Molybdenum disulfide nanoparticles: synthesis process and uses

Abstract

The present invention relates to a process for preparing molybdenum disulfide nanoparticles by sulfidation of a molybdenum organometallic complex in the presence of a ligand. The process consists of reacting a solution of a Mo(η6-arene)2 complex with a solution containing a sulfur compound and a ligand. The resulting nanoparticles consist of a molybdenum disulfide core with which the ligand forms a covalent bond. The nanoparticles can be used for catalyzing organic syntheses, including transamidation. Fig. 1.

Description

Title of the invention: Molybdenum disulfide nanoparticles, synthesis process and uses technical field

[0001] The present disclosure relates to molybdenum disulfide nanoparticles and a process for their preparation.

[0002] It also relates to their use in application areas such as catalysis, in particular nanocatalysis of synthesis reactions of organic molecules. Previous technique

[0003] Molybdenum disulfide is a transition metal dichalcogenide with the chemical formula MoS2. This solid, which naturally has a lamellar structure, comprises one or more layers, each layer itself being composed of a plane of metal cations flanked by two planes of sulfides. The Mo-S bonds are covalent within the layers, which are held together by Van der Waals forces.

[0004] Several synthetic routes for molybdenum disulfide nanoparticles have been explored, resulting in a variety of morphologies associated with specific physicochemical properties. Consequently, molybdenum disulfide is used in numerous application areas, including catalysis. These nanoparticles exhibit catalytic activity in photoinduced dihydrogen production, hydroconversion of petroleum residues and hydrosulfurization processes, lithium-ion batteries, and supercapacitors.

[0005] This is the case for "nanosheets" obtained by exfoliation of bulk molybdenum disulfide. Their length is on the order of 75 nm to 100 nm and their thickness ranges from 0.65 nm to approximately 10 nm (corresponding to a number of sheets ranging from approximately 1 to 10).

[0006] Molybdenum disulfide has also been synthesized in the form of quantum dots, obtained by reducing the length of the nanosheets to values ​​ranging from approximately 1.5 nm to 5 nm.

[0007] The need therefore remains to propose molybdenum disulfide-based nanoparticles with improved properties.

[0008] Furthermore, prior art processes for synthesizing nanoparticles are complex, and it would be desirable to be able to obtain them by a simplified process, in particular by reducing the number of steps. It would also be desirable to be able to carry out this synthesis using a reduced number of reagents and, preferably, without using additives in the reaction mixture, such as polymers.

[0009] Finally, paracetamol, a widely used active ingredient in medicine, is obtained by the acylation of aminophenol with acetic anhydride. However, this process has many drawbacks. First, acetic anhydride is a highly corrosive product, sensitive to air and humidity, which requires working in an anhydrous environment and the use of more expensive, specialized equipment. It is also listed as a precursor in Schedule II of the DEA in the United States, and its use is restricted in many other countries. Second, since the reaction is rapid but not entirely selective, byproducts such as (4-hydroxyphenyl)propanamide (also called N-(4-hydroxyphenyl)propanamide or "Acetaminophen related compound B" or "Paracetamol Impurity B") and 4-acetoxyacetanilide are formed alongside acetic acid, which is generated in stoichiometric quantities by the acylation.These by-products must be eliminated in several stages, which complicates the purification of paracetamol.

[0010] The need therefore remains to propose a process for the synthesis of organic molecules such as paracetamol, which is free, at least in part, from the disadvantages inherent in the aforementioned known configuration, and in particular, which includes fewer reaction steps, which is less expensive to implement, and which does not use toxic reagents.

[0011] It would also be advantageous to propose a process for synthesizing organic molecules that could lead to better yields thanks to a nanocatalyst, which would not only be more active but also recyclable.

[0012] The Applicant acts, at all stages of aircraft design and development, on parameters that enable the production of more environmentally friendly components and products, the integration and use of which in civil aviation have minimized environmental consequences. Consequently, the Applicant continuously works to reduce its negative climate impact by employing methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions and consume less energy, in order to reduce the environmental footprint of its activity. Description of the invention

[0013] The present presentation addresses at least one of the problems that have just been presented by proposing a new molybdenum disulfide-based nanomaterial that is recyclable, very small in size and has particular surface properties resulting from the presence of a ligand, which can be an organic molecule.

