WO2009024312A2

WO2009024312A2 - Method for the production and stabilization of functional metal nanoparticles in ionic liquids

Info

Publication number: WO2009024312A2
Application number: PCT/EP2008/006768
Authority: WO
Inventors: Christoph Janiak; Engelbert Redel; Marco Klingele; Thomas Schubert; Tom Beyersdorff
Original assignee: Albert-Ludwigs-Universität Freiburg; Iolitec Ionic Liquids Technologies Gmbh & Co. Kg
Priority date: 2007-08-17
Filing date: 2008-08-18
Publication date: 2009-02-26
Also published as: DE102007038879A1; WO2009024312A3

Abstract

The present invention relates to a method for the reductive production and stabilization of functional metal nanoparticles under mild conditions in ionic liquids from the associated soluble salt sources by using elemental hydrogen in the presence of a proton catcher, allowing to adjust the particle size and the size distribution thereof by the appropriate choice of the used ionic liquid.

Description

Process for the preparation and stabilization of functional metal nanoparticles in ionic liquids

The present invention describes a process for the reductive production and stabilization of functional metal nanoparticles in ionic liquids using elemental hydrogen, which makes it possible to adjust the particle size and the size distribution by suitable choice of the ionic liquid used.

Nanomaterials, ie materials with a particle size in the nanometer range, represent a new class of materials, which is of increasing importance for more and more technical areas. In most cases, nanomaterials are of inorganic nature, e.g. Metals, metal oxides, metal phosphates, metal alloys or non-metals, but there are also organic nanomaterials. Above all, nanoparticles are characterized by the fact that they have a huge surface area relative to their volume, which means that they have far more atoms on their surface compared to materials with larger particle sizes. Herein often the special properties of nanomaterials are founded, the old known materials improved or completely new properties and thus can open up new applications [G. Schmid, Nanoparticles: From Theory to Application, Wiley-VCH, Weinheim, 2003, pages 1-434].

Metal nanoparticles are already widely used in various fields of chemistry and materials science. As a component of hybrid materials, they can impart new properties to the material or reinforce existing physical or mechanical properties, eg electrical conductivity, thermal conductivity or resistance to breakage, while at the same time reducing weight. Nanoscale metal powders can be sintered without pressure and at lower temperatures. The resulting materials are characterized by greater compactness and improved mechanical properties. Nanoscale silver gives workpieces antimicrobial properties when applied in the form of a coating or added as a dopant to the material. This property is used in particular Area of sanitary facilities, used in the food and hygiene sector, for example, in coating dispensers for hospitals, housing of medical equipment or in refrigerators. Furthermore, nanomaterials can often be used as efficient catalysts for a wide variety of processes [D. Astruc, Nanoparticles and Catalysis, Wiley-VCH, Weinheim, 2007, pp. 1-634]. An industrially very important oxidation process is, for example, the conversion of olefins into epoxides [K. Weissermel, HJ Arpe, Industrial Organic Chemistry, 4th Edition, Wiley-VCH, Weinheim, 2003, pp. 145-192 and 267-312; BK Hodnett, Heterogeneous Catalytic Oxidation, Wiley-VCH, Weinheim, 2000, pp. 160-188]. Oxidative petroleum products, such as acrylates, are important monomers or intermediates for the chemical and pharmaceutical industries. Catalytically active, stabilized metal nanoparticles, in particular silver manoparticles, can also serve valuable purposes for their production and lead to more efficient processes.

Several processes are already available today for the preparation of metal nanoparticles, which are briefly explained below [C. N.R. Rao, A.M., A. Cheetham, The Chemistry of Nanomaterials: Synthesis, Properties and Applications, Wiley-VCH, Weinheim, 2004, pp. 1-741; B. Bhushan, Springer Handbook of Nanotechnology, 2nd edition, Springer, Berlin, 2007, pages 1-1916].

(1) Steam condensation method:

In steam condensation processes, eg CVD or PVD, the metals are evaporated in vacuo and separated by subsequent quenching in nanoscale powders. If the quenching is carried out in a protective gas atmosphere, metal nanoparticles are obtained. In the presence of oxygen, on the other hand, nanoscale metal oxides are produced; in the presence of nitrogen, metal nitride nanoparticles can be produced. In a special form of this process, CVD precursors, ie metal compounds, are thermally decomposed in the gas phase to form nanoparticles. These gas phase methods are relatively rarely used for the production of metal nanoparticles. Their biggest drawbacks include the very high investment requirements and the ongoing process costs caused by vacuum generation and metal evaporation. In addition, the resulting particle sizes and size distributions are difficult to control by the choice of process conditions. (2) milling method:

Another production method for nanoparticles is the milling process. Here, the comminution of microscale materials in special nanomills. Since grinding at the nanometer level is very energy-intensive, this method has proved uneconomical for large-scale industry. In addition, contamination of the nanopowders may occur due to the grinding materials used.

(3) Wet chemical methods: By chemical methods, e.g. the sol-gel process or the wet-chemical reduction, the shape and size of the nanoparticles can be much better controlled. The choice of a suitable surfactant enables the preparation of many metal and metal oxide nanoparticles in precipitation reactions. The biggest disadvantage of these methods is that impurities from the reaction solution, e.g. unreacted starting materials or reagents, can find in the nanopowders and therefore need to be cleaned and dried consuming and under controlled conditions. As substrates, metal halides (preferably chlorides) are used in most cases for cost reasons; The price of the much more suitable alkoxides leads to significantly higher costs and would in many cases make the process uneconomical. In addition, as reaction media are often used toxic, flammable and volatile organic solvents, which are usually difficult or impossible to reuse due to the entry of the reagents. The unavoidable use of surfactants for stabilization also occupies much of the surface of the nanoparticles of stabilizer molecules, greatly reducing the useful surface area of the particles for further use as a catalyst or for subsequent functionalization, and the metal nanoparticles prepared in this manner for these purposes often unusable.

(4) Electrochemical methods:

Compared to the aforementioned methods of nanoparticle production, electrochemical processes are much more efficient and reliable. By way of electrochemical reduction, both metal and - A -

Metal oxide nanoparticles - the latter by oxidation of the metal nanoparticles formed by the reduction process by an added oxidizing agent or atmospheric oxygen in situ - from the respective metals or metal salts in high purity produce. The findings from the metal industry on the electrorefining of metals are used here. Furthermore, electrochemical processes are characterized in particular in comparison to the steam condensation process by much higher efficiency. However, in the electrochemical production of nanoparticles, it is still difficult to control the resulting particle sizes and size distributions by appropriate choice of process parameters. A further disadvantage of the electrochemical processes is that they hitherto only permit the production of smaller amounts of nanopowders. In addition, organic solvents and surface-blocking stabilizers are also frequently used here.

