GB1564519A - Method of preparation of chalcogenides - Google Patents

Description

(54) METHOD OF PREPARATION OF CHALCOGENIDES (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly desired in and by the following statement:- This invention relates to the preparation of metal chalcogenides, more especially those of Group IVb and VB transition metals, molybdenum, tungsten and uranium. The Periodic Table employed herein is the Sargent Table on page B-2 of the Handbook of Chemistry & Physics, Chemical Rubber Company, 45th Edn. (1964). Di- and polychalcogenides (MXy wherein M is Ti, Zr, Hf, V, Nb, Ta, Mo and W and Xis S, Se and Te and yis from about 2 to 4) have traditionally been prepared, when preparation was possible at all, by high temperature reactions. The di- and poly-chalcogenides have attracted great interest because of their highly anisotropic properties and intercalation properties. Intercalates made using various chalcogenides are useful as lubricants, battery cathodes and superconductors. (See Gamble et al U.S. Patent 3,766,064). However, a major drawback in the use of chalcogenides is the difficulty encountered in their preparation.

These materials of composition MX2 cannot be prepared in aqueous solution because of the susceptibility of the M+3s4 ,5 ion to hydrolysis or to formation of complex oxo ions (Cotton and Wilkenson, "Advanced Inorganic Chemistry" 2d ed. Interscience, New York, 1966).

It is an object of the present invention to enable the lowcost preparation of a variety of chalcogenides having varied properties, some of which are not obtainable by prior known methods.

According to the invention there is provided a method for the preparation of chalcogenides of the formula MXy wherein M is a transition metal selected from the herein defined Groups IVb and Vb, molybdenum, tungsten and uranium, X is sulfur, selenium or tellurium, and y is from 1.97 to 4;which method comprises reacting, in the absence of aqueous solvent, a salt of said metal M with a source of sulfide, selenide or telluride ions, at a temperature of from -78"C to +400"C.

The process of the invention permits the preparation of finely divided, large surface area, small crystallite diameter, i.e. 0.1 micron (1000 A), preferably less than 0.05 micron (500 A), stoichiometric di- and polychalcogenides.

The preferred anions of the salts of metal M are halide, acetate, carboxylate, perfluorocarboxylate, acetylacetonate or hexafluoroacetonate, the carbonaceous moiety of the organic anion being a C1 to C8 hydrocarbon or fluorcarbon. Preferably said carbonaceous moiety is C1 to C3. Other possible anions are sulfate or nitrate. The preferred anion is chloride. The products of the low temperature nonaqueous precipitation are distinguished from materials prepared by high temperature (greater than 400 C) methods of the prior art by exhibiting markedly different surface area and crystallinity characteristics. A number of compounds of the formula MXy wherein the constituents are as defined above may be prepared via the low temperature nonaqueous disclosed which cannot by synthesized via the of the prior art, i.e. aqueous methods or high temperature methods. VS2 is one such com pound which cannot be prepared by methods common in the prior art. Preferred compounds are TiS2, ZrS2, HfS2, VS2 NbS2, TaS2 and MoS2.

Preferred sources of sulfide, selenide and/or telluride ions are Li2 S, hydrosulfide salts (e.g.

NaHS, NH4HS), (NH4)2 S, Na2 S, U2 Se, Li2 Te, (NH4)2 Se, (RNH3)2 S, (R,R'NH2)2 S, (R,R',R"NH)2S wherein R, R', R" are the same or different and are selected from C1-C20 alkyl (preferably C1 to C8), or C6 -C20 aryl (preferably C6 to C1 2). Preferred nonaqueous solvents are C4 to Cs ethers, acetonitrile, benzonitrile, dimethylformamide (DMF), 1,2-dimethoxyethane, propylene carbonate, aromatics of C6-C20 carbons, preferably C6 to C12, ammonia, molten sulfur, diglyme, sulfur dioxide, ethylacetate, esters of from C4 to C8, sulfolane, tributylphosphate, anhydrous acids for example formic acid and glacial acetic acid, alkyihalides of from C1 to C20, preferably C1 to C5 and arylhalides of from C6 to C20, preferably C6 to C10, pyridine, propionitrile, N-methylformamide, dimethylsulfite, C1 -C30 amines, preferably C1 to C20, C5 -C12 alkanes, preferably C5 -C8.

The solvents of choice are tetrahydrofuran (THF), dimethylformamide (DMF), chlorobenzene, chloroform, pyridine and acetone.