[0014] This material makes it possible in particular to offer an alternative to the classic synthesis route of paracetamol by acylation, by taking advantage of its catalytic properties.

[0015] It also has the advantage of increasing the yield of chemical reactions catalyzed with bulk molybdenum disulfide, which are known from the prior art. Finally, it is suitable for being mixed directly with the reagents of an organic synthesis, or with the compounds used in the preparation of a liquid lubricant composition, without any special precautions.

[0016] The present description also outlines a process for synthesizing this molybdenum disulfide-based nanomaterial. The organometallic approach, involving the sulfidation of a molybdenum complex with an arene in the presence of one or more ligands, differs from prior art processes in that it allows the production of nanoparticles with a highly specific structure, resulting in improved catalytic properties. This process offers several advantages, including a reduced environmental footprint and the potential for industrial-scale application. Indeed, it can be carried out at room temperature and atmospheric pressure in a single step, without the use of additives, and using bio-based reagents that are abundant in nature. The reaction time can be very rapid. Finally, the uniformity of shape and size of the nanoparticles is easily reproducible.

[0017] The new nanomaterial can be advantageously used for various chemical reactions, including transamidation.

[0018] The invention therefore proposes a transamidation synthesis process for organic molecules such as paracetamol, catalyzed by this nanomaterial. This process advantageously offers an alternative to organic syntheses catalyzed by molybdenum disulfide, which have low yields, require numerous purification steps, and necessitate specialized equipment to create the reaction conditions. The nanoparticles differ from prior art catalytic transamidation syntheses by exhibiting a significantly higher reactivity than bulk molybdenum disulfide or molybdenum disulfide nanoparticles with a structure different from that described herein. In particular, they allow for a reduction in reaction time, the use of milder conditions, and a reduction in the amount of catalyst required.The invention is therefore distinguished from other catalytic approaches by a very low catalyst content and an increased reaction rate.

[0019] The aforementioned features and advantages, as well as others, will become apparent from the detailed description that follows and from the examples of implementation. This detailed description refers to the accompanying figures. Brief description of the figures

[0020] Figure 1 shows a spectrum obtained by X-ray photoelectron spectroscopy (XPS) of disulfide nanoparticles. of molybdenum according to the invention and two other molybdenum compounds used as reference.

[0021] Figure 2 reproduces an image obtained by atomic force microscopy (ARM or "Atomic Resolution Microscopy" in English) of the molybdenum disulfide nanoparticles according to the invention.

[0022] Figure 3 shows the 1H NMR spectra of the reaction medium before the start of the reaction (top spectrum) and at the end of the reaction (bottom spectrum) of a synthesis process according to the invention by transamidation of dimethylformamide with benzylamine to form benzylamide.

[0023] Fig. 4 reproduces the mass spectrum of paracetamol obtained by a synthesis process of the invention catalyzed by molybdenum disulfide nanoparticles observed in Fig. 2. Description of the implementation methods

[0024] Thus, the first object presented in this exposition relates to a process for preparing molybdenum disulfide in the form of nanoparticles, said process comprising the reaction between: - a solution of an organometallic molybdenum complex of formula Mo(q6-arene)2 in a first organic solvent, and - a solution of a sulfur donor and at least one ligand, in a second organic solvent.

[0025] This process involves the sulfidation of a molybdenum organometallic complex in the presence of a ligand.

[0026] The term “nanoparticles” refers to objects whose dimension is preferably less than 20 nm.

[0027] In the present description, a "ligand" is a monomeric organic molecule composed of at least one polar functional group and at least one linear, unsaturated or saturated, branched or cyclic carbon chain. The ligand is capable of forming a strong or weak bond with molybdenum disulfide, for example, a coordination bond with molybdenum and / or sulfur atoms.

[0028] The term "arene" in this description refers to benzene or a benzene derivative comprising a benzene ring and at least one substituent group, each of which may comprise one or more heteroatoms. The arene may be benzene or a benzene molecule substituted with at least one aliphatic alkyl group, saturated or unsaturated, linear or branched, having from 1 to 6 carbon atoms.

[0029] For example, the arene is chosen from benzene, toluene, mesitylene (1,3,5-trimethylbenzene), ethylbenzene, isoproprylbenzene, tert- butylbenzene, methylnaphthalene, methylbenzoate, benzene chloride and dimethylaminebenzene.