The aim of the present invention is therefore to provide a process for the preparation and stabilization of functional metal nanoparticles that avoids the disadvantages of the above-mentioned processes by the use of ionic liquids as the reaction medium and elemental hydrogen as the reducing agent. That the generation of nanocrystalline deposits on a substrate is advantageously possible by electrochemical reduction from ionic liquids has already been shown elsewhere [M. Bukowski, F. Endres, R. Hempelmann, H. Natter, Patent Publication DE10108893, 2002]. The possibility of producing catalytically active iridium and rhodium nanoparticles by the reduction of corresponding metal salts with hydrogen in ionic liquids is known [G. S. Fonseca, A.P. Umpierre, P.F.P. Fichtner, S.R. Teixeira, J. Dupont, Chem. Eur. J. 2003, 9, 3263-3269]. The stabilization of transition metal nanoparticles by ionic liquids on the core-shell principle and the resulting possibility of producing functional, catalytically active metal nanoparticles has also been described [M. Antonietti, D. Kuang, B. Smarly, Y. Zhou, Angew. Chem. 2004, 116, 5096-5100; D. Astruc, F. Lu, J.R. Aranzaes, Angew. Chem. 2005, 117, 8062-8083].

Ionic liquids are defined liquid compounds exclusively composed of ions, which differ from classic molten salts, especially due to the unusually low temperatures (preferably <100 ⁰ C) differ, in which they are present in the liquid state of matter [T. Welton, Chem. Rev. 1999, 99, 2071-2083; P. Wasserscheid, W. Keim, Angew. Chem. 2000, 112, 3926-3945; P. Wasserscheid, T. Welton, Lonic Liquids in Synthesis, Wiley-VCH, Weinheim, 2003, pp. 1-364]. In addition, ionic liquids have negligible vapor pressure, high thermal, chemical and electrochemical stability, and have versatile miscibility with water and organic solvents, which can be used to advantage in productions or product recovery or catalyst recovery.

It has now been found that functional, stable metal nanoparticles with a narrow size distribution can advantageously be prepared by reduction of suitable metal salts with elemental hydrogen in ionic liquids, preferably in the presence of a nitrogen base serving as proton scavenger, and that the size of the metal nanoparticles formed in the reduction process can be reduced by suitable Choice of ionic liquid, ie through the use of anions and cations of a certain size. The reduction is carried out in a stainless steel autoclave at elevated temperature and under hydrogen pressure. Typically, a high purity metal salt is dissolved at room temperature in a suitable ionic liquid. A sufficient solubility of the metal salt in the ionic liquid used is a prerequisite for the applicability of the present method. Subsequently, the solution is transferred to the autoclave and dried under high vacuum. Thereafter, the autoclave is filled directly with hydrogen and the reaction mixture is heated. After cooling, the nanoparticles formed can be separated off from the ionic liquid by centrifuging, so that the ionic liquid, if appropriate after an intermediate purification step, can be reused for further reactions. Alternatively, the obtained nanoparticle dispersion can also be used directly. The process will be explained below using the example of the preparation of silver nanoparticles.

Some silver (I) salts, for example silver (I) tetrafluoroborate (AgBF ₄ ), silver (I) hexafluorophosphate (AgPF ₆ ) or silver (I) trifluoromethanesulfonate (AgOTf), can be dissolved in ionic liquids, for example 1- butyl-3-methyl-imidazolium tetrafluoroborate (BMIM-BF ₄ ), 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIM-PF ₆ ), 1-butyl-3-methyl-imidazolium trifluoromethanesulfonate (BMIM-OTf) or butyl-trimethyl-ammonium-bis ( trifluoromethylsulfonyl) imide (Ni, i, ^ ₄ -NTf ₂ ), dissolve and reduce by hydrogen to silver nanoparticles. If the acid formed during the reduction from hydrogen and the anion of the salt used, for example tetrafluoroboric acid (HBF ₄ ), hexafluorophosphoric acid (HPF ₆ ), trifluoromethanesulfonic acid (TfOH) or bis (trifluoromethylsulfonyl) imide (HNTf ₂ ), not by an added proton scavenger - preferably bound to the ionic liquid used nitrogen base - bound, the uniform particle formation is inhibited because the stabilizing core-shell structure of nanoparticles and ionic liquid is disturbed. There is an agglomeration of the formed nanoparticles, and a very broad size distribution results, s. FIG. 1

On the other hand, if the reduction is carried out in the presence of a proton scavenger, the agglomeration of the nanoparticles formed is prevented. Dispersions of finely divided, almost monodisperse nanoparticles in the ionic liquid are obtained. Figure 2. It shows:

1: TEM image of Ag nanoparticles prepared in BMIM-OTf from AgOTf without addition of a proton scavenger

FIG. 2: TEM image of Ag nanoparticles prepared in BMIM-BF ₄ from AgBF ₄ with addition of 1-butylimidazole as proton scavenger

3: Overview scheme for the synthesis of metal nanoparticles by reduction of metal salts with hydrogen in ionic liquids using the example of Ag nanoparticles prepared from AgOTf and BMIM-OTf with addition of 1-butylimidazole as proton scavenger.

FIG. 4: Plot of the anion size (molar volumes) of the ionic liquid used against the particle size of the resulting Ag nanoparticles. Particularly suitable as proton scavengers are those materials which form cations by the uptake of protons whose molar volume corresponds approximately to the size of the cations of the ionic liquid used. Particularly preferred here is the ionic liquid underlying nitrogen base used. This can be released again after the reaction by neutralization, for example with sodium hydroxide, separated from the ionic liquid and reused, s. Figur.3.

According to the core-shell principle, the stabilization of nanoparticles in ionic liquids takes place through the formation of alternating layers

Anions and cations around the nucleus. The thickness of the shell is dependent on the molar volume of the ions of the ionic liquid used. It is generally believed that the first ionic layer directly surrounding the nanoparticles is composed of anions. It follows that the anions of the ionic liquid have the greatest influence on the size and stability of the ionic liquid

Nanoparticles should have.

Table 1 :

Mean particle size

Used molar volume

Ionic liquid of the Ag nanoparticles Ag-SaIz of the anion [nm ³ ] [nm]

BMIM-BF ₄ AgBF ₄ 0.073 ± 0.009 2.80 ± 0.78

BMIM-PF ₆ AgPF ₆ 0.109 ± 0.008 4.36 ± 1.25

BMIM-OTf AgOTf 0.131 ± 0.015 7.65 ± 4.50 ( ^* )

Ni _1I1 M-NTf ₂ AgOTf 0.232 ± 0.015 26.08 ± 6.39 (*) = in the absence of a proton scavenger

In fact, it has now been found that, according to the present method, different particle sizes can be set depending on the anions of the ionic liquids used, with a linear relationship between the molar volume of the anion and the mean particle size of the nanoparticles obtained, as in Table 1 and FIG shown. Table 1 shows the dependence of the particle size of the resulting Ag nanoparticles on the anion sizes (molar volumes) of the ionic liquid used. A variation of the cation of the ionic liquid used has only a minor influence on the particle size, but can additionally be used as a possibility for finely adjusting the particle size. The metal nanoparticles produced by the present process show size distributions ≤30%.

The essential advantages of the present invention are therefore that by using ionic liquids as the reaction medium metal nanoparticles can be produced in a new economical, energy-efficient and environmentally friendly process without the use of toxic, flammable, and volatile solvents. Furthermore, no separate surface-active substances for stabilizing the nanoparticles are needed, which occupy the usable surface of the resulting nanoparticles and in particular reduce their catalytic activity. Thus, the mere presence of the ionic liquid and the associated strong electrostatic stabilization can be used to produce "naked" metal nanoparticles in a gentle manner.