Alternatively, the reaction may be run neat, that is, in the absence of any solvent. The reaction proceeds spontaneously upon mixing in the said temperature range, and at atmospheric pressure. The products may be isolated by filtering, washing with excess solvents or by pumping off the anion salts if they are volatile. In situations wherein the sulfide, selenide and/or telluride ion sources are already solutions, no additional solvent is needed during the course of the reaction although a volume of nonaqueous solvent (i.e.

one which does not offer or accept protons) may be added so as to facilitate product isolation.

The reaction which takes place is nonaqueous MZ4+2A2X MX2; 4AZ solvent or neat M = IVb, Vb or molybendum or tungsten transition metals A = alkali metal, NH4 R,R',R"NH+, R,R'NH2+, or other cation as defined above; Z = convenient anion such as C1, Br, I, acetate, carboxylate, nitrate, etc., as recited above; X = sulfur, selenium or tellurium.

Any convenient source of M+2oM+s, preferably M+4 and M+5 can be used. Complexes formed in solution which can be isolated as solids may be used as M+4 source. In some cases (such as Nb and Ta) a pentavalent salt may be used directly because reduction of M+5 to M+4 occurs, for example: NbCls + 2.5 Li2S o NbS2 J +SLiC1 + 0.5 S The transition metal salts are desirably, although not necessarily, soluble in organic solvents such as THF since it is possible to conduct the reaction neat in all cases. Therefore, solution concentrations are not critical.

The reaction is normally but not necessarily, conducted in the absence of an excess of sulfide, selenide or telluride, although other starting materials may be present in excess.

Since particle size depends on the rate of mixing of reagents, the reaction may be allowed to proceed instantly, upon total admixture of one reagent to the reaction solution yielding fine products or, upon the measured addition of small increments of one reagent to the reaction solution, the reaction not achieving totality for several days.

The temperature of the reaction is preferably 0 to 4000C., more preferably ambient (25"C.) to 3000C. These temperatures are markedly lower than those needed when preparing dichalcogenides via solid state or gas phase methods wherein reaction temperatures up to and exceeding 1000 C. are commonplace.

The products obtained from the low temperature nonaqueous precipitation technique are di- and poly-chalcogenide, particularly di-chalcogenides and more particularly, disulfides, and have unique properties. The products may also be stoichiometric in character. For example, stoichiometric NbS2 is difficult and/or impossible to prepare and stoichiometric VS2 is impossible to prepare by high temperature methods. The particle size and crystallinity of these materials can be greatly varied by practising the preparative methods of the instant invention. Small single crystals or high surface area powders which are amorphous to X-ray (i.e. give no X-ray pattern) can be obtained. Lack of X-ray pattern indicates a crystallite size of less than 0.05 micron (500A). Surface areas can be raised to the point where the di-chalcogenide will remain suspended in solution and homogeneous dispersions created. This effect can be increased by using more polar nonaqueous solvents such as DMF or basic solvents such as pyridine which have a natural tendency to attach to the sulfur layers and cause dispersions. These same solvents are those which tend to intercalate in crystalline transition metal di-chalcogenides.

See Gamble et al, U.S. Patent 3,766,064 for a list of such intercalation materials. Such dispersions can be gelled by proper variation of conditions or adsorbed on basic substrates such as CaO. The materials prepared by the process of the instant invention have utility as electrodes, catalysts, and are useful in the preparation of intercalation compounds which are then useful as lubricants and superconductors.

The above mentioned preparation method allows one to choose compounds from a wide range of particle size, crystallinity and surface area. Solids may be prepared which have the following properties.

A. High surface area, small particle size and amorphous crystallinity. Such characteristics are achieved by use of a solvent which may have the ability to form intercalation complexes with the chalcogenide. Alternatively, chalcogenides formed neat or in the absence of an intercalation solvent may be treated with an intercalate to achieve the same result. Such intercalates may be a strong Lewis base such as pyridine, ammonia, C1 -C20 amines, aldehydes, ketones, amides, heterocyclic bases, amidines, anilines and ethers. The intercalated chalcogenide is then subjected to heat treating, for example at between 75-200"C., with pumping under vacuum when necessary, to drive off the intercalating solvent leaving a high surface area, small particle size, amorphous chalcogenide. Example: TiS2 prepared from THF and treated with pyridine (intercalate pyridine and then drive it out at 1 500C.) gave an amorphous X-ray pattern which indicates a crystallite size of at least less than 0.1 micron and a Brunauer, Emmett and Teller (BET) surface area of 100 m2/gm.

B. Low surface area, small particle size and amorphous crystallinity. Example: The same TiS2 as mentioned in (A) if not treated with pyridine gave an amorphous X-ray pattern and a BET surface area of 10 m2/gm.

