US3214452A - Organometallic compounds - Google Patents

Description

United States Patent 3,214,452 ORGANOMETALLEC COMPOUNDS Robert P. M. Werner, Binningen, Basel-Land, Switzerland, and Harold E. Podall, Arlington, Va., assignors to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed Apr. 23, 1962, Ser. No. 139,292

12 Claims. (CL 260429) This application is a continuation-in-part of applications Serial Nos. 80,542 and 80,543, both filed January 4, 1961, and both now abandoned.

This invention relates to a process for forming novel organometallic compounds. More specifically, the invention relates to a process for forming alkali and alkaline earth metal-etherate salts of Group VB metals in which the metal is present in the form of an anion containing the metal atom having six carbonyl groups bonded to it.

An object of this invention is to provide a novel process for preparing organometallic compounds of Group VB metals. A further object is to provide a process for producing stable alkali metal and alkaline earth metal-etherate salts of vanadium, tantalum, and niobium hexcarbonyl anions. Additional objects will become apparent from the following discussion and claims.

The objects of our invention are accomplished by providing a process in which a reducing metal, which is an alkali metal or an alkaline earth metal, is reacted with a Group VB metal (vanadium, niobium, or tantalum) salt in the presence of an ether solvent and carbon monoxide pressure. The alkali and alkaline earth metal-etherate salts of a Group VB metal-hexacarbonyl anion are prepared by this process. The salts produced from our process are most unusual in that they contain an anion having a charge of minus one in which the negative charge is centered solely on the Grooup VB metal atom. This makes the anion a potent reductant so that it can be readily employed in forming other compounds via an oxidation-reduction type of mechanism.

As set forth above, our process involves reaction between .a reducing metal and a Group VB metal salt in the presence of an ether solvent and under carbon monoxide pressure. The alkali metals which may be employed as reductants are lithium, sodium, potassium, rubidium and cesium. The alkaline earth metals which may be employed are calcium, strontium, barium, and magnesium. In addition, zinc or aluminum may be employed as the reducing metal. Preferably, the reducing metal is an alkali metal and most preferably it is sodium. Also, mixture of the above reducing metals may be employed in our process. As an example, we can employ a mixture of sodium and potassium as the reductant in our process.

The reducing metal employed in our process should be in a highly active form. In the case of the alkali metals this is conveniently accomplished by employing the metal in the fluidized suspension in an inert liquid. Examples of such suspensions are finely divided sodium or potassium in mineral oil or par-afiin. Also, certain of our reducing metals can be placed in a reactive form by amalgamating them. One example of this is a magnesium amalgam. Other forms of activating the reducing metal involve using, for example, freshly prepared metal turnings which employ a large surface area of the freshly cut metal.

The alkali or alkaline earth metal which is employed as a reductant is generally employed in at least a 50 percent excess over that theoretically required to reduce the metal in the Group VB metal salt to a valence state of minus one. Thus, if the Group VB metal salt employed is vanadium trichloride, 4 moles of sodium would be required to reduce one mole of the vanadium reactant. In order to insure that the desired reduction takes place,

3,214,452 Patented Oct. 2%, 1965 Ice however, 6 moles of sodium would generally be employed in the process.

The Group VB metal salt which is employed as a reactant in the process is preferably a metal halide or oxyhalide although other similar salts may be employed if desired. The ether solvent may be a cyclic or straightchain ether and can contain one or a plurality of oxygen ether linkages. Preferably, the ether solvent is a tridentate ether which is to say that it contain-s 3 ether oxygen linkages in the molecule. The tridentate ethers are preferred because the tridentate ether-salts formed from our process are more stable than salts which contain a monodentate or a bidentate ether. As evidence of the great stability of the tridentate ether salts, we have found that sodium bis(diethyleneglycol dimethylether) hexacarbonyl van-adate can be recrystallized from diethylether without solvent exchange between the diethylether and the diethyleneglycol dimethylether.

The ether is generally employed in a large excess since the ether generally functions as both a reactant and solvent. The preferred ethers have low toxicity and are compatible with a wide range of reducing metals. They can be employed in large quantity without the use of elaborate safety precautions. Typical ethers which are representative of those we employ in our process are dibutylether, dioxane, diethyleneglycol dibutylether, ethyleneglycol diethylether, and diethyleneglycol dimethylether. Other ethers such as diethylether can be employed.