Reducing agent also makes it possible to produce nanoparticles in high purity. Furthermore, the process described here is in principle also suitable for the production and isolation of metal nanoparticles on a larger scale. The initial dispersions of nanoparticles in ionic liquids can also be used directly in catalytic processes. Another important advantage of the present invention results from the controllability of the particle size and size distribution by suitable choice of the ionic liquid used, which in turn results in the possibility of controllability of the catalytic activity of the metal nanoparticles.

G

The present method is suitable in principle for the production of nanoparticles of all metals which form salts soluble in ionic liquids and whose salts can be reduced with hydrogen to the corresponding metal. Without limiting the generality, nanoparticles of the transition metals, ie metals of groups 3 to 12 of the periodic table, can preferably be prepared by the process described here. Particularly preferred metals are silver (Ag), copper (Cu), gold (Au) ₁ nickel (Ni), palladium (Pd), platinum (Pt), Cobalt (Co), rhodium (Rh), iridium (Ir), iron (Fe), ruthenium (Ru), osmium (Os), zinc (Zn), cadmium (Cd), manganese (Mn), rhenium (Re), Chromium (Cr), molybdenum (Mo), tungsten (W), vanadium, niobium (Nb), tantalum (Ta), ₁ titanium (Ti), zirconium (Zr), hafnium (Hf), scandium (Sc) and yttrium (Y ).

Ionic liquids in the sense of the present invention are preferably salts of the general formula ## STR5 ## which are composed of cations [Q ^{n +} ] and anions [Z "^1" ]

[Q ^{n +} ] _m [Z ^ _n

with n = m or n ≠ m and 1 ≦ n ≦ 4 and 1 ≦ m ≦ 4 including mixtures of several such salts having a melting point <180 ° C, preferably <120 ° C and most preferably <1 OfJ ⁰ C, wherein those ionic liquids are particularly preferred in which n = m = 1.

For example, without limitation of generality, suitable cations [Q ^{n +} ] are

(I) Imidazolium cations of the general structure:

(II) Ammonium cations of the general structure:

R2

R3-N-R1 R4

(III) pyrrolidinium cations of the general structure:

(IV) piperidinium cations of the general structure:

(V) pyridinium cations of the general structure:

(VI) Morpholinium cations of the general structure:

(VII) guanidinium cations of the general structure:

(VII) Benzotriazolium cations of the general structure:

or (IX) Quinolinium cations of the general structure:

(X) isoquinolinium cations of the general structure:

(XI) pyrazolium cations of the general structure:

(XII) 1, 4-diazabicyclo [2.2.2] octane-1-ium cations of the general structure:

(XIII) 1, 2,4-triazolium cations of the general structure:

(XIV) pyridazinium cations of the general structure:

(XV) pyrimidinium cations of the general structure:

(XVI) pyrazinium cations of the general structure:

(XVII) 1, 3,5'-triazinium cations of the general structure:

R3

R4 ^ ^ N R2 R1

(XVIII) 1, 2,3-triazolium cations of the general structure:

(XIX) piperazinium cations of the general structure:

(XX) oxazolium cations of the general structure:

(XXI) oxazolidinium cations of the general structure:

(XXII) Thiazolium cations of the general structure:

(XXIII) Quinoxalinium cations of the general structure:

(XXIV) benzimidazolium cations of the general structure:

(XXV) imidazolidinium cations of the general structure:

(XXVI) indolinium cations of the general structure:

(XXVII) Thiomoφholium cations of the general structure:

In the above-mentioned general structures (I) to (XXVII):

The radicals R 1 to R 13 independently of one another represent hydrogen or a monovalent carbon-containing organic, saturated or unsaturated, linear or branched, acyclic or cyclic, aliphatic, aromatic or araliphatic, unsubstituted, partially or completely halogenated or by 1 to 5 hetero atoms or functional Groups are interrupted or substituted radicals having from 1 to 30 carbon atoms;

• two adjacent radicals from the series R1 to R13 together also represent a divalent carbon-containing organic, saturated or unsaturated, linear or branched, acyclic or cyclic, aliphatic, aromatic or araliphatic, unsubstituted, partially or completely halogenated or by 1 to 5 heteroatoms or functional groups are interrupted or substituted radicals having 1 to 30 carbon atoms.

Particularly preferred heteroatoms which can occur in the radicals R 1 to R 13 are oxygen, sulfur, selenium, tellurium, nitrogen, phosphorus and silicon. In principle, the radicals R 1 to R 13 can be bonded either via a carbon atom or a heteroatom.

Preferred functional groups which can occur in the radicals R 1 to R 13 are, in particular, hydroxyl, carbonyl, carboxyl, carboxamido, amino and cyano groups. As halogens its called fluorine, chlorine, bromine and iodine.

Particularly preferred cations of group (I) are

• the asymmetric 1, 3-dialkylated, non-protic imidazolium cations. 1-ethyl-3-methyl-imidazolium, 1-methyl-3-propyl-imidazolium, 1-isopropyl-3-methyl-imidazolium, 1-butyl-3-methyl-imidazolium, 1-methyl-3-pentyl imidazolium, 1-hexyl-3-methyl-imidazolium, i-heptyl-3-methyl-imidazolium, 1-methyl-3-octyl-imidazolium, 1-methyl-3-nonyl-imidazolium, 1-decyl-3-methyl imidazolium, 1-methyl-3-undecyl-imidazolium _t 1-dodecyl-3-methyl-imidazolium, 1-methyl-3-tridecyl-imidazolium, 1-methyl-3-tetradecyl-imidazolium, 1-methyl-3-pentadecyl imidazolium, 1-hexadecyl-3-methyl-imidazolium, 1-methyl-3-octadecyl-imidazolium and 1-eicosyl-3-methyl-imidazolium, as well

1-butyl-3-ethyl-imidazolium, 1-ethyl-3-hexyl-imidazolium, 1-ethyl-3-octyl-imidazolium, 1-decyl-3-ethyl-imidazolium, i-dodecyl-3-ethyl-imidazolium, 1-ethyl-3-tetradecyl-imidazolium, 1-ethyl-3-hexadecyl-imidazolium, 1-ethyl-3-octadecyl-imidazolium, 1-butyl-3-hexyl-imidazolium, 1-butyl-3-octyl-imidazolium, i-butyl-3-decyl-imidazolium, 1-butyl-3-dodecyl-imidazolium, 1-butyl-3-tetradecyl-imidazolium, 1-butyl-3-hexadecyl-imidazolium, 1-butyl-3-octadecyl-imidazolium, 1-hexyl-3-octyl-imidazolium, 1-decyl-3-hexyl-imidazolium, 1-dodecyl-3-hexyl-imidazolium, i-hexyl-3-tetradecyl-imidazolium,

