DE102006017582A1 - Process for the preparation of metal fluoride sols and gels - Google Patents

Abstract

The present invention relates to a method for producing metal fluoride sols and gels, comprising the steps of: a) providing a metal, b) providing a solution of hydrogen fluoride in a non-aqueous solvent and c) reacting the metal with the solution of hydrogen fluoride in one non-aqueous solvent to form a metal fluoride sol.

Description

The The present invention relates to a process for producing a Metal fluoride sols or a metal fluoride gel and its use.

metal fluorides are for the chemical, pharmaceutical and ceramics industries are of great importance. In particular, inorganic materials having a large surface area of of central importance, for example in heterogeneous catalysis, where the activity a catalyst in the high degree from its surface depends.

The preparation of metal fluorides can be carried out via the sol-gel route. Such a method is for example in the European patent application EP 04700458.5 described. According to the teaching disclosed therein, a metal fluoride precursor compound is typically provided, which is typically an alkoxide, an enolate or the salt of a carboxylic acid having a preferred chain length of 1 to 5 carbon atoms. Such a precursor compound is then reacted with anhydrous hydrogen fluoride in a suitable solvent to give, after removal of the solvent, an intermediate compound termed "precursor" EP 04700458.5 reacted in a second step with a fluorinating agent.

When in the European patent application EP 04700458.5 described method, the preparation of the metal fluoride precursor with a coordinatively bonded organic group is associated with a certain effort.

Of the The present invention is therefore based on the object, a method for the preparation of a metal fluoride sol and a metal fluoride gel or to provide a process for producing an amorphous metal fluoride.

It is a further object of the present invention to provide metal fluorides having a high surface area, preferably a surface area of, or greater than, 180 m ² / g, for example, for use as a catalyst. It is another object of the present invention to provide a coating based on amorphous metal fluoride and articles coated therewith.

• a) Bereitstellen eines Metalles,
• b) Bereitstellen einer Lösung von Fluorwasserstoff in einem nichtwäßrigen Lösungsmittel, und
• c) Umsetzen des Metalles mit der Lösung von Fluorwasserstoff in einem nichtwässrigen Lösungsmittel zur Ausbildung eines Metallfluorid-So1s.

This object is achieved in a first aspect by a metal fluoride sol and a metal fluoride gel comprising the steps:

• a) providing a metal,
• b) providing a solution of hydrogen fluoride in a non-aqueous solvent, and
• c) reacting the metal with the solution of hydrogen fluoride in a nonaqueous solvent to form a metal fluoride sol.

In one embodiment of the first aspect it is provided that the metal is a metal of the second, third or fourth main group or a subgroup of the periodic table, wherein the redox potential of the metal in the respective solvent is more negative than that of H ₂ .

In a preferred embodiment of the first aspect is provided that the metal from the group selected magnesium, calcium, strontium, barium, aluminum, zinc, Lead, rare earth includes.

In a preferred embodiment of the first aspect is provided that the metal from the group selected which includes magnesium and aluminum.

In a further embodiment of the first aspect, it is provided that the metal with the solution of Hydrogen fluoride in a stoichiometric based on hydrogen fluoride relationship or with a surplus is reacted on hydrogen fluoride.

In a still further embodiment of the first aspect, it is provided that the non-aqueous solvent an alcohol is selected is from the group comprising methanol, ethanol, propanol, isopropanol, Butanol, iso-butanol, tert-butanol, methoxyethanol, ethoxyethanol includes.

In a still further embodiment of the first aspect, it is provided that the alcohol up to 4% water contains.

In a still further embodiment of the first aspect, it is provided that the non-aqueous solvent an ether or a ketone or a sulfoxide.

In a still further embodiment of the first aspect, it is provided that the implementation of step c) at room temperature and standard pressure.

In a still further embodiment of the first aspect, it is provided that the metal fluoride sol or Metal fluoride gel has a solvent content of 50 mol% up 99.9 mol%, preferably from 70 mol% to 99 mol%.

In a still further embodiment of the first aspect, it is provided that the metal is an alloy or mixture of two or more metals.

In In a second aspect of the invention, the object is achieved by a metal fluoride sol or metal fluoride gel, obtainable according to a method according to the invention.

• d) Entfernung der volatilen Bestandteile aus dem in Schritt c) erhaltenen Reaktionsproduktes.

In yet another embodiment of the first aspect, it is contemplated that it further comprises the step of:

• d) removal of the volatile constituents from the reaction product obtained in step c).