As stated previously, our process is carried out under carbon monoxide pressure. Since the time required for reaction is dependent to some degree upon the carbon monoxide pressure, we can conduct the process over a relatively wide range of carbon monoxide pressures using a correspondingly wide range of reaction times. Generally, carbon monoxide pressures ranging from 1,000 to 10,000 p.s.i. may be employed. Preferably, however, the carbon monoxide pressure employed ranges between about 3,000 to about 8,000 p.s.i. since Within this range yields are maximized while reaction time is minimized.

Our process may be carried out over a temperature range from about 60 C. to about 150 C. Higher temperatures than about 150 C. tend to increase the amount of decomposition occurring in the reaction and temperatures lower than about 60 C. tend to increase the reaction time beyond a practical limit. Preferably, our process is carried out at a temperature of about C. since at this temperature, yields are maximized while undesired side reactions are minimized. Generally, our process is carried out with agitation of the reaction mixture since it is found that this insures a more even reaction rate.

As stated previously, the time required for our process is not a true independent variable, but is dependent to some degree upon the other process conditions employed. Thus, for example, if a relatively high temperature, a relatively high carbon monoxide pressure, a high degree of agitation are employed, the reaction time will be reduced. If on the other hand, a relatively low temperature, a relatively low carbon monoxide pressure, and slight agitation are used, the reaction time will be proportionately increased. In practice, the necessary reaction time is easily determined since one can trace the course of the reaction by observing the variation in carbon monoxide pressure in the reaction system. As the reaction proceeds, carbon monoxide is used in the reaction and a substantial pressure drop occurs. When the pressure ceases to drop, this is evidence that the reaction is completed and the reaction product can be discharged. In general, from about one to about 40 hours reaction time is sufficient although, as stated above, other reaction times can be employed if the process conditions are varied accordingly.

Since our process is carried out under carbon monoxide pressure, there is generally no need to employ a protective gas such as nitrogen, helium, argon, krypton or the like in the reaction system. Such gases may be employed, however, if it is desired to increase the pressure without increasing the quantity of carbon monoxide in the reaction vessel.

In conducting our process, the order of mixing the reactants is frequently of some importance. Experiments have demonstrated that some of the Group VB metal salts which are employed as reactants, especially the niobium and tantalum salts, react with the ether solvent to form a product which does not react as readily to form the desired alkali metal or alkaline earth metal-etherate Group VB metal hexacarbonyl salt.

Three experiments were carried out to determine the behavior of tantalum pentachloride with ethers. The first experiment (a) consisted of adding 6.0 parts of TaCl to 90 parts of diethyleneglycol dimethylether (DMC). Experiment (b) consisted of adding 6.0 parts of TaCl to 90 parts of dimethoxyethane (DME). In experiment (c), a like amount of TaCl was added to 90 parts of tetrahydrofuran (THF). All three experiments were carried out under nitrogen. Temperature increments of 5, 6, and 7 C. were noted respectively. The colors of mixtures (a) and (b) were blue-black, while mixture (c) was chalky brown. The mixtures were stirred for two hours and filtered. A grey residue was obtained from (a), while (b) yielded a greater amount of black residue. No residue was obtained when mixture (c) was filtered. The filtrate from (c) was evaporated to dryness and the dry solids were hydrolyzed with H O. The hydrolyzed solids and residues from (a) and (b) were analyzed. Residue (a) contained 38.9 percent tantalum and 30.7 percent chlorine. Residue (b) contained 41.8 percent tantalum and 31.7 percent chlorine. The hydrolyzed solids from (0) contained 17.9 percent tantalum and 10 percent chlorine. Assuming the difference in each case was due to solvent, the results indicate the formation of alkoxides. The alkoxides decrease the availability of the metal. The alkoxide products were:

Residue (a)=TaCl (DMC) Residue (b)=TaCl (DME) Residue (c) =TaCl (THF) These alkoxides are undesired and can be substantially eliminated by carefully observing certain procedures in the mixing of the reactants. In order to diminish this undesirable side reaction, we have found that the Group VB metal reactant should be added directly to the pressurized reaction vessel containing the reducing metal and the ether, both as described previously, and the carbon monoxide under pressure. The Group VB metal reactant is added rapidly and reacts quickly with both the reducing metal and ether to form the desired product before the undesired side reaction can take place. On a relatively small scale, one convenient way of adding the Group VB metal reactant to the reaction vessel is to place it in a sealed vial made of a frangible material. The vial is placed in the reaction vessel along with the other reactants and the vessel is sealed and pressurized with carbon monoxide. The agitation mechanism is then started and the vial is broken when the agitator strikes it so as to quickly release the Group VB metal reactant into the system.