1-hexadecyl-3-hexyl-imidazolium, 1-hexyl-S-octadecyl-imidazolium, 1-decyl-3-octyl-imidazolium, 1-dodecyl-3-octyl-imidazolium, 1-octyl-3-tetradecyl-imidazolium, 1-hexadecyl-3-octyl-imidazolium, 1-octadecyl-S-octyl-imidazolium, i-decyl-3-dodecyl-imidazolium, i-decyl-3-tetradecyl-imidazolium, 1-decyl-3-hexadecyl-imidazolium, i-decyl-S-octadecylimidazolium, 1-dodecyl-3-tetradecylimidazolium, 1-dodecyl-S-hexadecylimidazolium, 1-dodecyl-3-octadecylimidazolium, 1-hexadecyl-S-tetradecylimidazolium, 1-octadecyl-3-tetradecyl-imidazolium and 1-hexadecyl-S-octadecyl-imidazolium;

The symmetrically 1,3-dialkylated, non-protic imidazolium cations: 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1,3-dipropylimidazolium,

1,3-diisopropylimidazolium, 1,3-dibutylimidazolium, 1,3-dipentylimidazolium, 1,3-dihexylimidazolium, 1,3-diheptylimidazolium, 1,3-dioctylimidazolium, 1, 3-dinonylimidazolium, 1, 3-didecylimidazolium, 1, 3-diundecylimidazolium, 1, 3-didodecylimidazolium, 1,3-ditridecylimidazolium, 1, 3-ditetradecylimidazolium, 1, 3 Dipentadecylimidazolium, 1,3-dihexadecylimidazolium, 1, 3

Dioctadecylimidazolium and 1,3-dieicosylimidazolium;

• the 1,3,3-trialkylated, non-protic imidazolium cations:

1, 2,3-trimethyl-imidazolium, 1-ethyl-2,3-dimethyl-imidazolium, 1, 2-dimethyl-3-propyl-imidazolium, 1-isopropyl-2,3-dimethyl-imidazolium, 1-butyl 2,3-dimethyl- imidazolium, 1, 2-dimethyl-3-pentylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1-heptyl-2,3-dimethylimidazolium, 1, 2-dimethyl-3-octylimidazolium, 1, 2-dimethyl-3-nonylimidazolium, 1-decyl-2,3-dimethylimidazolium, 1, 2-dimethyl-3-undecylimidazolium, 1-dodecyl-2,3-dimethylimidazolium, 1, 2-Dimethyl-3-tridecyl-imidazolium, 1, 2-dimethyl-3-tetradecyl-imidazolium, 1, 2-dimethyl-3-pentadecyl-imidazolium, 1-hexadecyl-2,3-dimethyl-imidazolium, 1'-dimethyl -S-octadecylimidazolium and 1-eicosyl-2,3-dimethylimidazolium and 1,3-diethyl-2-methylimidazolium, I, S-dibutyl-methylimidazolium, 1, 3

Dihexyl-2-methyl-imidazolium, 2-methyl-1,3-dioctylimidazolium, 1,3-didecyl-2-methyl-imidazolium, 1,3-didodecyl-2-methyl-imidazolium, 2-methyl-1, 3-ditetradecylimidazolium, 1, 3-dihexadecyl-2-methylimidazolium, 2-methyl-1,3-dioctadecylimidazolium, 1, 2-diethyl-3-methylimidazolium and 1,2,3-triethyl imidazolium;

The 1, 3,4,5-tetraalkylated, non-protic imidazolium cations:

1, 3,4,5-tetramethylimidazolium, 1-ethyl-3,4,5-trimethylimidazolium, 1-butyl-3,4,5-trimethylimidazolium, 1-hexyl-3,4,5- trimethyl-imidazolium, 1, 4,5-trimethyl-3-octyl-imidazolium, 1-decyl-3,4,5-trimethyl-imidazolium, 1 -dodecyl-3,4,5-trimethyl-imidazolium, 1, 4, 5-trimethyl-3-tetradecylimidazolium, 1-

Hexadecyl-3,4,5-trimethylimidazolium and 1, 4,5-trimethyl-3-octadecylimidazolium;

• the 1-alkylated, protic imidazolium cations:

1-methyl-imidazolium, 1-ethyl-imidazolium, 1-propyl-imidazolium, 1-isopropyl-imidazolium, 1-butyl-imidazolium, 1-pentyl-imidazolium, 1-hexyl-imidazolium, 1

Heptylimidazolium, 1-octylimidazolium, 1-nonylimidazolium, 1-decylimidazolium, 1-undecylimidazolium, 1-dodecylimidazolium, 1-tridecylimidazolium, 1-tetradecylimidazolium, 1-pentadecyl imidazolium, 1-hexadecyl-imidazolium, 1-octadecyl-imidazolium and 1-eicosyl-imidazolium; • the 1,2-dialkylated protic imidazolium cations:

1, 2-dimethyl-imidazolium, 1-ethyl-2-methyl-imidazolium, 1-methyl-2-propyl-imidazolium, 1-isopropyl-2-methyl-imidazolium, 1-butyl-2-methyl-imidazolium, 1 - Methyl 2-pentylimidazolium, 1-hexyl-2-methylimidazolium, 1-heptyl-2-methylimidazolium, 1-methyl-2-octylimidazolium, 1-methyl-2-nonylol imidazolium, i-decyl-2-methyl-imidazolium, 1-methyl-2-undecyl-imidazolium, 1-dodecyl-2-methyl-imidazolium, 1-methyl-2-tridecyl-imidazolium, 1-methyl-2-tetradecyl imidazolium, 1-methyl-2-pentadecyl-imidazolium, 1-hexadecyl-2-methyl-imidazlium, i-methyl-2-octadecyl-imidazolium and 1-eicosyl-2-methylimidazolium;

The 1, 3 and 1, 2,3-substituted, non-protic imidazolium cations:

1-methyl-3-vinyl-imidazolium, 1-allyl-3-methyl-imidazolium, 1-benzyl-3-methyl-imidazolium, 1- (2-hydroxyethyl) -3-methyl-imidazolium, 1- (2-hydroxyethyl ) -2,3-dimethylimidazolium, 1- (2-methoxyethyl) -3-methylimidazolium and 1- (2-methoxyethyl) -2,3-dimethylimidazolium.