[0030] In a particular embodiment, the arene is a benzene molecule substituted by one, two or three saturated aliphatic alkyl groups having from 1 to 3 carbon atoms.

[0031] The organometallic complex of molybdenum is commercially available or can be synthesized by methods known to those skilled in the art, such as, for example, the methods described in the articles J. Am. Chem. Soc. 1974, 96, 6, 1945-1946 and Dalton Trans., 2006, 4228-4234.

[0032] Its structure comprises a molybdenum atom flanked by two arene ligands, which may be of the same or different natures, whose benzene rings are parallel. The six atoms of each benzene ring are present within the coordination sphere of molybdenum (q6), such that the molybdenum cannot be bonded to any other ligand, in particular to any oxygen atom of another ligand. The electrical charge of the complex in the first solution is neutral.

[0033] The sulfur donor can be a simple element of sulfur (also referred to as "sulfur" in this description) and can be chosen from the solid allotropic forms of sulfur, the polymorphs of its allotropes, and mixtures thereof. It can be of natural or synthetic origin, amorphous or crystalline.

[0034] The sulfur donor can also be a molecule containing one or more sulfur atoms and potentially one or more heteroatoms, such as H2S, [R3Si]2S, RSH, R3PS, or (NR2)2CS where R represents an alkyl or aryl.

[0035] Among the allotropes of solid sulfur are compounds of formula Sn for which n is an integer greater than or equal to 6, in particular cyclo-S n compounds. The sulfur can thus be chosen from cyclooctasulfur (of formula cyclo-S8), cyclohexasulfur (cyclo-S6) and cycloheptasulfur (cyclo-S7). Other cyclic allotropes can be used such as, for example, cyclo-S[2.

[0036] In a particularly advantageous embodiment, the sulfur used for the synthesis of the nanoparticles comes from an ore and essentially comprises cyclo-S8 in alpha or gamma crystalline form. Indeed, the abundance of this raw material makes it an inexpensive reagent. Cyclo-S8 in beta crystalline form, obtained from the alpha form, can also be used.

[0037] The purity of the sulfur is preferably greater than 99%.

[0038] The ligand may be an organic molecule comprising at least one polar group Y and at least one hydrocarbon chain R. The hydrocarbon chain may It may include a heteroatom, be saturated or unsaturated, linear or branched. R can be aliphatic or aromatic.

[0039] The number of polar group(s) is preferably equal to 1 or 2. Thus, the ligand can be represented by the formula RY or YRY when it comprises respectively one or two polar groups located at the end or at both ends of the hydrocarbon chain R.

[0040] In a particular embodiment, the polar group Y comprises at least one heteroatom whose oxygen, and it is located at one end of the hydrocarbon chain.

[0041] The polar group preferably comprises a hydroxyl (-OH). It is preferably a carboxyl (-COOH).

[0042] It is particularly advantageous to choose a bio-based, natural, or naturally derived organic ligand, for example, a bio-based organic ligand chosen from saturated or unsaturated, aliphatic or aromatic fatty acids, which are derived from vegetable oils based on naturally occurring fatty acid triglycerides. Examples of vegetable oils are olive, corn, cottonseed, linseed, soybean, and sunflower seed oils.

[0043] For example, an unsaturated aliphatic monocarboxylic fatty acid comprising at least one carbon-carbon double bond, which is linear, is chosen, such as an unsaturated aliphatic fatty acid having 12 to 20 carbon atoms. The unsaturated aliphatic fatty acid may be chosen from lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid and gadoleic acid.

[0044] A C12-C20 saturated fatty acid chosen from lauric, myristic, palmitic, stearic and arachidic acids can also be chosen as a ligand.

[0045] The molecular mass of the ligand is preferably between 180 g / mol and 320 g / mol, more preferably between 200 g / mol and 300 g / mol.

[0046] In a particular embodiment the ligand is oleic acid (also called octadecenoic acid).

[0047] The process may employ one or more ligands as described above. For example, the process uses a mixture of several fatty acids. In a particular embodiment, the fatty acid mixture comprises oleic acid combined, for example, with palmitic acid.