Of the Group VB metal salts we employ in our process, those of vanadium do not tend to react rapidly with the ether solvent. Thus, in the case of vanadium it is not necessary to follow the above procedure in mixing the reactants. In the case of tantalum and niobium reactants, however, it is necessary to follow the above mixing procedure since these compounds have a greater tendency to react directly with the ether solvent.

Of the Group VB metal reactants, certain are preferred for use in our process. The halides, and particularly the chlorides, are preferred reactants since they are relatively cheap and readily available. Examples are the vanadium trihalides, such as vanadium trichloride, tantalum pentachloride, and niobium pentachloride.

The products formed from our process are readily separated from the liquid reaction mixture. The reaction product is generally first filtered to remove any' insoluble residue including any excess reducing metal. After this operation the products are readily precipitated from the filtrate by adding to it a hydrocarbon such as petroleum ether, nonane, hexane, or the like. After the product has precipitated, it can then be separated by means of filtration, decantation of the liquid, centrifugation and the like.

To further illustrate our process, as defined above, there are presented the following examples in which all parts and percentages are by weight unless otherwise indicated.

Example I A mixture comprising 47.2 parts of vanadium trichloride, 41.5 parts of sodium as a 50 percent dispersion in mineral oil and 810 parts of diethyleneglycol dimethylether, which had been distilled over sodiobenzophenone, was charged to a reaction vessel. The reaction vessel was then pressurized to 3,000 p.s.i. with carbon monoxide and heated while agitating the reaction mixture. The reaction mixture was so heated at 100 C. for 20 hours during which time the reaction temperature was raised briefly to 150 C. The reaction vessel was then cooled and vented to relieve the carbon monoxide pressure and the reaction product was discharged. After filtration of the reaction product under a nitrogen atmosphere, petroleum ether was added to the stirred clear yellow filtrate. The resulting oil was triturated with fresh petroleum ether to yield parts of crude yellow solid. This material was soluble in ether, water and acetone and insoluble in petroleum ether. The material was then recrystallized from ether to produce a bright yellow crystalline solid having a melting point of 176 C. with decomposition. The product was relatively stable in air. An aqueous solution of the yellow crystal-material showed an alkaline pH and was strongly reducing. As an example of its reductive properties, the compound was capable of reducing sulfuric acid to hydrogen sulfide in diethyleneglycol dimethylether. On analysis, there was found: C, 42.5; H, 5.52; V, 10.1; Na, 4.68. Calculated for C H NaO V: C, 42.37; H, 5.53; V, 9.98; Na, 4.50 percent. Further, the compound was subjected to magnetic susceptibility measurements and was found to be diamagnetic. The properties, analysis, and infrared absorption spectrum of the compound showed it to be sodium bis(diethyleneglycol dimethylether) hexacarbonyl vanadate, having the empirical formula A sealed glass tube containing 79 parts of tantalum pentachloride was placed in a reaction vessel so that the tube would be broken when the agitator was started. The reaction vessel was charged with 57 parts of sodium (50 percent dispersion) in 720 parts of diethyleneglycol dimethylether. The reaction vessel was closed and pressured to 4,000 p.s.i. with carbon monoxide. A sample of gas from the vessel amounting to 1,000 p.s.i. was vented and analyzed for oxygen. The oxygen content was less than 0.01 percent. The vessel was repressured to 4,000 p.s.i. and heated to C. over night. The total heating time was 23 hours. After that time, the vessel was discharged and rinsed with diethylether. The products were filtered under nitrogen and triturated with petroleum ether. A small yield of sodium bis (diethylene- Example 111 In the same manner as in Example II, 39.0 parts of niobium pentachloride were reacted with 40 parts of sodium in the presence of diethyleneglycol dimethylether solvent. The niobium pentachloride was added to the reaction vessel in a glass tube which was broken after the vessel had been pressurized with carbon monoxide. After heating at 100 C. under a carbon monoxide pressure of 4,000 p.s.i. for about 20 hours, the reaction vessel was discharged. The product was separated from the reaction mixture in the manner employed in Example II. A small yield of sodium bistdiethyleneglycol dimethylether) hexacarbonyl niobate was obtained.