C. Low surface area, moderate particle size and high crystallinity. Example: TiS2 prepared from refluxing acetonitrile yielded a TiS2 X-ray pattern. The crystallinity of all materials can further be improved by annealing the Products, suitably at a temperature above 450 C.

D. Homogeneous dispersions: conditions can be arranged as above so that all or part of the dichalcogenides remains in suspension as a homogeneous dispersion. Such materials can be removed by addition of a basic solid such as CaO. Example: TiS2 prepared in propylene carbonate will result in a dark brown opaque dispersion of TiS2 . The TiS2 may be absorbed by shaking the dispersion with CaO which is dark brown when dried. Correspondingly, the original solution is clear after treatment with CaO.

E. High surface area composite: Dichalcogenide/metal oxide solids. Composite materials may be prepared with the di or poWchalcogenide being absorbed on a metal oxide due to the Lewis acid nature of the chalcogenide. Example: The TiS2/Ca0 material mentioned in D above.

F. Gels and Glasses: Gels containing the dichalcogenides may be produced by preparation in certain amines, such as trihexylamine.

The gels produced yield glasses when the solvents are removed. Example: See Example 8.

The precipitation in nonaqueous solution causes the formation of stoichiometric products and effects reactions by virtue of the formation of insoluble precipitates, which reactions are incomplete at higher temperatures in aqueous or solid state systems.

TiS2 may be prepared at from 4500C to 6000C by the reaction in the gas phase of TiC14 and H2S. However, the efficiency of the reaction drops off at lower temperatures because the reaction is reversible.

Thus, H2 S is not a practical sulfiding agent at temperatures less than 400"C.

When the reaction is conducted in nonaqueous solution at low temperature, however, the formation of insoluble precipitates causes the reaction to be irreversible and quantitative to TiS2 . The presence of a chalcogenide salt as an intermediate is important because H2 S bubbled through a solution of RiC14 at room temperature will not produce a reaction. However, if NH3 gas is first bubbled through the solution the passing of H2 S through the ammonia rich solution causes TiS2 to precipitate. This is due to the formation of (NH4)2 S or (NH4)HS as an intermediate and (NH4)Cl is the side product resulting from ion exchange.

Thus, NH3 mediates the reaction although (NH4)2 S is not necessarily actually isolated. If NH3 and H2 S are first coreacted, the intermediate salt is formed.

The product MXy wherein M, X and y are as previously described, withy preferably 2, is separated from the anion salts which are coformed, by filtering and using excess solvent or by pumping off the anion salts if they are volatile. If LiCl is the product anion salt coprecipitated, excess solvent will dissolve it.

If NH4 Cl is the coproduct, pumping under vacuum with remove it (or washing may be used). However, pumping under vacuum may cause sulfur to be removed from the lattice to a greater or lesser extent. For example, VS2 is not stable at higher temperatures. Pumping, as purification, utilized for VS2 at 1 500C will cause sulfur to be removed, which sulfur was supporting the 1:2 stoichiometry of the starting VS2 , thereby providing a route to higher surface area, sulfur-deficient compounds.

If the excess solvent used and coproduct generated in the formation of compounds of the formula MXy are not removed, the combination of the compounds of the formula MXy and the coproducts constituted a battery system in which the coproducts may function as the electrolyte.

Thus, in accordance with an embodiment of the invention a method for the simultaneous production of (i) a cathode of the formula MXy wherein M is a transition metal selected from the herein defined Groups IVb and Vb, molybdenum, tungsten and uranium, X is sulfur, selenium or tellurium and y is from 1.97 to 4, and (ii) an electrolyte; which method comprises: (1) mixing a salt of said metal M with a nonaqueous solvent; (2) mixing the solution of step (1) with a strong acid HY wherein Y is C1 ,Br , I C104 ,PF6 ,BF4 ,orS03CF3 (3) mixing the solution of step (2) with lithium sulfide, selenide, or telluride, at a temperature of from -780C to +4000C, thereby generating the MXy cathode and an electrolyte LiY.

Again, the preferred anions of the salts of metal M are halide, acetate, carboxylate, perfluorocarboxylate, acetylacetonate or hexafluoroacetylacetonate, the carbonaceous moiety of the organic anion being C1 to C8 hydrocarbon or fluorocarbon. Preferably, the said carbonaceous moiety is C1 to C3. Other possible anions are, again, sulfate or nitrate.

Chloride is the most preferred anion.