[0048] The ligand is preferably used in an amount greater than the equimolar amount of molybdenum atoms. Furthermore, the nature and amount of the first organic solvent are chosen so as to dissolve the molybdenum organometallic complex. Similarly, the nature and amount of the second organic solvent are chosen to dissolve both the sulfur compound and the ligand.

[0049] Also, the concentrations of reactants in each solution and the volume ratio between the two solutions are advantageously chosen so that the species remain in solution in the mixture of the two solutions and the molar ratio between the ligand and the organometallic complex of molybdenum is greater than 0.5.

[0050] In a particular embodiment, the molar ratio between the ligand and the organometallic complex of molybdenum is between 0.5 and 15. It preferably goes from 5 to 7, and can be equal to 5. A person skilled in the art will know how to choose the value of the molar ratio so that the colloidal solution of the nanoparticles is stable.

[0051] An “organic solvent” is a liquid compound at the reaction temperature between the molybdenum organometallic complex, the sulfur donor, and the ligand. It is preferably chosen from common organic solvents and their derivatives.

[0052] The first organic solvent and / or the second solvent can each and independently of each other be made up of a mixture of solvents comprising an organic solvent (from which any traces of water it contains can be removed and which can be degassed), and another solvent, organic or inorganic, miscible or immiscible with said organic solvent.

[0053] The first solvent and the second solvent are preferably chosen independently of each other from aromatic hydrocarbons such as benzene and toluene, polar solvents such as tetrahydrofuran, and mixtures thereof.

[0054] The second solvent is advantageously identical to the first solvent, and preferably identical to the arena of the complex, which makes it possible to limit the number of reagents required to carry out the process.

[0055] The solution of the organometallic complex Mo(q6-arene)2 is preferably added all at once and under stirring to the solution comprising the sulfur donor and the ligand.

[0056] The reaction step can be carried out at a temperature between -50 °C and 100 °C.

[0057] In a highly advantageous embodiment of the process of the invention, the reaction step is carried out at a temperature between 20°C and 30°C and at atmospheric pressure, which considerably reduces the energy cost of the synthesis process. The reaction time can be very short, for example, less than 10 minutes.

[0058] The solution of the organometallic complex of molybdenum and the solution of the simple body of sulfur and the ligand can also be prepared at a temperature between 20 °C and 30 °C.

[0059] In some embodiments, the reaction step leads to a colloidal dispersion of molybdenum disulfide nanoparticles in the mixture of the first solvent and the second solvent, which dispersion is stable over time.

[0060] The process may include a step of drying the dispersion obtained in order to remove the two solvents and to recover the nanoparticles, which may be in the form of a solid powder, or a liquid.

[0061] The process just described makes it possible to synthesize a new form of molybdenum disulfide nanoparticles, which constitutes a second object of the presentation.

[0062] Thus, the second object of this presentation concerns a molybdenum disulfide compound in the form of nanoparticles comprising a ligand. The ligand conforms to the description given for the first object and will not be repeated in this part.

[0063] More specifically, the compound is in the form of nanoparticles comprising an inorganic molybdenum disulfide core coated on the surface by at least one ligand, the core having an average hydrodynamic diameter of between 1 and 10 nm, for example between 1 nm and 5 nm.

[0064] Nanoparticles are characterized by a very small size, a particular shape, and a character that can be both organic and inorganic, which gives access to new or improved physico-chemical properties.

[0065] Moreover, the nanoparticles form a colloidal dispersion in many solvents, which facilitates their formulation in products intended for specific applications. For example, they are in colloidal dispersion in aromatic solvents, alkanes, and mixtures of these solvents with polar gel solvents such as toluene or tetrahydrofuran.

[0066] The molybdenum disulfide nanoparticles presented in this description have a particular shape. They cannot be considered quantum dots because they do not exhibit quantum confinement. Nor can they be considered sheets because the difference between their two dimensions is very small, for example, 2 nm in height for a width of less than 10 nm. Therefore, the shape of the nanoparticles can be described as that of blocks, sheets, fragments, or pieces of lamellae, or even fragmented sheets.

[0067] The molybdenum disulfide nanoparticles of the invention are preferably surface-coordinated with at least one ligand enabling their stabilization in colloidal form in a solvent. They can be very advantageously obtained from a highly reactive organometallic precursor by means of a synthesis carried out at room temperature, at atmospheric pressure, with a short reaction time (for example, less than 10 minutes), and whose mechanism is similar to a bottom-up mechanism.