In a preferred embodiment of the first aspect, it is provided that the volatile constituents be removed by a heat treatment.

In a preferred embodiment of the first aspect, it is provided that the heat treatment at a temperature of 30 to 500 ° C, preferably from 70 to 250 ° C he follows.

In an alternative embodiment of the first aspect, it is provided that the heat treatment takes place in vacuo at a pressure of 800 to 10 ^-3 mbar, preferably from 100 to 10 ^-1 mbar.

In an embodiment of the first aspect, it is provided that the method is a method for Preparation of an amorphous metal fluoride is.

In In a third aspect of the invention, the object is achieved by an amorphous metal fluoride obtained by a method according to the invention, in particular obtainable by a method according to the first aspect.

• a) Bereitstellen einer Oberfläche,
• b) Bereitstellen eines Metallfluorid-Sols oder Metallfluorid-Gels
• c) Beschichten des Metallfluorid-Gels oder Metallfluorid-Sols auf eine Oberfläche und
• d) optional Entfernen des Lösungsmittels aus dem Sol oder Gel.

In a fourth aspect of the invention, the object is achieved by a method for coating a surface, preferably for film-coating a surface, comprising the steps:

• a) providing a surface,
• b) providing a metal fluoride sol or metal fluoride gel
• c) coating the metal fluoride gel or metal fluoride sol on a surface and
• d) optionally removing the solvent from the sol or gel.

In a preferred embodiment of the fourth aspect, it is provided that the metal fluoride sol or the metal fluoride gel is provided by a method according to one embodiment of the invention or a metal fluoride sol or metal fluoride gel after a inventive embodiment is.

In a fifth Aspect of the invention, this object is achieved by a metal fluoride sol or gel according to the second aspect for the production of a coating, preferably a protective coating, an anti-reflection coating or a catalytically active layer on a suitable support.

In a sixth aspect of the invention, the object is achieved by the use of a metal fluoride according to the third aspect, for the preparation of ceramics, preferably transparent ceramics.

In In a further aspect of the invention, the object is achieved by the use of a metal fluoride gel or metal fluoride sol after the second aspect for the production of metal fluoride coated fibers or Waveguides.

In a seventh aspect of the invention, the object is achieved by an article comprising a metal fluoride sol or metal fluoride gel according to the second aspect, wherein the article is selected from the group comprising glass panes, cathode ray tubes, liquid crystal displays, metal surfaces and lenses.

These and further objects underlying the present invention are also solved by the subject matter of the independent claims. preferred embodiments arise from the dependent ones Claims.

The present inventors have surprising found that instead of using metal compounds with a coordinatively bonded organic group also metals directly as starting materials for the production of a metal fluoride sol or gel can be used can, then in turn for the production of an amorphous metal fluoride according to the present Invention can be used. According to the of is intended to teach the present inventors, preferably, the amount of solvent used in this reaction, based on the amount of metal, be so large that the product is liquid, d. H. a sol is and not a solid gel. Otherwise, the Implementation so strongly hampered by the resulting gel that it does not completely run out. The thus sol obtained can be easily concentrated to a gel provided the need for the preparation of a gel consists.

The present invention is further based on the surprising finding that, in the context of the process according to the invention, the nonaqueous solvent serving as solvent for the hydrogen fluoride acts so strongly solvating that the metal fluoride is converted into solution as a sol. This could be due to the previous Beo not to be expected from the following reasons.

In the reaction of a metal with hydrofluoric acid, there is often only a surface reaction of the metal, since the insoluble metal fluoride formed protects the underlying metal from further attack. This process is known as "passivation" and is observed, for example, with aluminum and magnesium or iron, whereas the use of aqueous hydrofluoric acid solution, also called hydrofluoric acid, often leads to a progressive attack, as the product formed is However, when water is replaced by a nonaqueous solvent such as alcohol, as taught in the present invention, an analogous behavior was not to be expected in that the metal fluorides in question, and especially neither aluminum fluoride nor magnesium fluoride, would be present in one It should also be noted that in the reaction of metal alkoxide with HF in alcohol, as for example in the European patent application EP 04700458.5 First, the sol or gel formed is not a true solution as in the case of water, and secondly, the sol / gel formation has just been understood to be bound to the starting metal-organic compound by partial recovery the structure initially only a partial substitution of the alkoxide groups by fluoride takes place. On the other hand, according to the previous understanding, the formation of a metal fluoride sol observed in aluminum and magnesium in the reaction with alcoholic HF solution could not be explained by a 2-step reaction in which the metal first reacts to form the respective alkoxide and second step reacts this alkoxide with HF, since alcohol as acid is much weaker than hydrofluoric acid. Against this background, it was therefore unlikely that the alcohol or non-aqueous solvents used as solvents for the hydrogen fluoride would have such a solvating effect that the metal fluoride would be converted into sol as a sol. The sol, in turn, can solidify into a gel as known to those skilled in the art and, for example, described in CJ Brinker and GW Scherer, Sol-Gel Science, Academic Press, Boston 1990.