For example, in a system generating TiS2 as product, the starting materials are TiC14 and a sulfide ion source such as Li2 S. Typically, the electrolyte involves the lithium salt of a strong acid (anion = e PF6, e BF4, e S03 CF3, etc) in an organic solvent such as DME, dioxolane or other ethers or mixtures thereof, the requirement being that the salt has sufficient solubility in the solvent to behave as as good Li' conductor. The Ti+4 salt of the desired electrolytic anion (OPF6, OBF4, eS03CF3, C1 Br, I , Cl 04) is contacted with the Li2 S in the organic solvent to be used in the electrolyte, thus generating TiS2 (to be used in the fabrication of the active cathode) and as coproduct LiY (Y = electrolyte anion) in the organic solvent. By so doing, both the cathodic material and the electrolyte are simultaneously produced. Any contamination of the precipitate (TiS2 in the above discussion) by the solution will not hamper its function, but will enhance it since wetting of the cathode by the electrolyte is desirable.

The invention can be represented by the following equation for the TiC14 system, but it must be recognized that this disclosure is relevant for the other systems described as preparative of compounds of the formula MXy:

TiC14 +4 HY Ii2 S organic TiS2 + 4LiY/ soWen\ organic + HCl cathode electrolyte (Y=oPF6 eBF4 eS03CF3) Treatment of the TiS2 to fabricate a cathode and insertion of an anode (such as Li) will yield a battery.

EXAMPLES All of the preparative work described was carried out either in a dry box or under a blanket of nitrogen. Both the starting metal (+4) and (+5) compounds and the sulfides and selenides thus afforded are sensitive to moisture and oxygen, especially in finely powdered form as results from the heterogeneous precipitation method described. All solvents were dried by standard techniques prior to use, and anhydrous reagents were always employed.

EXAMPLE 1 Preparation of TiS2 (ZrS2, HfS2 ana VS2 The following example employs as a starting material TiC14. It was found that the procedure worked equally well for ZrCl4, HfC14, MoCl4 or VCl4. A solution of 10 millimoles of TiC14 (1 .9g) in tetrahydrofuran (75 ml) was made up in a dry box (TiC14 is not stable in air or moisture) To this stirred solution at room temperature was added 0.96g (20 millimoles) of lithium sulfide. The yellowish solution immediately began to darken. The reaction was allowed to proceed several hours although it was essentially complete within one hour. The resulting dark brown solid was filtered and washed with 10 ml THF. From the combined filtrates 83% of calculated ideal yield of lithium chloride was isolated after evaporation of the solvent. An elemental analysis of the dark brown powder remaining after drying revealed it to be TiS2 containing one-half mole of solvent tetrahydrofuran and less than 5% by weight Lick. The analysis of other compounds prepared is listed below.

The solvent could be removed by warming and pumping. This product was found to absorb a moleequivalent of ammonia in about five minutes (as opposed to days or weeks for TiS2 prepared by conventional means). No x-ray diffraction pattern was seen for the material due to its small crystal size ( < .1 ).

The found BET surface area was about 10 m/ gm which could be raised to about 100 m2/gm by treating with pyridine and filtering and pumping to remove pyridine.

Other solvents which could be substituted for tetrahydrofuran were acetonitrile, propylene carbonate, acetic acid, dimethylformamide (DMF) or no solvent at all (run in excess TiC14), the reaction being run neat. In DMF and propylene carbonate a dispersion resulted in addition to solid.

When sodium sulfide was substituted for lithium sulfide, the reaction required much more time at room temperature and the removal of the side product, sodium chloride from the dark TiS2 was achieved by washing with 12% acetic acid. Alternatively, the sulfide source could be ammonium sulfide (prepared in situ by first adding excess ammonia to a tetrahydrofuran solution of TiCl4 and subsequently bubbling in hydrogen sulfide). The side product in this latter case-ammonium chloride could be removed by sublimation at 1 500C (0.1 torr).

If one wishes to enhance the crystallinity of the product, the dry powder can be partially TABLEI Analyses Ti S Li C1 C H TiS2 (LiC1-3THF)o2s Caic 27.18 36.23 1.00 5.02 20.38 3.39 Found 27.37 36.19 1.27 4.41 16.73 2.93 BET surface area 14.2 m2 lg MoS2 Mo S MOS2A2 (some unreacted 38.37 31.02 Li2S present) NbS2 Nb S NbS197 ratio 36.82 24.89 VS2 V S 4 > VS2.0 27.50 34.70 annealed by heating several days at a temperature of 400 C. or less in an inert atmosphere.

By this process, a product exhibiting the x-ray diffraction pattern typical of TiS2 was obtained.