Particularly preferred cations of group (II) are

• the quaternary, non-protic ammonium cations:

Tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetraisopropylammonium, tetrabutylammonium, tetrapentylammonium,

Tetrahexylammonium, tetraheptylammonium, tetraoctylammonium, tetranonylammonium, tetradecylammonium, ethyltrimethylammonium, trimethylpropylammonium, isopropyltrimethylammonium, butyltrimethylammonium, trimethylpentylammonium, Hexyl-trimethyl-ammonium, heptyl-trimethyl-ammonium, trimethyl-octyl-ammonium, trimethyl-nonyl-ammonium,

Decyl-trimethyl-ammonium, dodecyl-trimethyl-ammonium, trimethyl-tetradecyl-ammonium, hexadecyl-trimethyl-ammonium, trimethyl-octadecyl-ammonium, triethyl-methyl-ammonium, triethyl-propyl-ammonium, triethyl-isopropyl-ammonium, butyl- triethylammonium, triethyl-pentyl-ammonium, triethyl-hexyl-ammonium, triethyl-heptyl-ammonium, triethyl-octyl-ammonium, triethyl-nonyl-ammonium, decyl-triethyl-ammonium, dodecyl-triethyl-ammonium, triethyl-tetradecyl- ammonium, triethyl-hexadecyl-ammonium, triethyl-octadecyl-ammonium, tripropyl-undecyl-ammonium, tributyl-methyl-ammonium, tributyl-ethyl-ammonium, tributyl-propyl-ammonium, tributyl-isopropyl-ammonium, tributyl-pentyl-ammonium, tributyl-hexyl-ammonium,

Tributyl heptyl ammonium, tributyl octyl ammonium, tributyl nonyl ammonium, tributyl decyl ammonium, tributyl dodecyl ammonium, tributyl tetradecyl ammonium, tributyl hexadecyl ammonium, tributyl octadecyl ammonium, trihexyl methyl ammonium, ethyl trihexyl ammonium, trihexyl propyl ammonium, trihexylisopropylammonium, butyltrihexylammonium, methyltrioctylammonium, ethyltrioctylammonium, trioctylpropylammonium, isopropyltrioctylammonium, butyltrioctylammonium, diethyldimethylammonium, Dimethyl-dipropyl-ammonium, diisopropyl-dimethyl-ammonium, dimethyl-dinonyl-ammonium, didodecyl-dimethyl-ammonium, diethyl-dipropyl-ammonium, diethyl-diisopropyl-ammonium, dibutyl-diethyl-ammonium, diethyl-dihexyl-ammonium, diethyl- diheptyl ammonium, diethyl dioctyl ammonium, dibutyl dihexyl ammonium, diheptyl dipropyl ammonium, 2-hydroxyethyl trimethyl ammonium (choline) and tris (2-hydroxyethyl) methyl ammonium; • the tertiary, protic ammonium cations:

Trimethylammonium, triethylammonium, tripropylammonium, triisopopylammonium, tributylammonium, tripentylammonium, trihexylammonium, triheptylammonium, trioctylammonium, diethylmethylammonium and tris (2-hydroxyethyl) - ammon iu m; • the secondary, protic ammonium cations:

Dimethyl ammonium, diethyl ammonium, dipropyl ammonium, diisopropyl ammonium, dibutyl ammonium, dipentyl ammonium, dihexyl ammonium, diheptyl ammonium, dioctyl ammonium, dinonyl ammonium, didecyl ammonium, didodecyl ammonium and bis ( 2-hydroxyethyl) ammonium; • the primary, protic ammonium cations:

Methyl ammonium, ethyl ammonium, propyl ammonium, isopropyl ammonium, butyl ammonium, pentyl ammonium, hexyl ammonium, heptyl ammonium, octyl ammonium, nonyl ammonium, decyl ammonium, dodecyl ammonium, tetradecyl ammonium ammonium, hexadecylammonium, octadecylammonium and 2-hydroxyethylammonium.

Particularly preferred cations of group (III) are:

1, 1-dimethylpyrrolidinium, 1-ethyl-1-methylpyrrolidinium, 1-methyl-1-propylpyrrolidinium, 1-butyl-1-methyl-pyrrolidinium, 1-hexyl-1-methylpyrrolidinium, 1 Methyl 1-octyl-pyrrolidinium, 1, 1-diethyl-pyrrolidinium, 1-ethyl-1-propyl-pyrrolidinium, 1-ethyl-1-butyl-pyrrolidinium, 1-ethyl-1-hexyl-pyrrolidinium, 1-ethyl 1-octyl-pyrrolidinium, 1, 1-dipropyl-pyrrolidinium, 1, 1-dibutyl-pyrrolidinium, 1, 1-dihexyl-pyrrolidinium and 1, 1-dioctyl-pyrrolidinium. Particularly preferred cations of group (IV) are:

1, 1-Dimethyl-piperidinium, 1-ethyl-1-methyl-piperidinium, 1-methyl-1-propyl-piperidinium, 1-butyl-1-methyl-piperidinium, 1-hexyl-1-methyl-piperidinium, 1 Methyl 1-octyl-piperidinium, 1, 1-diethyl-piperidinium, 1-ethyl-1-propyl-piperidinium, 1-ethyl-1-butyl-piperidinium, 1-ethyl-1-hexyl-piperidinium, 1-ethyl-

1-octyl-piperidinium, 1, 1-dipropyl-piperidinium, 1, 1-dibutyl-piperidinium, 1, 1-dihexyl-piperidinium and 1, 1-dioctyl-piperidinium.

Particularly preferred cations of group (V) are the 1-alkylated pyridinium cations:

1-methylpyridinium, 1-ethylpyridinium, 1-propylpyridinium, 1-butylpyridinium, 1-pentylpyridinium, 1-hexylpyridinium, 1-octylpyridinium, 1-decylpyridinium, 1 Dodecylpyridinium, 1-tetradecylpyridinium, 1-hexadecylpyridinium and 1-octadecylpyridinium; • the 1, 2-dialkylated pyridinium cations:. , .

1, 2-Dimethyl-pyridinium, 1-ethyl-2-methyl-pyridinium, 2-methyl-1-propyl-pyridinium, 1-butyl-2-methyl-pyridinium, 2-methyl-1-pentyl-pyridinium, 1 Hexyl 2-methyl-pyridinium, 2-methyl-1-octylpyridinium, i-decyl-2-methylpyridinium, 1-dodecyl-2-methyl-pyridinium, 2-methyl-1-tetradecylpyridinium, 1 - Hexadecyl-2-methyl-pyridinium and 2-methyl-1-octadecyl-pyridinium as well

1, 2-diethyl-pyridinium, 2-ethyl-1-propyl-pyridinium, 1-butyl-2-ethyl-pyridinium, 2-ethyl-1-pentyl-pyridinium, 2-ethyl-1-hexyl-pyridinium, 2- Ethyl 1-octylpyridinium, 1-decyl-2-ethyl-pyridinium, 1-dodecyl-2-ethyl-pyridinium, 2-ethyl-1-tetradecyl-pyridinium, 2-ethyl-1-hexadecylpyridinium and Ethyl 1-octadecylpyridinium; The 1,3-dialkylated pyridinium cations:

1,3-Dimethyl-pyridinium, 1-ethyl-3-methyl-pyridinium, 3-methyl-1-propyl-pyridinium, 1-butyl-3-methyl-pyridinium, 3-methyl-1-pentyl-pyridinium, 1 Hexyl-3-methylpyridinium, 3-methyl-1-octylpyridinium, i-decyl-3-methylpyridinium,

1 -dodecyl-3-methyl-pyridinium, 3-methyl-1-tetradecyl-pyridinium, 1-hexadecyl-3-methyl-pyridinium and 3-methyl-1-octadecyl-pyridinium, and 1, 3-diethyl-pyridinium, 3-ethyl-1-propyl-pyridinium, 1-butyl-3-ethyl-pyridinium, 3-ethyl-1-pentyl-pyridinium, 3-ethyl-1-hexyl-pyridinium, 3 Ethyl 1-octylpyridinium, i-decyl-3-ethyl-pyridinium, 1-dodecyl-3-ethylpyridinium, _f- 3-ethyl-1-tetradecyl-pyridinium, 3-ethyl-1-hexadecyl-pyridinium, and Ethyl 1-octadecylpyridinium;