As herein in a preferred embodiment used the term non-aqueous solvent, a solvent, the is free of water, preferably substantially free of Water. However, it is also within the scope of the present invention, that in some embodiments Water in the non-aqueous solvent is present, but the extent of the water content is such that the reaction described above and in particular the training the metal fluoride sol as disclosed herein, not or not essential being affected. Such amounts of water can, for example, thereby conditional that the for the implementation needed Hydrogen fluoride as highly concentrated, for example 70%, aqueous solution the non-aqueous System is added, especially if it is in the non-aqueous System to an alcoholic solvent or solvent system is.

Not last as a result of this reaction mechanism can be used as metals in the sense of present invention, all metals and mixtures or alloys be understood from such metals whose redox potential in respective non-aqueous solvent less than that of hydrogen, d. H. the less noble than hydrogen are.

On the basis of the method according to the invention for producing a metal fluoride sol and a metal fluoride gel, it is then possible to produce an amorphous metal fluoride having the properties described herein. This is based on the metal fluoride sol whose volatile components such as the nonaqueous solvent is removed, preferably under vacuum, whereby a solid is usually obtained. This solid corresponds in its applications according to EP 04700458.5 It should be noted that typically a certain content of the non-aqueous solvent used in the preparation of the metal fluoride sol remains further in the crystal structure and, as a result, the regular crystal structure is disrupted, ultimately resulting in amorphous character of the thus prepared metal fluoride conditionally.

The thus obtained amorphous metal fluoride may be reacted with any of those described in U.S. Pat EP 04700458.5 nachfluoriert be described methods. Preferably, the reaction with the fluorinating agent is carried out at an elevated temperature, but below the crystallization temperature of the metal fluoride. Thus, preferable temperature ranges are 350 ° C or less, 200 ° C or less and 100 ° C or 70 ° C or less. Typically, while still present, the content of organic compounds is reduced quantitatively, wherein preferably the carbon content based on the amorphous metal fluoride is less than 1%. A suitable fluorinating agent is typically CH _g Cl _h F _{4 -gh} , where the sum of g + h is equal to a number, preferably an integer from 1 to 3, or gaseous hydrogen fluoride. CH _g Cl _h F _{4 -gh} is typically gaseous, diluted with an inert gas such as N ₂ , the CH _g Cl _h F _4-gh partial pressure 5 to 1500 mbar, preferably example, 25 to 300 mbar, or in pure, not diluted form, at a temperature of 25 ° C to 450 ° C, preferably from 50 ° C to 300 ° C, can be used. The gaseous hydrogen fluoride is typically used diluted with an inert gas such as N ₂ or other gases, or used in neat, undiluted form in a temperature range of 30 to 300 ° C, preferably 75 to 180 ° C. The hydrogen fluoride partial pressure is 50 to 1500 mbar. Preferably 350 to 600 mbar. Typically, the fluorination reaction is carried out in a metal tube reactor.

The The resulting catalytically active solid material retains the amorphous X-ray structure and has a very high specific surface area and a distorted structure compared with the crystalline form of the corresponding metal fluoride on. This disorder is for the observed extremely high Lewis acidity of Lewis acid metals, as in the amorphous metal fluoride according to the present invention are responsible.

Next the use of the method according to the invention for the preparation of magnesium fluoride or aluminum fluoride sols and gels, the present technique especially for such Metals are used, which are selected from the group comprising Cr, Fe, V, Ga, Pb, Ca, Ba and Zn Processes more detailed herein for magnesium and aluminum, respectively also to corresponding fluorides of these metals applicable.

Furthermore It is within the scope of the present invention that the metal fluoride may also be a mixed metal fluoride.