Yet another means of enhancing the cystallinity of the product is to employ a Soxhlet apparatus whereby the 112S is placed in a thimble over a refluxing solution of TiC14 in tetrahydrofuran. Platelets of TiS2 thus result after several days in the lower solution.

Additional corroboration of the products is found in their (mull) infrared spectra. Thus, for instance TiS2 as obtained by the procedure described in essentially identical to that seen for a sample of TiS2 as obtained from Alfa Inorganics. The latter shows a broad band centered at 400 cam~' due to the Ti-S bond.

The product of TiCl4 and Li2S has a less broad band at 375 cm~l (the breadth is dimished by smaller crystal size).

Example 2 - Preparation of TiS2 (Zr2, HFS2 and VS1) The following example employs as a starting material TiC14. It was found that the procedure worked equally well for ZrC14, HFC14 or VC14. 300 ml of 0.2 M TiCl4 in acetonitrile was slowly added (drop/sec) to a refluxing solution of 0.6 M 112 Sin acetonitrile. The solution was cooled, filtered and washed with methanol to remove the liCl formed. This was then followed by an ether wash and the product dried on a Bucher funnel in a dry box.

The resulting product was goldbrown and gave an x-ray pattern of TiS2 with no further treatment.

Example 3 - Preparation of NbS2 (Ta S2) This procedure is applicable to those transition metals of Group Vb which form pentahalides (Nb and Ta) and the example is given for niobium pentachloride: To a solution of 10 millimoles of NbC15 (2.68 g) in 50 ml tetrahydrofuran was added 1.15 g lithium sulfide (25 millimoles) and the reaction stirred in the dry box overnight. The dark product obtained on filtration was shown to contain 60% by weight NbS197 Example 4 -- Preparation of Molybdenum Disulfide Addition of millimoles of molybdenum tetrachloride and 20 millimoles of lithium sulfide to 30 ml THF with stirring results in a fine black solid which on filtration and drying contains 70% by weight MoS2. Most of the additional weight (60%) can be attributed to solvent which can be removed by heating to ca 1 500C and pumping (1 torr).

Example 5 - Stable Homogeneous Dispersions If the reactions TiC14 + A2 S herein described are carried out in appropriate media, stable homogeneous dispersions of TiS2 in the liquid result (either accompanied by or in the absence of the precipitated solid). For instance, if propylene carbonate (PC) is used as solvent, the supernatant phase will be a dark brown opaque dispersion which is unchanged on filtration (medium frit funnel) and which does not settle out over a period of weeks or months. Alternatively, if in addition to anon- dispersing solvent (such as THF) a dispersing agent such as pyridine (or alkylamines) is initially present, a similar dispersion will result. Murphy and Hull (J. Chem. Phys. 62 973 (1975)) have described dispersions of TaS2 in aqueous media which are considerably less stable due to eventual decomposition of the sulfide by water (hydrolysis). In non aqueous solutions such as those described in the instant invention such decomposition does not occur and stability remains for months.

The reaction of a solution of TiC14 in excessive trihexylamine and tetrahydrofuran with hydrogen sulfide provides another example of a means of dispersing the product TiS2 in the media. The presence of the amine in the reaction milieu serves to disperse the extremely fine particles of the product. The dichalcogenides formed in such dispersions may adsorbed on high surface area carbons. refractory oxides and high surface area basic or acidic solids such as CaO, MgO, A1203 silica-alumina, the solution clearing the time.

Example 6 - Metal-Rich Products for V and Nb Attempts to prepare stoicniometnc disulfides of vanadium and niobium via high temperature ( > 4000C) techniques result in metalrich products due to the vapor pressure of sulfur at elevated temperatures. By using the ambient temperature method described in this invention, essentially stoichiometric 2:2 sulfur to metal products result. Evidence (besides verifying analysis) is found in the behavior of our products on heating to 1000C. In this situation sulfur is evolved and can clearly be visually perceived on the cooler parts of the tubes.

Example open Circuit Voltage of TiS7 Electrode 1 gram of TiS2 prepared in THF by the instant process was pressed into an aluminum grid to make a cathode. The open circuit voltage of this cathode was measured against Li in a IiC104/THF/DME electrolyte and gave a value of 2.55 v and discharged to give 1 ,80 v and could be recharged. These voltages correspond to TiS2 (2.55 v) and LiTiS2 (1.80 v) further proof of the TiS2 composition.