Example IV Vanadium tetrachloride, 193 parts, is charged to a reaction vessel and mixed with 2800 parts of diethyleneglycol dimethylether while cooling the mixture. There is then added to the reaction Vessel 160 parts of sodium in the form of a suspension in mineral oil. T he reaction vessel is pressurized to 5,000 p.s.i. with carbon monoxide while cooling the reaction mixture. The reaction mixture is then agitated at 120 C. for 24 hours after which the reaction vessel is cooled and excess carbon monoxide pressure is released 'by venting. The reaction product is discharged, filtered and petroleum ether is added to the filtrate to give in good yield a precipitate of sodium bisfidiethyleneglycol dimethylether) hexacarbonyl vanadate.

Example V Vanadium oxytrichloride, 210 parts, is mixed with diethyleneglycol dibutylether and charged to a reaction vessel. Two hundred eighty-tour parts of 50-50 sodiumpotassium all-0y suspended :in diethyleneglycol dibutylether is then added to the reaction vessel. The total quantity of diethyleneglycol dibutylether in the reaction vessel is 2010 parts. The reaction vessel is then heated to 110 C. at a carbon monoxide pressure of 4,000 p.s.i. and held at this temperature for 36 hours. The reaction vessel is then cooled; excess carbon monoxide pressure is released by venting, and the reaction product is discharged. On filtration, followed by addition of petroleum ether to the filtrate, an oily recipitate of a mixed sodiumpotassium hexacarbonyl vanadate-diethyleneglycol d-ibuty-lether salt is obtained. This reaction illustrates that ethers having up to about 12 carbon atoms are operable in the process.

Example VI A suspension comprising 200 parts of potassium adrnixed with 2250 parts of dimethoxyethane is charged to a reaction vessel. There is then added 290 parts of vanadium tribromide in a |frangible vial. On charging the reaction vessel with carbon monoxide to a pressure of 5,000 p.s.i., the agitation mechanism is started so as to break the frangible vial and release the vanadium tribromide. The reaction mixture is then heated to 60 C. for hours after which the reaction vessel is cooled, vented, and the reaction product is discharged. On filtration, followed by addition of petroleum ether to the filtrate, a good yield of potassium tris(dirnethoxyethane) hexacarbonyl vanadate is obtained.

Example VII Tantalum pentabromide, 580 parts (enclosed in a frangible vial), 120 parts of amalgamated magnesium and 1800 parts of dioxane are charged to a reaction vessel which is then pressurized to 5,000 p.s.i. with carbon monoxide. The reaction vessel is then heated to 100 C. at which time the agitator is started and the frangible vial is broken so as to release the tantalum penta'bromide react-ant. After heating for 40 hours at 100 C. the reaction vessel is cooled and vented. The reaction product is 6 filtered, petroleum other is added to the filtrate and there is obtained a sticky solid containing a hexacarbonyl tantalate salt.

Example VIII To a reaction vessel containing 210 parts of a mineral oil suspension of sodium and 1800 parts of dimethoxyethane is added 35 8 parts of tantalum pentachloride which is enclosed in a frangible vial. The reaction vessel is then pressurized to 4,000 p.s.i. with carbon monoxide and the vial is broken by starting the agitator. After heating at C. for 36 hours, the reaction vessel is discharged. The product, sodium bis(dimethoxyethane) hexacarbonyl tantala-te, is separated from the reaction product by the procedure used in Example I.

Example IX To a reaction vessel is added 493 parts of niobium pent-abromide enclosed in a frangible vial and 360 parts of a potassium suspension in 2800 part-s of diethyleneglycol dimethylether. The reaction vessel is pressurized to 6,000 p.s.i. with carbon monoxide, heated to C. and agitated. On agitation, the frangible vial is broken and the niobium pentabromide is released into the system. After heating for 30 hours at 110 C. the reaction vessel is cooled and excess carbon monoxide pressure is released by venting. The reaction product is then discharged, filtercd, and petroleum ether is added to the filtrate to produce a precipitate of potassium tris(diethyleneglycol dimethylether) hexacarbonyl niobate.