The amorphous metal fluoride prepared according to the invention is X-ray amorphous. As used herein, the term X-ray amorphous means that the microcrystalline domains of the solid, ie, the amorphous metal fluoride, are less than 20 nm in size. A transmission electron microscopic study confirmed, at a magnification of 10 ⁷ , that the amorphous metal fluoride according to the present invention, such as AlF _{3, is} in the form of very small solid particles that are partially agglomerated to form larger units. Further scanning electron microscopic studies revealed a mesoporous surface of the amorphous metal fluoride according to the present invention. The peculiarities of the morphology and the pore structure of the amorphous metal fluoride according to the invention lead to a considerable increase of the catalytically active surface and thus of the catalytic activity.

BET measurements using N ₂ , as known in the art and determined, for example, with an ASAP2001 instrument (Micromeritics) at 77 K, give surface values of> 250 m ² / g. Solid-state NMR studies of the central Al atom can also be used to determine the proximity order on aluminum and differentiate between different Al species. The greatly disordered AlF ₃ lattice order is responsible for the X-ray amorphous state of the solid, ie, the amorphous metal fluoride of the present invention as well as the desired and intended increase in catalytic activity. The strongly disordered lattice structure of the amorphous metal fluoride according to the present invention is also confirmed by IR spectroscopic studies. The experimental evidence of increased Lewis acidity can be provided by pyridine adsorption and NH ₃ -TPD as described in the prior art.

The catalytically active metal fluorides according to the present invention are applicable to reactions where also metal fluorides of the prior art the technique can be used. About that can out the catalytically active metal fluorides are used for catalysis of halogen exchange reactions, the exchange reactions of chlorinated hydrocarbons, Chlorofluorocarbons and fluorocarbons particularly are preferred. Also can the catalytically active metal fluorides in any catalytic Reaction can be used where a Lewis acid catalyst is used. Other preferred reactions using the catalytic active metal fluorides of the present invention can be catalyzed the isomerization of haloperfluoroalkanes, the haloperfluoroalkanes preferably selected are selected from the group consisting of chlorine / bromine fluoroethanes and propanes, the isomerization of olefins, wherein the olefin isomerization preferably selected is selected from the group consisting of alkene-1 to alkene-2, for example Butene-1 to butene-2 isomerizations, in Friedel-Crafts acylation reaction catalysis, wherein the acylation reaction are preferably those selected from the Group selected are composed of benzoylation / acetylation of activated as well such as deactivated aromatic systems, as well as in Friedel-Crafts alkylation reactions, wherein the alkylation reactions are preferably selected from the group consisting of the alkylation of aromatic rings.

The amorphous metal fluoride powders obtained by the process can be pressed into transparent ceramics, for example for applications in the optical field. Methods for producing ceramics are known in the art and described, for example, in J. Lucas, F. Smektala, JL Adam, Fluorine in Optics, in J. Fluori Chem. 114 (2002), 113-118.

The sol state of the metal fluorides prepared according to the invention can be used to produce thin amorphous metal fluoride layers on different substrates, such as Si, SiO ₂ , metal or polymer material by dip coating, spin coating or other known methods. The corresponding methods are known in the art and described, for example, in CJ Brinker and GW Scherer, Sol-Gel Science, Academic Press, Boston 1990.

Example 1: Preparation of methanolic aluminum fluoride gel

Aluminum foil (0.27 g, 0.01 mol) was brought into contact with a very small amount of mercury (sphere of about 0.5 mm diameter). To the amalgamated aluminum, 7.5 ml of a 4.4 molar methanolic hydrofluoric acid solution (0.033 mol) were added in a plastic vessel and made up to 25 ml with anhydrous methanol. The reaction was stirred at room temperature; The aluminum dissolved during 48 h. The resulting colorless, slightly viscous liquid could be easily separated from the unreacted mercury ball. The white solid obtained after removal of methanol in vacuo at 70 ° C corresponded in its fluorine and carbon content and its behavior in the thermal analysis entirely the technical teaching of EP 04700458.5 prepared precursor molecule there, and by treatment with CCl ₂ F ₂ at a maximum of 280 ° C in the flow reactor to a HS-AlF ₃ (high surface aluminum fluoride) with the in EP 04700458.5 nachfluoriert described properties.