Example 8 - TiS2 Gel and Glass Formation To 40 mmol trihexylamine in 25 ml tetrahydrofuran, 10 mmol TiC14 was added. Then anhydrous hydrogen sulfide was sparged into the solution at a flow rate of about 1-5 cc/sec for five minutes. In the course of this addition, the solution became dark and somewhat more viscous. After the addition, the dark mixture was allowed to sit at room temperature overnight, resulting in a black gel which, if pumped and heated to greater than 300"C yielded a black glassy solid having no x-ray powder diffraction pattern. Scanning electron microscopy (SEM) verified that the product was a glassy phase, and x-ray fluorescence analysis showed titanium and sulfur.

Example 9 - Ammonia Uptake The transition metal dichalcogenides are known to absorb ammonia to form 1:1 products (U.S. Patent 3,766,064, F.R. Gamble, R.A. Klemm and E.F. Ullman). The rate of this reaction depends on the surface area of the solid dichalcogenide (if ammonia vapor at ambient conditions is used). For instance, 100 mesh (Tyler series) TiS2 requires several days to react completely with ammonia. The TiS2 prepared by the method outlined in Example 1, when contacted with ammonia vapor under ambient conditions in a gas buret, absorbed one mole within five minutes (no more was picked up).

Example 10 - Reaction with n-Butyllithium A general reaction of the Group IVb an

Rate Constants NbS12 - Wepared from elements K = 8.7 x gm ' sec NbS? - repared from above K=13x101 gm ' sec TiS2 in Group IVb is more active prepared in the instant manner than by bulk methods. Also, VS2 in Group Vb was active as a catalyst. VS2 cannot be prepared in bulk by previously known methods as stated above.

Example 13 - Formation of an Intercalation Complex Directly Ordinarily, using large crystal size transition metal dichalcogenides prepared by other means, sterically restricted amines such as 4-t-butyl- pyridine cannot intercalate between the layers and form inclusion compounds (Gamble et al, Science Vol. 174,pg493,1971). However, if during the precipitation reactions described hx rin, such molecules are present, they will be included in the solid product which forms in situ. As an example, if5 mmol of 4-tbutyl- pyridine is present in the THF solution when 10 mmol of TiS2 is prepared via TiCl4 and U2 S, the product, a dry dark solid powder, will contain the amine.

Example 14 - Pre ration of US2 under Ambient Conditions (in Drybox) A green solution was made up containing 3.70g of UC14 (10 mmoles) in 100 ml THF. To this solution was added 0.92g (20 mmoles) U2 S with stirring. The color darkened to brown and the reaction was stirred a day at room temperature. On filtering, washing with 20 ml THF and drying of the precipitate 3.07g black powder (102% yield) resulted. An x-ray diffraction of this product showed no reflections due to the fine particle size.

In "Handbook of Preparative Inorganic Chemistry" V.2 (second edition) edited by G. Brauer (Academic Press, 1965) on page 1446 is detailed the typical preparation of US2 (from UCl4 + H2 S) at 600--700-.

Example 15 - U2 Se + ZrC14, ZrSe2 Into 50 ml acetonitrile, 10 millimoles zirconium tetrachloride is added and then, with stirring 20 millimoles of lithium selenide is added portionwise. After allowing to stir several hours, the solid product is collected on a filter and washed with acetonitrile and dried. Thus, 10 millimoles of zirconium diselenide is afforded.

Example 16 - Polysulfide Preparation Polysulfide may be prepared by adding the proper stoichiometric amount of sulfur with the Li2 S, as in the previous examples, to yield the appropriate U2 S- for the desired reaction. Two examples of the preparation of known polysulfides are shown below: VC14 +2LI2S2 o VS4 t + 4LiC1 TiC14 + li2 S2 + Ii2 S o TiS3 + + +4IiC1 However, this method is not limited to known polysulfides but is a route to previously unknown polysulfides such as TiS4, TaS6 etc.

This method also yields dispersions, gels, etc. of these materials whose properties will not be governed by the chainlike morphology of the polysulfides.

Example 17 - Neat Preparation of Crystalline TiS2 from NH3, H2 Sand TiCl4 T . .1 1 J I into a three-necked flask, a quantlty ot (approximately 5 grams) of (NH4)HS or (NH4)2 S was prepared by flowing in NH3 gas and H2 S gas. To the resulting white solid 3.8 gms of TiCl4 (20 mmol) was added dropwise. A reaction immediately occurred yielding a blackbrown solid, which was TiS2 + (NH4)Cl. This black-brown solid was removed from the flask and sealed in vacuum in a 20 mm diameter quartz tube which was 25 in.

long. The tube was placed in a temperature gradient with one end at 3800C and the other at 100 C. for one day. (NH4)C1 sublimed and condensed at the colder end thus effecting separation. At the hot end, the TiS2 annealed yielding a perfect crystalline X-ray powder pattern.