The compounds produced by our process are quite useful in :metal plating applications. In order to use our compounds in metal plating, they are first converted to a tetraalkylammonium hexacarbonyl Group VB metal salt. This is conveniently accomplished by reacting a tetraalkylammonium compound such as tetramethylammonium bromide with the alkali or alkaline earth metal-etherate salt of the hexacarbonyl Group VB metal anion. As shown previously in Example II, there is obtained from this reaction the tetraalkylammonium hexacarbonyl Group VB metal salt (in that case tetramethylammonium hexacarbonyl tantalate). These salts can be decomposed so as to deposit a metal-containing coating on a surface which it is desired to plate. Since the tetraalkyla-mmonium salts are not volatile, the plating is accomplished by bringing :a heated object, whose temperature is above the decomposition temperature of the tetraalkylammonium salt, into contact With the salt. This results in decomposition of the salt and the formation of a Grou VB metal-containing coating on the heated object.

Another method by which plating can be accomplished is to coat the surface of the object to be plated with the tetraalkylammonium salt of the Group VB metal hexacarbonyl anion and then to heat the coated object to a temperature above the decomposition temperature of the tetraalkylarnmonium salt. This also results in forming a metal-containing coating on the object to be plated.

To further illustrate our method for forming coatings containing a Group VB metal, there is presented the following example.

Example X A glass cloth band weighing one gram is dried for one hour in an oven at C. It is then cover-ed with a thin layer of tetramethylammonium hexacarbonyl tantalate and is placed in a container which is devoid of air. The container is heated to a temperature of 500 C. for one hour after which time it is cooled and opened. The cloth is coated with a tantalum-containing coating, has a metallic grey appearance, and exhibits a slight gain in weight.

As shown by the previous example, the compounds formed from our process can be converted to their tetraalkylammonium salts which can be utilized in forming metal-containing coatings. These coatings are not only decorative but serve also to protect the underlying substrate material from corrosion.

Having fully defined the novel compounds of our invention, their mode of preparation and their utility, we desire to be limited only within the lawful scope or the appended claims.

We claim:

1. A process for the preparation of alkali and alkaline earth metal-etherate salts of a Group VB metal hexacarbonyl anion, said process comprising reacting a reducing metal selected from the class consisting of alkali and alkaline earth metals, with a Group VB metal salt selected from the class consisting of inorganic Group VB metal halides and inorganic Grou VB metal oxyhalides with a saturated, unsubstituted ether selected from the class consisting of monodentate, bi-dentate and tridenta-te ethers having up to about 12 carbon atoms, and carbon monoxide under a pressure between about 3000 to about 8000 psi. and subsequently separating said metal-etherate salt from the resultant reaction mixture by treating said reaction mixture with petroleum ether to remove said metalether-ate salt from solution.

2. The process of claim 1 in which the reducing metal is an alkali metal.

3. The process of claim 2 in which the ether is a saturated, unsubstituted tridentate ether having up to about 12 carbon atoms.

4. The process of claim 3 in which the alkali metal is sodium.

5. The process of claim 4 wherein the tridentate ether is diethyleneglycol dimethylether.

6. The process of claim 5 in which the process is carried out between about 60 C. to about 150 C.

7. The process of claim 6 in which the reaction temperature is about 100 C.

wherein Et. is diethyleneglycol dimethylether and M is a Group VB metal.

12. Organometallic compounds having the formula wherein Et. is a non-cyclic, saturated, unsubstituted tridentate ether molecule having up to 12 carbon atoms, and M is an atom of a Group VB metal.

References Cited by the Examiner UNITED STATES PATENTS 2,870,180 l/59 K-ozikowski et al. 260-429 2,882,288 4/59 Brantley et al 260429 3,060,212 10/62 Brown et al 260-429 FOREIGN PATENTS 1,147,868 6/57 France.

OTHER REFERENCES Vigoureux, Uber gemischte Mono-cyclopenta dienylmetallkomplexe des Vanadins, May 26, 1959.

J.A.C.S., vol. 82, June 5, 1960, pp. 2966 and 2967.

TOBIAS E. LEVOW, Primary Examiner.

Claims (1)

12. ORGANOMETALLIC COMPOUNDS HAVING THE FORMULA