The 1,4-dialkylated pyridinium cations:

1, 4-dimethylpyridinium, 1-ethyl-4-methylpyridinium, 4-methyl-1-propylpyridinium, 1-butyl-4-methyl-pyridinium, 4-methyl-1-pentyl-pyridinium, 1 Hexyl 4-methylpyridinium, 4-methyl-1-octylpyridinium, 1-decyl-4-methyl-pyridinium, 1-dodecyl-4-methylpyridinium, 4-methyl-1-tetradecyl-pyridinium, 1 hexadecyl

4-methylpyridinium and 4-methyl-1-octadecylpyridinium;

The 1,3,5-trialkylated pyridinium cations:

1, 3,5-trimethyl-pyridinium, 1-ethyl-3,5-dimethyl-pyridinium, 3,5-dimethyl-1-propyl-pyridinium, 1-butyl-3,5-dimethyl-pyridinium, 3,5- Dimethyl-1-pentyl-pyridinium, 1-hexyl-3,5-dimethyl-pyridinium, 3,5-dimethyl-1-octyl-pyridinium, 1

Decyl-3,5-dimethyl-pyridinium, 1-dodecyl-3,5-dimethyl-pyridinium, 3,5-dimethyl-1-tetradecyl-pyridinium, 1-hexadecyl-3,5-dimethyl-pyridinium and 3,5- Dimethyl 1-octadecyl-pyridinium.

Particularly preferred cations of group (VI) are:

4,4-dimethyl-morpholinium, 4-ethyl-4-methyl-morpholium, 4-methyl-4-propylmorpholinium, 4-butyl-4-methyl-morpholinium, 4-hexyl-4-methyl-morpholinium, 4- Methyl 4-octyl-morpholinium, 4,4-diethyl-morpholinium, 4-ethyl-4-propyl-morpholinium, 4-ethyl-4-butyl-morpholinium, 4-ethyl-4-hexyl-morpholinium, 4-ethyl 4-octylmorpholinium, 4,4-dipropylmorpholinium, 4,4-dibutylmorpholinium, 4,4-dihexylmorpholinium and 4,4-dioctylmorpholinium.

Particularly preferred cations of group (VII) are

The open-chain guanidinium cations: guanidinium, 1,1,3,3-tetramethyl-guanidinium, 1,1,3,3,4-pentamethyl-guanidinium, 4-ethyl-1,1,3,3-tetramethyl-guanidinium , 1,1,3,3-Tetramethyl-4-propyl-guanidinium, 4-isopropyl-1,1,3,3-tetramethyl-guanidinium, 4-butyl-1,1,3,3-tetramethyl-guanidinium, 1 , 1,3,3,4,4-hexamethyl-guanidinium, 4-ethyl-1,1,3,3,4-pentamethyl-guanidinium, 1,1,3,3,4-pentamethyl-4-propyl- guanidinium, 4-isopropyl-1, 1, 3,3,4-pentamethyl-guanidinium, 4-butyl-1,1,3,3,4-pentamethyl-guanidinium, 1,1,3,3-tetraethyl-4, 4-dimethyl-guanidinium, 1,1,3,3-tetrabutyl-4,4-dimethyl-guanidinium, 1,1,3,3-tetrahexyl-4,4-dimethyl-guanidinium, 4,4-dimethyl-1, 1, 3,3-tetraoctyl-guanidinium and 1, 3-diethyM, 3-dibutyl-4,4-dimethyl-guanidinium;

The cyclic guanidinium cations:

1, 3-ethylene-1, 3,4-trimethyl-guanidinium, 4-ethyl-1,3-ethylene-1,3-dimethyl-guanidinium, 1,3-ethylene-1,3-dimethyl-4-propyl- guanidinium, 4-butyl-1,3-ethylene-1,3-dimethyl-guanidinium, 1,3-ethylene-1,3,4,4-tetramethyl-guanidinium, 4-ethyl-1,3-ethylene-1, 3,4-trimethyl-guanidinium, 1, 3-ethylene-1, 3,4-trimethyl-4-propyl-guanidinium and 4-butyl-1,3-ethylene-1,3,4-trimethyl-guanidinium, and

1, 3,4-trimethyl, 3-propylene-guanidinium, 4-ethyl-1,3-dimethyl-1,3-propylene-guanidinium, 1,3-dimethyl-4-propyl-1,3-propylene-guanidinium, 4-butyl-1,3-dimethyl-1,3-propylene-guanidinium, 1,3,4,4-tetramethyl, 3-propylene-guanidinium, 4-ethyl-1,3,4-trimethyl, 3-propylene guanidinium, 1, 3,4-trimethyl-4-propyl-1,3-propylene-guanidinium and 4-butyl-1,3,4-trimethyl-1,3-propylene-guanidinium.

Particularly preferred cations of group (VII) are:

1-Butyl-3-methyl-benzotriazolium, 1-butyl-3-ethyl-benzotriazolium, 1-butyl-3-propyl-benzotriazolium, 1, 3-dibutyl-benzotriazolium and 1-benzyl-3-methyl-benzotriazolium.

Particularly preferred cations of the group (IX) are

1-methyl quinolinium, 1-ethyl quinolinium, 1-propyl quinolinium, 1-butyl quinolinium, 1-hexyl quinolinium, 1-octyl quinolinium, 1-decyl quinolinium, 1-dodecyl quinolinium, 1- Tetradecyl quinolinium, 1-hexadecyl quinolinium and 1-octadecyl quinolinium.

Particularly preferred cations of the group (X) are:

1-methylisoquinolinium, 1-ethylisoquinolinium, 1-propylisoquinolinium, 1-butylisoquinolinium, 1-hexylisoquinolinium, 1-octylisoquinolinium, 1-decyl isoquinolinium, 1-dodecyl-isoquinolinium, 1-tetradecyl-isoquinolinium, 1-hexadecyl-isoquinolinium and i-octadecyl-isoquinolinium.

Particularly preferred cations of the group (XI) are: 1,2-dimethylpyrazolium, 1,2,4-trimethylpyrozolium, 1,2-diethylpyrazolium and 1,2,4-triethylpyrazolium.

Particularly preferred cations of the group (XII) are:

1-Methyl-1,4-diazabicyclo [2.2.2] octan-1-ethyl, 1-ethyl-1,4-diazabicyclo [2.2.2] octan-1-ium, 1-propyl-1, 4- diazabicyclo [2.2.2] octan-1-ium, 1-butyl-1, 4-diazabicyclo [2.2.2] octane-1-ium, 1-pentyl-1,4-diazabicyclo [2.2.2] octane 1-ium, 1-hexyl-1,4-diazabicyclo [2.2.2] octane-1-yl, 1-heptyl-1,4-diazabicyclo [2.2.2] octane-1-yl, 1-octyl 1,4-diazabicyclo [2.2.2] octan-1-yl, 1-nyl-1, 4-diazabicyclo [2.2.2] octane-1-ium and 1-decyl-1,4-diazabicyclo [2.2 .2] octane-1-ium.