[0068] They have a different shape from the nanosheets of the prior art usually described, which are defined by a larger dimension (the length of the sheets) greater than 100 nm, and a thickness (proportional to the number of sheets) of the order of 2 nm. The nanoparticles of the invention have a form factor lower than that of the sheets of the prior art, preferably less than a value chosen from 40, 30, 20 or 15. For example, their length is less than 15 nm when their height is less than 3 nm.

[0069] The average hydrodynamic diameter of the nanoparticles, measured when they are placed in colloidal dispersion in a solvent, can range from 1 nm to 10 nm. The hydrodynamic diameter can be measured by any method known to those skilled in the art, such as microscopy or spectroscopy. For example, the nanoparticles have a hydrodynamic diameter in toluene of between 3 nm and 5 nm when observed by Y-DOS NMR spectroscopy. The process described above makes it highly advantageous to produce nanoparticles that are homogeneous in shape and very small in size, at lower temperatures than those of the processes used in the prior art.

[0070] Furthermore, their structure is characterized by the presence of organic molecules, which coat the surface of a solid molybdenum disulfide core. Each organic molecule is bonded to a molybdenum atom of the molybdenum disulfide core by a covalent and / or coordination bond. The structure of the molybdenum disulfide nanoparticles can be observed using two methods: X-ray photoelectron spectroscopy (XPS) detects the presence of Mo-O bonds, while DOSY / Noesy NMR shows the binding of the ligand to nanometric objects.

[0071] The molybdenum disulfide of the nanoparticles can have a 2H, 1T and / or 3R crystalline structure. Its coherence length can be very short, typically around 1 nm (WAXS). The molybdenum disulfide of the nanoparticles can alternatively be amorphous.

[0072] The size and structure of these nanoparticles gives them physicochemical properties that allow them to be used in many fields of application, such as organic synthesis by nanocatalysis.

[0073] Thus, the present exposition describes a third object relating to a process for the synthesis of an organic compound comprising a reaction step catalyzed by the molybdenum disulfide nanoparticles described previously, by molybdenum disulfide nanoparticles which could be obtained by the process described in the second object above, or which would be directly obtained by this process.

[0074] In one embodiment, the reaction step involved in the catalysis is a transamidation step by reaction of at least one amide and at least one amine. During this step, the transamidation occurs in the presence of the nanoparticles. molybdenum disulfide nanoparticles act as catalysts. This synthetic route shows promise for the conversion of primary or secondary amines, making it suitable for use with numerous target molecules. The catalytic system based on molybdenum disulfide nanoparticles can be used for the synthesis of drugs such as paracetamol, as well as for more complex amides like lidocaine or piperine.

[0075] The amide can be a primary, secondary or tertiary amide, while the amine can be a primary or secondary amine.

[0076] The reaction step of the transamidation process can be represented schematically by the following equation:

[0077] [Chem.l] o \ + rr-' "k" RR x- "...i..................."- \ + R'" 'n t R i R-

[0078] - wherein RI is selected from H and linear or branched alkyl groups comprising from 1 to 20 carbon atoms; and R2 is selected from a phenyl group optionally substituted by one or two -OH, -OCH3, -CH3, -OCH2-CH3 groups; a group of formula -(CH2)nZ in which n ranges from 1 to 12 and Z represents -H, -CH3, a C3-C6 branched alkyl, or a phenyl group optionally substituted by one or two -OH, -OCH3, -CH3, -OCH2-CH3 groups; or in which RI and R2 together represent a saturated aliphatic heterocycle comprising the nitrogen atom, the heterocycle optionally comprising a second nitrogen atom, and the heterocycle being able to be attached to a benzene ring optionally substituted by at least one -OCH3, -Br or -NO2 group,

[0079] - wherein R' is chosen from H, an alkyl group comprising 1 with 6 carbon atoms, an alkenyl possibly substituted by an aromatic group, an aryl such as benzyl, and a phenyl possibly substituted by a methyl; and

[0080] - wherein R” and R'” independently represent H, CH3 or ch2-ch3.