Example 2: Preparation of aluminum fluoride coatings

• a) Zur Erzeugung einer AlF₃-Schicht auf einer Si-Oberfläche wird die erhaltene Sol-Lösung mittels Spin-Coating (bei 5000 rpm) aufgetragen und 3 h bei 25°C und 1 h bei 300°C getrocknet. Die Oberfläche wurde durch Kraftfeld-Mikroskopie und Ellipsometrie charakterisiert, wobei eine Schichtdicke von 50-60 nm ermittelt wurde.
• b) Sphärische α-Al₂O₃ Pellets (o ca. 3 mm) werden mit dem solchermaßen erhaltenen AlF₃-Sol imprägniert. Nach dem Trocknen bei Temperaturen von 25-50°C werden die Pellets wie in EP 04700458.5 beschrieben in einem N₂-verdünnten CHClF₂-Strom bei Temperaturen von 25-280°C nachbehandelt. Der so erhaltene geträgerte AlF₃-Katalysator besteht gemäß gravimetrischer Analyse aus 95% α-Al₂O₃ und 5% AlF₃, und er zeigte in eine hohe katalytische Aktivität für CHClF₂-Dismutierung, vergleichbar der in EP 04700458.5 für HS-AlF₃ beschriebenen.
• c) Aus dem solchermaßen erhaltenen AlF₃-Sol, das durch die Formel AlF₃·n(CH₃OH) beschrieben werden kann, mit n ≈ 16, wird durch Erhitzen im Vakuum (120°C, 0,1 mbar, 6 h) das Lösungsmittel entfernt, wobei ein weißes Pulver von AlF₃ mit einem Kohlenstoffgehalt von 0,9% erhalten wird. Das so erhaltene Aluminiumfluorid ist Röntgen-amorph und weist eine spezifische Oberfläche von 252 m²/g auf.

5.4 g of Al powder (0.2 mol) are added with stirring to 75 mL of 16% HF / CH ₃ OH solution (0.6 mol). To complete the reaction, 30 mL of CH ₃ OH and 30 mg of HgCl _{2 are} added after 3 h. After further stirring and subsequent filtration, a clear sol-like solution of solvated AlF _{3 is} obtained which shows in the ¹⁹ F-NMR spectrum the characteristic peaks at -164 ppm and -174 ppm.

• a) To produce an AlF ₃ layer on a Si surface, the resulting sol solution is applied by spin coating (at 5000 rpm) and dried at 25 ° C for 3 h and at 300 ° C for 1 h. The surface was characterized by force field microscopy and ellipsometry, whereby a layer thickness of 50-60 nm was determined.
• b) Spherical α-Al ₂ O ₃ pellets (about 3 mm diameter) are impregnated with the AlF ₃ sol thus obtained. After drying at temperatures of 25-50 ° C, the pellets as in EP 04700458.5 aftertreated in an N ₂ -dissolved CHClF ₂ stream at temperatures of 25-280 ° C. According to gravimetric analysis, the supported AlF ₃ catalyst thus obtained consists of 95% α-Al ₂ O ₃ and 5% AlF ₃ , and showed high catalytic activity for CHClF ₂ dismutation, comparable to that in US Pat EP 04700458.5 for HS-AlF ₃ described.
• c) From the thus obtained AlF ₃ sol, which can be described by the formula AlF ₃ .n (CH ₃ OH), with n ≈ 16, by heating in vacuo (120 ° C, 0.1 mbar, 6 h ) The solvent is removed to give a white powder of AlF ₃ having a carbon content of 0.9%. The aluminum fluoride thus obtained is X-ray amorphous and has a specific surface area of 252 m ² / g.

The Release of methanol was also monitored quantitatively by thermal analysis, wherein a weight loss of the sample of 15.6% by thermogravimetry and differential thermogravimetry was detected. The thermal Effects were endothermic.

Example 3: Production of methanolic magnesium fluoride gel

In a plastic vessel, magnesium chips were mixed with 75 ml of a 2 molar methanolic hydrogen fluoride solution and stirred at room temperature. After 2 days, the gray sediment was decanted. From the colorless supernatant solution, after removal of the excess methanol in vacuo, a nearly white solid was obtained which had a specific surface area (BET / N ₂ ) of 348 m ² / g. Despite the large surface area, the sample showed clear, albeit broad, reflections of MgF ₂ in the X-ray powder diffraction gram.

Example 4: Preparation of barium fluoride

690 mg (5 mmol) of metallic barium were mixed with a methanolic HF solution in excess, based on the HF content, offset. Under gas evolution and formation of a dissolves milky sols the barium opens up. Concentrating the sol occurs white X-ray Amorphous Powder of barium fluoride. The reaction proceeds based on the used Barium quantitatively.

