.[3] We have isolated a monofluorinated intermediate from the aHF-Al-(OiPr) 3 -system, [4] which thus confirmed the theoretical predictions.[3] During our investigations into the synthesis of hsMgF 2[5] from the reaction of Mg(OCH 3 ) 2 with alcoholic aHF solution, it was possible to obtain an intermediate which was identified as a magnesium alkoxide fluoride. Herein we report the selective synthesis of the first alkoxide fluoride of an alkaline earth metal and its double-cubane structure with unusual bridging fluoride ligands.[ À anions by pairs of hydrogen bonds (Figure 1). The cationic complex contains two equivalent trinuclear fragments which are fused together by a dimetalladifluoro four-membered ring (Mg1F) 2 . The MgÀF bonds are 213.8 (1) 3À . [7] The bridging arrangement of the metal atoms in 1 has been found in the structure of the calcium ethoxide [Ca 6 O 2 (OEt) 8 ]·14 EtOH, but in that case, the bridging is with m 4 oxygen atoms instead of fluorine atoms.[8] It is worth noting that both the Mg2 and Mg3 cubane fragments in the hexanuclear magnesium cage of compound 1 stem from the cubane structure of the reactant. Indeed, if no HF is Figure 1. The structure of 1 with a hexanuclear dication and two anionic MeO···HOMe units connected to the cation by a total of four hydrogen bonds. The methyl hydrogen atoms are omitted for clarity.

show abstract

Non-aqueous sol–gel synthesis of nano-structured metal fluorides

Cited by 96 publications

References 39 publications

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Novel Sol–Gel Synthesis of Acidic MgF_2−x(OH)_x Materials

Mg₆F₂(OMe)₁₀(MeOH)₁₄—An Alkoxide Fluoride of an Alkaline Earth Metal

Contact Info

Product

Resources

About

Non-aqueous sol–gel synthesis of nano-structured metal fluorides

Cited by 96 publications

References 39 publications

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Sol–gel prepared nanoscopic metal fluorides – a new class of tunable acid–base catalysts

Novel Sol–Gel Synthesis of Acidic MgF2−x(OH)x Materials

Mg6F2(OMe)10(MeOH)14—An Alkoxide Fluoride of an Alkaline Earth Metal

Contact Info

Product

Resources

About

Novel Sol–Gel Synthesis of Acidic MgF_2−x(OH)_x Materials

Mg₆F₂(OMe)₁₀(MeOH)₁₄—An Alkoxide Fluoride of an Alkaline Earth Metal