[0081] By way of example, the amine can be chosen from benzylamine (R1=H and R2=benzyl), aminophenol (R1=H and R2=4-hydroxyphenyl), diisopropylamine (R1=isopropyl and R2=isopropyl), tetrahydroisoquinoline, diethylamine (R1=ethyl and R2=ethyl), dodecylamine (R1=H and R2=(CH2)nCH3) and phenylamine (R1=H and R2=phenyl).

[0082] The amide can be selected from dimethylformamide (R'=R”=R'”=H), formamide (R'=CH3 and R”=R”'=H), acetamide (R'=H and R”=R'”=CH3), and benzylamide (R'=benzyl and R”=R'”=H). The transamidation step can be carried out in a nonpolar aprotic aromatic solvent, such as, for example, benzene, optionally substituted with one, two, or three alkyl groups. Toluene is one example.

[0083] The process described herein provides access to paracetamol via a route that does not produce any organic by-products, thus facilitating the separation and purification of paracetamol. Furthermore, this synthesis avoids the use of acetic anhydride, the use of which is complex due to its sensitivity to water and requires more expensive, specialized equipment. The inventors have found a synthetic process that is not sensitive to humidity, resulting in simpler implementation and lower production costs.

[0084] Thanks to the process of the invention, all of the reagent can be converted and no co-products are formed. The reaction medium contains only paracetamol, the excess acetamide introduced, and the catalytic system. The latter can be removed by filtration, centrifugation, or precipitation in a solvent, such as tetrahydrofuran, methanol, or water. The excess acetamide is easily removed by evaporation or by liquid-liquid extraction using two solvents.

[0085] In addition to their use in catalysis, the molybdenum disulfide nanoparticles described above have properties that can be exploited in other fields of application.

[0086] Although the present invention has been described with reference to specific embodiments, a person skilled in the art will be able to make modifications to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and examples should be considered in an illustrative rather than a restrictive sense.

[0087] Furthermore, all the characteristics described with reference to the process for preparing molybdenum disulfide nanoparticles are transposable, alone or in combination, to the nanoparticles themselves, and vice versa.

[0088] Example 1: Synthesis of MoS2 nanoparticles according to the invention Protocol:

[0089] The synthesis is carried out in a glove box under an atmosphere of argon or dinitrogen.

[0090] 5 g of MoC15 (18 mmol) are mixed with 12 g of A1C13 (90 mmol) and 0.7 g of aluminum powder (26 mmol) for a few minutes. Then, 75 ml of toluene. Dried and degassed toluene is added, and the reaction is left under stirring at 125 °C in a Schlenk flask for 36 hours. Excess toluene is then removed by evaporation under vacuum. After complete drying, a black residue is obtained. A potassium hydroxide solution (400 mL H₂O, 90 g KOH) is degassed and cooled in an ice bath for one hour. The cold solution is slowly added to the black residue in an ice bath using a cannula. An olive-green solution is obtained and stirred at room temperature for 6 hours. The reaction mixture is then filtered and washed twice with 200 mL of degassed water. The dark green to brown residue is then dried under vacuum for at least 10 hours to obtain a dry solid, which is subsequently sublimated under low pressure (200 mTorr) and gentle heating (65 °C) to obtain molybdenum bis-toluene.

[0091] Molybdenum bis-toluene is then dissolved in 0.5 mL of toluene.

[0092] Separately, powdered sulfur (previously dried and degassed under vacuum) Molybdenum disulfide is dissolved with oleic acid (AO) in 0.5 mL of degassed toluene at 100°C. After homogenization, the molybdenum bis-toluene solution is added all at once to the sulfur solution containing oleic acid, while stirring, resulting in an immediate color change from green to black, the characteristic color of MoS2 nanoparticles. The resulting solution, containing molybdenum disulfide nanoparticles surface-grafted with oleic acid, is hereafter referred to as "MoS2(5 AO)". The mass and molar amounts of the reactants and the product obtained are given in Table 1. [Tables 1] Mo(Tol)2 Sulfur S Oleic acid (AO) MoS2(5 AO) Number of moles (mmol) 0.03 0.06 0.15 0.03 Mass (mg) 8.4 2 42 47.2 Nature of nanoparticles:

[0093] The nanoparticles are characterized by XPS (see [Fig. 1]). The spectra include signals from molybdenum disulfide (1253-1257 eV) as well as a signal at 1250 eV characteristic of Mo-O bonds arising from the attachment of oleic acid to the surface of the nanoparticles.