Example 5: Preparation of zinc fluoride

1.24 g of zinc powder (activated with a copper salt before use) were treated with a stoichiometric amount of HF in methanol, with the onset of gas evolution becoming a cloudy milky ge solution forms. After one day, the HF solution was supplemented. After completion of the reaction and separation of the solvent, a white amorphous powder of ZnF _{2 was} obtained. The X-ray diffractogram has very broad reflections attributable to zinc fluoride. The carbon content is 0.2%.

The features disclosed in the foregoing description, claims and drawings of the invention both individually and in any combination for the realization of Invention be essential in their various embodiments.

Claims (24)

Process for the preparation of a metal fluoride sol and a metal fluoride gel comprising the steps of: a) Provide a metal, b) providing a solution of hydrogen fluoride in one nonaqueous solvents, and c) reacting the metal with the solution of hydrogen fluoride in a non-aqueous Solvent for Formation of a metal fluoride sol. A method according to claim 1, characterized in that the metal is a metal of the second, third or fourth main group or a subgroup of the periodic table, wherein the redox potential of the metal in the respective solvent is more negative than that of H ₂ . Method according to claim 2, characterized in that that the metal is selected from the group consisting of magnesium, calcium, Strontium, barium, aluminum, zinc, lead, rare earths. Method according to claim 3, characterized that the metal is selected from the group consisting of magnesium and Aluminum includes. Method according to one of claims 1 to 4, characterized that the metal with the solution of hydrogen fluoride in a stoichiometric based on hydrogen fluoride relationship or with a surplus is reacted on hydrogen fluoride. Method according to one of claims 1 to 5, characterized that non-aqueous solvent an alcohol is selected is from the group comprising methanol, ethanol, propanol, isopropanol, Butanol, iso-butanol, tert-butanol, methoxyethanol, ethoxyethanol includes. Method according to one of claims 1 to 6, characterized that the alcohol contains up to 4% water. Method according to one of claims 1 to 5, characterized that non-aqueous solvent an ether or a ketone or a sulfoxide. Method according to one of claims 1 to 8, characterized that the reaction of step c) at room temperature and standard pressure he follows. Method according to one of claims 1 to 9, characterized that the metal fluoride sol or metal fluoride gel has a content Solvent of 50 mol% to 99.9 mol%, preferably from 70 mol% to 99 mol% having. Method according to one of claims 1 to 10, characterized that the metal is an alloy or mixture of two or more Metals is. A metal fluoride sol or metal fluoride gel, available after A method according to any one of claims 1 to 11. Method according to one of claims 1 to 11, characterized that it further comprises the step: d) Removal of the volatile Ingredients from the reaction product obtained in step c). Method according to claim 13, characterized in that that the volatile components are removed by a heat treatment become. Method according to claim 14, characterized in that that the heat treatment at a temperature of 30 to 500 ° C, preferably from 70 to 250 ° C he follows. A method according to claim 14 or 15, characterized in that the heat treatment is carried out in vacuo at a pressure of 800 to 10 ^-3 mbar, preferably from 100 to 10 ^-1 mbar. The method of any one of claims 13 to 16, wherein the method is a process for producing an amorphous metal fluoride. Amorphous metal fluoride, characterized that it is obtainable by a method according to any one of claims 13 to 17. A method for coating a surface, preferably for film coating a surface, comprising the steps of: a) providing a surface, b) providing a metal fluoride sol or metal fluoride gel c) coating the metal fluoride gel or metalflu ori- sols on a surface; and d) optionally removing the solvent from the sol or gel. Method according to claim 19, characterized that the metal fluoride sol or the metal fluoride gel by a Method according to one of the claims 1 to 11 or a metal fluoride sol or metal fluoride gel according to claim 12. Use of a metal fluoride sol or gel after Claim 12 for the production of a coating, preferably a protective coating, an antireflection coating or a catalytically active Layer on a suitable carrier. Use of a metal fluoride according to claim 18 for the Production of ceramics, preferably transparent ceramics. Use of a metal fluoride gel or metal fluoride sol according to claim 12 for the production of metal fluoride coated fibers or waveguides. An article comprising a metal fluoride sol or A metal fluoride gel according to any one of the preceding claims, wherein the item is selected from the group comprising glass panes, cathode ray tubes, liquid crystal displays, metal surfaces and lenses.