As anions, all anions are suitable in principle, which can lead to an ionic liquid in the context of the present invention in conjunction with cations according to the invention.

For example, without limitation of generality, suitable anions [Z ™ ^~ ] are

I

(A) the halides

Fluoride (F ^" ), chloride (Cl ^" ), bromide (Br ^" ) and iodide (P);

(B) the polyhalides

Tribromide (Br ₃ ^~ ), triiodide (I ₃ ^" ), iododibromide (IBr ₂ ^" ), diiodobromide (I ₂ Br ^" ), pentaiodide (I ₅ ^" ) and heptaiodide (I ₇ ^" );

(C) the pseudohalides

Cyanide (CN ^" ), cyanate (OCN ^" ), thiocyanate (SCN ^" ), selenocyanate (SeCN ^" ) and dicyanamide [N (CN) ₂ ^" ]; (D) the phosphates of the general formulas H ₂ PO ₄ ^" , HPO ₄ ^2" , PO ₄ ^{3 "} , (R ^A O) (R ^B O) PO ₄ ^" , H (R ^A O) PO ₃ ^" and (R ^A O) PO ₃ ^{2 ~} and hexafluorophosphate (PF ₆ ^" ), tris (pentafluoroethyl) trifluorophosphate [(C ₂ Fs) ₃ PF ₃ I tris (heptafluoropropyl) trifluorophosphate [(C ₃ F ₇ ) ₃ PF ₃ ^~ ] and tris (nonafluorobutyl) -trifluorophosphat

(E) the phosphites of the general formula (R ^A O) (R ^B O) PO ^" ;

(F) the phosphonates of the general formulas R ^A HPO ₃ ^" , R ^A PO ₃ ^{2 ~} and R ^A (R ^B O) PO ₂ ^" ;

(G) the phosphinates of the general formula R ^A R ^B PO ₂ ^" ;

(H) the sulfates of the general formulas HSO ₄ ^" , SO ₄ ^2" and (R ^A O) SO ₃ ^" ;

(I) the sulfonates of the general formula R ^A SO ₃ ^~ ;

(J) the borates of the general formulas BO ₃ ^{3 "} , HBO ₃ ^2" , H ₂ BO ^{3 "} , (R ^A O) (R ^B O) BO ^" , (R ^A O) HBO ₂ ^" , (R ^A O ) BO ₂ ^{2 "} (R ^A O) (R ^B O) (R ^C O) (R ^D O) B ^" as well as tetrafluoroborate (BF ₄ ^" ),

Tetrachloroborate (BCI ₄ ^" ), tetracyano borate ([B (CN) ₄ ], bis (oxalato) borate [B (O ₂ C-CO ₂ J ₂ ], bis (malonato) borate [B (O ₂ C-CH ₂ - CO ₂ J ₂ ^" ], bis (benzene-1,2-diolato) borate [B (OC ₆ H ₄ O) ₂ ], bis (2,2'-biphenyl-1, r-diolato) borate [B (OC ₆ H ₄ -C ₆ H ₄ O) ₂ I and bis (salicylato) borate [B (OC ₆ H ₄ -CO ₂ ) ₂ ^" 1;

(K) the boronates of the general formula R ^A HBO ₂ ^" , R ^A BO ₂ ^2" and R ^A (R ^B O) BO ^~ ; (L) the carboxylates of the general formula R ^A CO ₂ ^~ ;

(M) the carbonates of the general formula HCO ₃ ^" , CO ₃ ^2" and (R ^A O) CO ₂ ^" ;

(N) the alkoxides of the general formula RO ^" ;

(O) and the anions

Bis (trifluoromethylsulfonyl) imide (NTf ₂ ^" ), bis (pentafluoroethylsulfonyl) imide [(C ₂ F ₅ SO ₂ J ₂ NI, tricyanomethide [C (CN) ₃ ^" ], tris (trifluoromethylsulfonyl) methide (CTf ₃ ^" ), hexafluoroantimonate (SbF ₆ ^" ), hexafluoroarsenate (AsF ₆ ^" ), nitrate (NO ₃ ^" ), nitrite (NO ₂ ^" ), tetrachloroferrate (III) (FeCl ₄ ^" ), tetrabromoferrate (III) (FeBr ₄ ^" ), tetrachloroaluminate (AICI ₄ ^" ), heptachlorodialuminate (Al ₂ Cl ₇ ^" ),

Decachlorotrialuminate (Al ₃ Clκf), tetrabromoaluminate (AIBr ₄ ^" ), hexafluorosilicate (SiF ₆ ^2" ) and hexacyanoferrate (III) ([Fe (CN) ₆ ] ^{3 "} ).

In the abovementioned general formulas (D) to (N), the radicals R ^A to R ^D independently of one another represent a monovalent, carbon-containing and carbon-bonded, saturated or unsaturated, linear or branched, acyclic or cyclic, aliphatic, aromatic radical or araliphatic, unsubstituted, partially or completely halogenated or interrupted by 1 to 5 heteroatoms or functional groups radical or having 1 to 30 carbon atoms;

• two adjacent radicals from the series R ^A to R ^D together also for a divalent, carbon-containing and carbon-bonded, saturated or unsaturated, linear or branched, acyclic or cyclic, aliphatic, aromatic or araliphatic, unsubstituted, partially or completely halogenated or by 1 to 5 heteroatoms or functional groups interrupted or substituted radical having 1 to 30 carbon atoms. AIs particularly preferred heteroatoms, which may occur in the radicals R ^A to R ^D, may be mentioned oxygen, sulfur, selenium, tellurium, nitrogen, phosphorus and silicon.

Very particularly preferred anions of the ionic liquids in the context of the present invention are tetrafluoroborate (BF ₄ ^" ), hexafluorophosphate (PF ₆ ^" ),

Hexafluoroantimonate (SbF ₆ ^" ), hexafluoroarsenate (AsF ₆ ^" ), methanesulfonate (OMs ^" ),

Trifluoromethanesulfonate (OTf ^" ), 4-toluenesulfonate (OTs ^" ), acetate (CH ₃ CO ₂ ^" ),

Trifluoroacetate (CF ₃ CO ₂ ^" ), bis (trifluoromethylsulfonyl) imide (NTf ₂ ^" ), nitrate (NO ₃ ^" ),

Dihydrogen phosphate (H ₂ PO ₄ ^" ), dimethyl phosphate [(MeO) ₂ PO ₂ ^" ], diethyl phosphate [(EtO) ₂ PO ₂ -], hydrogen sulfate (HSO ₄ ^" ), methylsulfate (MeOSO ₃ ^" ), ethyl sulfate (EtOSO ₃ ^"

), Thiocyanate (SCN ^" ), dicyanamide [N (CN) ₂ ^" ], tricyanomethide [C (CN) ₃ I glycolate

[HOCH ₂ CO ₂ η, lactate [CH ₃ CH (OH) CO ₂ I.