[0094] EDX analyses establish an average sulfur / molybdenum ratio of 1.7+0.2. This stoichiometry corresponds well to that of a MoS2 with a slight understoichiometry in sulfur. Size

[0095] The MoS2(5 AO) nanoparticles from the colloids differ from nanosheets and quantum dots according to the prior art. They are very small, with the smallest particles having a size of less than a nanometer (see the ARM image in [Fig. 2]).

[0096] Measurements by DOS Y NMR spectroscopy make it possible to estimate the hydrodynamic diameter of nanoparticles in colloidal solution at an average size between 3 nm and 4 nm. Stabilization

[0097] The colloids thus obtained are stable over time; UV-visible absorption measurements over time show that there is no evolution of the colloid over several months.

[0098] Example 2: Preparation of benzylamide by transamidation with MoS2 nanoparticles according to the invention and MoS2 according to the prior art

[0099] Two nanocatalytic transamidation syntheses between benzylamine and dimethylformamide (DMF) were carried out using molybdenum disulfide nanoparticles prepared according to Example 1. The solution obtained in this example can be used directly as a catalyst and mixed with the organic reagents without any special precautions. The reaction scheme is reproduced below.

[0100] [Chem.2] Protocol#:

[0101] The MoS2(5 AO) of Example 1 and benzylamine are dissolved in an excess of DMF, used both as a reactant and a reaction solvent. The solution is poured into a closed 20 mL tube and heated to 150 °C under ambient air. Stirring is achieved by refluxing the solvent.

[0102] [Table 2]

[0103] Quantity of reactants in the first synthesis according to the invention (Aa 106) Reagents Volume (ml) Mass (mg) Amount of substance (mmo 1) Benzylamine 0.1 - 0.91 Dimethylformamide 0.5 - 34 MoS2 (5 AO) of Example 1 - 23.6 0.045 (5 mol % relative to the amine) [Table 3]

[0104] Quantity of reactants in the second synthesis according to the invention (Aa 107) Reagents Volume (ml) Mass (mg) Amount of substance (mmol) Benzylamine 0.163 - 1.5 Dimethylformamide 0.5 - 34 MoS2 (5 AO) of Exemp pie 1 - 23.6 0.015 (1 mol % relative to the amine) A third synthesis was carried out by replacing the molybdenum sulfide according to the invention with crude MoS2 colloids prepared according to the same process as described above, except that oleic acid is not added.

[0105] [Table 4]

[0106] Quantity of reactants in the prior art synthesis (Aa 109) Reagent Volume (ml) Mass (mg) Amount of substance (mmol) Benzylamine 0.163 - 1.5 DMF 0.058 - 5 MoS2 - 23.6 0.015 (1 mol % relative to the amine) Characterization of the amide obtained in the first synthesis

[0107] The catalyst is recovered from the reaction mixture by precipitation in THF and centrifugation. The resulting solution is filtered through celite.

[0108] Mass spectrometry confirms the formation of the amide by fragments 136 and 154 g.mol; other fragments that may correspond to minor co-products are visible at 81, 98, 169 and 196 g.mol1 (see [Fig.3]).

[0109] Monitoring the progress of the transamidation reaction:

[0110] The conversion of benzylamine is measured by NMR spectroscopy with respect to the signal intensity of mesitylene introduced as a standard in the starting solution. - Procedure: A droplet of the reaction mixture is taken and diluted in deuterated tetrahydrofuran (THF) for analysis by NMR spectroscopy. The progress of the reaction is established by the conversion of the benzyl CH2 group, which has a singlet at 3.77 ppm for benzylamine and becomes a doublet at 4.35-4.37 ppm for N-benzyl-formamide. - Results: Total conversion of reactants is observed after a period of 1 hour for a catalyst rate of the invention equal to 5 molar% in the first synthesis (see the NMR spectra in [Fig.4]: before reaction at the top and after reaction at the bottom). At the catalyst rate used in the second synthesis and reduced to 1 molar%, the total conversion of the reactants is observed after a period of 10 hours as well, while it is obtained after a period of 18 hours with massive molybdenum disulfide MoS2. Conclusion: The amount of catalyst and the reaction time required to achieve complete conversion of the reactants with the molybdenum sulfide nanoparticles according to the invention are considerably reduced compared to prior art molybdenum sulfide. Under both conditions, all of the benzylamine is converted in 10 h, thus demonstrating the high efficiency of the catalytic system. Indeed, under these conditions (150 °C), the specific structure of the nanoparticles allows for a faster reaction (10 h) compared to bulk MoS2 (18 h). These results are obtained by reducing the amounts of DMF (5 equivalents) and catalyst (1 mol%) introduced. [YES] Example 3: Preparation of amides by transamidation reaction catalyzed by the MoS2 nanoparticles of the invention