WHAT WE CLAIM IS: 1. A method for the preparation of chalcogenides of the formula MXy wherein M is a transition metal selected from the herein defined Groups IVb and Vb, molybdenum, tungsten and uranium, X is sulfur, selenium or tellurium, andy is from 1.97 to 4; which method comprises reacting, in the absence of aqueous solvent, a salt of said metal M with a source of sulfide, selenide or telluride ions, at a temperature of from -780C to +4000C.

2. A method as claimed in claim 1, wherein the product chalcogenide is isolated and the isolated product is annealed at a temperature of over 450 C, thereby generating a product having a low surface area, moderate particle size and high crystallinity.

3. A method as claimed in claim 1, wherein the product chalcogenide is isolated and the isolated product is contacted with an intercalating solvent, thereby forming an intercalated chalcogenide, from which the solvent is subsequently driven off by means of heat, thereby generating a chalcogenide of increased surface area.

4. A method as claimed in claim 3, wherein the intercalating solvent is selected from pyridine, ammonia, C1 to C30 amines, aldehydes, ketones, amides, heterocyclic bases and amidines, and the solvent is subsequently driven off at a temperature of between 75-200 C.

5. A method as claimed in any preceding claim, wherein the temperature of reaction is between 25 to 3000C.

6. A method as claimed in any preceding claim, wherein the source of sulfide, selenide

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. Rate Constants NbS12 - Wepared from elements K = 8.7 x gm ' sec NbS? - repared from above K=13x101 gm ' sec TiS2 in Group IVb is more active prepared in the instant manner than by bulk methods. Also, VS2 in Group Vb was active as a catalyst. VS2 cannot be prepared in bulk by previously known methods as stated above. Example 13 - Formation of an Intercalation Complex Directly Ordinarily, using large crystal size transition metal dichalcogenides prepared by other means, sterically restricted amines such as 4-t-butyl- pyridine cannot intercalate between the layers and form inclusion compounds (Gamble et al, Science Vol. 174,pg493,1971). However, if during the precipitation reactions described hx rin, such molecules are present, they will be included in the solid product which forms in situ. As an example, if5 mmol of 4-tbutyl- pyridine is present in the THF solution when 10 mmol of TiS2 is prepared via TiCl4 and U2 S, the product, a dry dark solid powder, will contain the amine. Example 14 - Pre ration of US2 under Ambient Conditions (in Drybox) A green solution was made up containing 3.70g of UC14 (10 mmoles) in 100 ml THF. To this solution was added 0.92g (20 mmoles) U2 S with stirring. The color darkened to brown and the reaction was stirred a day at room temperature. On filtering, washing with 20 ml THF and drying of the precipitate 3.07g black powder (102% yield) resulted. An x-ray diffraction of this product showed no reflections due to the fine particle size. In "Handbook of Preparative Inorganic Chemistry" V.2 (second edition) edited by G. Brauer (Academic Press, 1965) on page 1446 is detailed the typical preparation of US2 (from UCl4 + H2 S) at 600--700-. Example 15 - U2 Se + ZrC14, ZrSe2 Into 50 ml acetonitrile, 10 millimoles zirconium tetrachloride is added and then, with stirring 20 millimoles of lithium selenide is added portionwise. After allowing to stir several hours, the solid product is collected on a filter and washed with acetonitrile and dried. Thus, 10 millimoles of zirconium diselenide is afforded. Example 16 - Polysulfide Preparation Polysulfide may be prepared by adding the proper stoichiometric amount of sulfur with the Li2 S, as in the previous examples, to yield the appropriate U2 S- for the desired reaction. Two examples of the preparation of known polysulfides are shown below: VC14 +2LI2S2 o VS4 t + 4LiC1 TiC14 + li2 S2 + Ii2 S o TiS3 + + +4IiC1 However, this method is not limited to known polysulfides but is a route to previously unknown polysulfides such as TiS4, TaS6 etc. This method also yields dispersions, gels, etc. of these materials whose properties will not be governed by the chainlike morphology of the polysulfides. Example 17 - Neat Preparation of Crystalline TiS2 from NH3, H2 Sand TiCl4 T . .1 1 J I into a three-necked flask, a quantlty ot (approximately 5 grams) of (NH4)HS or (NH4)2 S was prepared by flowing in NH3 gas and H2 S gas. To the resulting white solid 3.8 gms of TiCl4 (20 mmol) was added dropwise. A reaction immediately occurred yielding a blackbrown solid, which was TiS2 + (NH4)Cl. This black-brown solid was removed from the flask and sealed in vacuum in a 20 mm diameter quartz tube which was 25 in. long. The tube was placed in a temperature gradient with one end at 3800C and the other at 100 C. for one day. (NH4)C1 sublimed and condensed at the colder end thus effecting separation. At the hot end, the TiS2 annealed yielding a perfect crystalline X-ray powder pattern. WHAT WE CLAIM IS:

1. A method for the preparation of chalcogenides of the formula MXy wherein M is a transition metal selected from the herein defined Groups IVb and Vb, molybdenum, tungsten and uranium, X is sulfur, selenium or tellurium, andy is from 1.97 to 4; which method comprises reacting, in the absence of aqueous solvent, a salt of said metal M with a source of sulfide, selenide or telluride ions, at a temperature of from -780C to +4000C.

2. A method as claimed in claim 1, wherein the product chalcogenide is isolated and the isolated product is annealed at a temperature of over 450 C, thereby generating a product having a low surface area, moderate particle size and high crystallinity.

3. A method as claimed in claim 1, wherein the product chalcogenide is isolated and the isolated product is contacted with an intercalating solvent, thereby forming an intercalated chalcogenide, from which the solvent is subsequently driven off by means of heat, thereby generating a chalcogenide of increased surface area.

4. A method as claimed in claim 3, wherein the intercalating solvent is selected from pyridine, ammonia, C1 to C30 amines, aldehydes, ketones, amides, heterocyclic bases and amidines, and the solvent is subsequently driven off at a temperature of between 75-200 C.

5. A method as claimed in any preceding claim, wherein the temperature of reaction is between 25 to 3000C.

6. A method as claimed in any preceding claim, wherein the source of sulfide, selenide

or telluride ions is selected from 1i2 S, hydrosulfide (HS) salts, (NH4)2 S, Na2 S, Li2 Se, U2 Te,(NH4 )2 Se. (RNH3 )2 S, (RR'NH2)2 Sand (RR'R"NH)2 S, wherein R, R' and R" are the same or different and are selected from C1 to C20 alkyl and C6 -C20 aryl groups.

7. A method as claimed in any preceding claims. wherein a non-aqueous solvent is present in the reaction.

8. A method as claimed in claim 7. wherein the nonaqueous solvent is selected from aceto nitrile. benzonitrlle. propionitrile, acetone, C1 - C20 alkyl halides, C6 -C20 arylhalides. 1,2-di- methoxyethane, diglyme. N-methylformamide, dimethylformamide, aromatics of C6 -C20 carbons, pyridine, sulfolane, tributyl phosphate, C5 to C12 alkanes, C4 -C8 ethers and esters, anhydrous acids. dimethyl sulfite and C1 to C30 amines.

9. A method as claimed in claimS, wherein the anhydrous acids are formic acid and glacial acetic.

10. A method as claimed in any one of claims 1 to 6. which comprises generating dior poly chalcogenides in the presence of intercalating agents wherein said intercalating agent is initially present in the reaction mixture as a solvent.

11. A method for the simultaneous production of (i) a cathode of the formula MXy wherein M is a transition metal selected from the herein defined Groups IVb and Vb. molybdenum, tungsten and uranium, X is sulfur, selenium or tellurium andy is from 1 97 to 4, and (ii) an electrolyte; which method comprises: (1) mixing a salt of said metal M with anon- aqueous solvent; (2) mixing the solution of step (1) with a strong acid HY wherein Yis C1, Br I, C104, PF6, BF4, or S03CF3; (3) mixing the solution of step (2) with lithium sulfide, selenide, or telluride, at a temperature of from -78"C to +400 C, thereby generating the MX cathode and an electrolyte liY.

12. A method as claimed in any preceding claim, wherein the anion of the salt of metal Mis halide, acetate, carboxylate, perfluorocarboxylate, acetylacetonate or hexafluoroacetylacetonate, the carbonaceous moiety of the organic anion being a C1 to C8 hydrocarbon or fluorocarbon.

13. A method as claimed in any preceding claim and substantially as herein described.

14. A method as claimed in claim 1 and sub stantially as herein described with reference to any one of Examples 1 to 6, 8 and 13 to 17.

15. The chalcogenide product of the method claimed in any one of claims 1 to 14.

16. An homogeneous dispersion, obtained by the method claimed in any one of claims 7 to 9, of TiS2, VS2, ZrS2, HfS2. NbS2. TaS2 or MoS2.

17. A composition comprising an homogeneous dispersion claimed in claim 1 6 deposited on a high surface area support, said support being high surface area carbon or a high surface area refractory oxide.