Suitable metal salts in the context of the present invention are salts formed from cations and anions, in which the cation and / or the anion contains one or more metal atoms. In this case, the metal atoms in the cation can be free, that is, simple metal cations of any value, or by any desired

Number of neutral and / or anionic, organic or inorganic ligands of any denticity complexed. The metal atoms in the anion must be complexed by any number of neutral and / or anionic, organic or inorganic ligands of any denticity.

embodiments

Example 1 :

AgBF ₄ (0.035 g, 0.179 mmol) and (0.040 g, 0.319 mmol) of 1-butyl-imidazole are dissolved in 1-butyl-3-methyl-imidazolium-tetrafluoroborate (2 g) under argon and light-exclusion at room temperature. The resulting solution contains about 1% silver. The solution is transferred under argon into a stainless steel autoclave and dried for 20 minutes in a high vacuum at about 0.1 mbar. The autoclave is then filled directly with hydrogen up to a pressure of 4 bar and the reaction mixture is heated to 85 ° C. for 2 hours. Finally, the stainless steel autoclave is evacuated again and kept for 1 hour at 100 ⁰ C under high vacuum at about 0.1 mbar to excess 1-butyl-imidazole from the Remove reaction mixture. The characterization of the silver nanoparticles formed is done in situ by TEM and shows that the reaction is complete. The mean particle size is 2.80 ± 0.78 nm with a minimum size of 1.25 nm and a maximum size of 4.68 nm.

Example 2:

AgPF ₆ (0.010 g, 0.040 mmol) and (0.012 g, 0.096 mmol) 1-butyl-imidazole are dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate (2 g) under argon and light at room temperature. The resulting solution contains about 0.15% silver. The solution is transferred under argon into a stainless steel autoclave and dried for 20 minutes in a high vacuum at about 0.1 mbar. The autoclave is then filled directly with hydrogen up to a pressure of 4 bar and the reaction mixture is heated to 85 ° C. for 2 hours. Finally, the stainless steel autoclave is evacuated again and kept for 1 hour at 100 ⁰ C in a high vacuum at about 0.1 mbar to remove excess 1-butyl-imidazole from the reaction mixture. The characterization of the silver nanoparticles formed is done in situ by TEM and shows that the reaction is complete. The mean particle size is 4.36 ± 1, 25 nm with a minimum size of 2.04 nm and a maximum size of 9.75 nm. Π

Claims

claims

1. A process for the preparation and stabilization of functional metal nanoparticles in the particle size range of 0.1 to 1000 nm by reduction of soluble metal salts with hydrogen in ionic liquids, characterized in that a narrow particle size distribution is achieved by adding a proton scavenger to the reaction mixture.

2. A process according to claim 1, characterized in that a nitrogen base is added as a proton scavenger to the reaction mixture, which in its protonated form has a molar volume similar to that of the cation of the ionic liquid used.

3. A process according to claims 1 and 2, characterized in that the nitrogen base used as proton scavenger is the nitrogen base underlying the cation of the ionic liquid used.

4. A method according to any one of claims 1 to 3, characterized in that the anion of the metal salt similar or identical to the

Anion of the ionic liquid used is.

5. A process according to any one of claims 1 to 4, characterized in that the ionic liquid used is a salt of cations [Q ^{n +} ] and anions [Z ^m T built salt of the general formula [Q ^{n +} ] _m [Z ¹ ^ _n or a Mixture of several such salts, where n = m or n ≠ m and 1 ≤ n ≤ 4 and 1 <m <4 and those ionic liquids are particularly preferred in which n = m = 1.

6. A method according to any one of claims 1 to 5, characterized in that the ionic liquid used has a melting point <180 ° C, preferably <120 ° C and most preferably <100 ° C.

7. A method according to any one of claims 1 to 6, characterized in that the cation of the ionic liquid used, an imidazolium, ammonium, pyrrolidinium, piperidinium, pyridinium, morpholinium, guanidinium, benzotriazolium, quinolinium , Isoquinolinium, pyrazolium, 1,4-diazabicyclo [2.2.2] octan-1-ium, 1, 2,4-triazolium,

Pyridazinium, pyrimidinium, pyrazinium, 1, 3,5-triazinium, 1, 2,3-triazolium, piperazinium, oxazolium, oxazolidinium, thiazolium, quinoxalinium, benzimidazolium, imidazolidinium, indolinium or thiomorpholinium cation.

8. A method according to any one of claims 1 to 7, characterized in that the anion of the ionic liquid used, a halide, polyhalide, pseudohalide, phosphate, phosphite, phosphonate, phosphinate, sulfate, sulfonate, borate, boronate, carboxylate, carbonate, Alkoxide or bis (trifluoromethylsulfonyl) imide (NTf ₂ ^" ), bis (pentafluoroethylsulfonyl) imide

Tricyanomethide [C (CN) ₃ ^" ], tris (trifluoromethylsulfonyl) methide (CTf ₃ ^" ), hexafluoroantimonate (SbF ₆ ^" ), hexafluoroarsenate (AsF ₆ ^" ), nitrate (NO ₃ ^" ), nitrite (NO ₂ ^" ), tetrachloroferrate (III) (FeCl ₄ ^"), tetrabromoferrate (III) bromide (FeBr _^4"), tetrachloroaluminate (AlCl ₄ -), Heptachlorodialuminiat (AI ₂ CI ₇ ^"), Decachlorotrialuminat (AI ₃ Clio ^~) Tetrabromoaluminat (AlBr _^4"), hexafluorosilicate

(SiF ₆ ^{2 "} ) or hexacyanoferrate (III) ([Fe (CN) ₆ ] ^3" ).

9. A method according to any one of claims 1 to 8, characterized in that it is the ionic liquid used is a hydrophobic, immiscible with water ionic liquid.

10. A process according to any one of claims 1 to 9, characterized in that the metal nanoparticles produced are isolated from the initially obtained metal nanoparticle dispersion.

11. A process according to any one of claims 1 to 10, characterized in that the initially obtained metal nanoparticle dispersion is treated with air, oxygen or another suitable oxidizing agent and thereby metal oxide nanoparticles are obtained.

12. A method according to any one of claims 1 to 11, characterized in that it is the manufactured nanoparticles to Silberig), copper (Cu), cobalt (Co), iron (Fe), Iridiυm- (lr) , Rhodium (Rh), palladium (Pd), platinum (Pt), gold (Au), ruthenium (Ru), (nickel (Ni), zinc (Zn),

Cadmium (Cd), manganese (Mn), rhenium (Re), chromium (Cr), molybdenum (Mo), tungsten (W), vanadium (V), niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), hafnium (Hf), scandium (Sc) or yttrium nanoparticles (Y).

13. A method according to any one of claims 1 to 11, characterized in that after the isolation of the metal nanoparticles, the ionic liquid used is recovered, purified and reused for further reactions.

14. Use of the metal nanoparticle dispersion obtained according to at least one of claims 1 to 9 directly as an active material in catalytic processes.

15. Use of the metal nanoparticle dispersion obtained according to at least one of claims 1 to 9 directly as an active sensor component.

16. Use of the metal nanoparticle dispersion obtained according to at least one of claims 1 to 9 directly or after a downstream formulation step as an antimicrobial coating or as a decontamination paint.