[0112] Several transamidation syntheses catalyzed by molybdenum disulfide nanoparticles prepared according to Example 1 at a rate of 1 molar% relative to the amine were carried out with different amides and different amines. Transamidation conditions

[0113] The MoS2(5 AO) of Example 1, the amine, and the amide in five-fold excess are dissolved in a solvent and poured into a 20 mL tube, which is sealed and heated at 150 °C for 14 hours. The amount of catalyst is fixed at 1 mol% of the number of moles of amine. The other conditions of the protocol are identical to those described in Example 2. Stirring is achieved by refluxing the solvent. - Reaction of aminophenol with acetamide (paracetamol synthesis):# 0.6 mmol of aminophenol and 0.03 mmol of molybdenum disulfide nanoparticles according to Example 1, dissolved in 6.33 mmol of acetamide as a solvent, were used to obtain paracetamol with a conversion rate of 100% after 14 hours of reaction. No byproducts appeared on the NMR spectrum. The MoS2 nanoparticles according to the invention allow for the complete conversion of aminophenol to paracetamol in the presence of acetamide. - Series of syntheses with benzylamine as the amide:# A first series of three syntheses was carried out with benzylamine, choosing formamide, acetamide, or benzamide as the amide. In this series, the conversion rate was greater than or equal to 98%. - Series of syntheses with dimethylformamide as the amide:# A second series of three syntheses was carried out with dimethylformamide, choosing aminophenol, tetrahydroisoquinoline, or dodecylamine as the amine. In this series, the conversion rate was greater than or equal to 96%. - Reaction of phenylamine with formamide:# Finally, a conversion rate of 100% was obtained by reacting phenylamine with formamide. Conclusion#:

[0114] The conversion of the amine to a value greater than or equal to 96%, or even equal to 100%, was obtained with the primary and secondary amines.

Claims

Demands

1. Process for preparing molybdenum disulfide in the form of nanoparticles, said process comprising a reaction step between - a solution of an organometallic molybdenum complex of formula Mo(q6-arene)2 in a first organic solvent, and - a solution of a sulfur donor and at least one ligand, in a second organic solvent.

2. A process according to claim 1, characterized in that the arene is benzene or a benzene molecule substituted by at least one aliphatic alkyl group, saturated or unsaturated, linear or branched, having from 1 to 6 carbon atoms.

3. A method according to claim 1 or 2, characterized in that the sulfur donor is a simple substance of sulfur or a molecule containing one or more sulfur atoms.

4. A method of any one of claims 1 to 3, characterized in that the ligand is a monomeric organic molecule composed of at least one polar function and at least one linear, unsaturated or saturated, branched or cyclic carbon chain, and in that the ligand is capable of engaging a strong or weak bond with molybdenum disulfide.

5. A process according to any one of claims 1 to 4, characterized in that the first solvent and the second solvent are chosen independently of each other from aromatic hydrocarbons such as benzene and toluene, polar solvents such as tetrahydrofuran, and mixtures thereof.

6. A method according to any one of claims 1 to 5, characterized in that the molar ratio between the ligand and the organometallic molybdenum complex is equal to 5.

7. Nanoparticles comprising an inorganic molybdenum disulfide core coated on the surface with at least one ligand, the core having an average hydrodynamic diameter between 1 and 10 nm.

8. A process for the synthesis of an organic compound comprising a reaction step catalyzed by molybdenum disulfide nanoparticles according to claim 7 or obtained according to the process according to any one of claims 1 to 6.

9. A process for synthesizing an organic compound according to claim 8, characterized in that the reaction step is a step of 18 transamidation by reaction of at least one amide and at least one amine.

10. A method for synthesizing an organic compound according to claim 9, characterized in that the organic compound is selected from paracetamol, lidocaine and piperidine.

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