US3332970A - Per (beta and gamma substituted alkylene)mono-and di-tin compounds and the preparation thereof - Google Patents

Description

United States Patent This invention relates to a novel method for the production of organotin compounds and to the novel products thereof. More particularly, it relates to the production of organotin compounds wherein the organic moieties possess functional group substituents.

Numerous examples are available in the art of organotin compounds wherein the tin moiety possesses a multiplicity of hydrocarbyl substituents, for example, tetramethyltin and tetraphenyltin. Little is known, however, of organotin compounds with non-hydrocarbyl organic substituents. Tomilov et al., Zhur. Priklad. Khim., 32, 2600 (1959), report the formation of tetrakis(fi-cyan0- ethyl)tin by electrolysis of strongly basic, concentrated, aqueous solutions of acrylonitrile in the presence of a tin cathode. At a pH of 13-14 and a current density below 2000 amp/m e.g. 200 amp/m2, the tetrakis(fl-cyanoethyl)tin is produced, together with substantial amounts of by-products, particularly bis(,B-cyanoethyl)ether. The yield of B-cyanoethyl tin compound obtained by Tomilov et al. is comparably low, and considerable acrylonitrile is lost through by-product formation, which by-products render more diflicult the recovery of the desired organotin compound. It would be of advantage to provide a more satisfactory method for the production of such organotin compounds.

It is an object of the present invention to provide an improved method for the production of organotin compounds having organic moieties possessing non-hydrocarbyl substituents and the novel compounds produced thereby. A further object is to provide a process for the production of organotin compounds wherein each tin substituent is a non-hydrocarbyl organic moiety. A more particular object is to provide a process for the production of per(,B-cyanoethyl)monoto di-tin compounds and related fi-substituted compounds. A specific object is to provide a process for the production of per(,B-carboxyethyl) monoto di-tin.

It has now been found that these objects are accomplished by the process of electrolyzing aqueous solutions of acrylonitrile in the presence of a tin cathode under controlled conditions of cathode reference potential and basicity of the electrolyte solution, followed by subsequent chemical transformation of the per(/3-cyanoethyl) monoto di-tin product. The process of the invention is adaptable for the production of tetrakis(fi-cyanoethyl)tin and related monotin compounds, or alternatively for the production of the novel hexakis(fi-cyanoethyl)ditin and related ditin products, which production occurs in high yield with little attendant formation of by-products. The B-cyanoethyl tin compounds have been found to be surprisingly resistant to hydrolysis of the carbon-tin or tin-tin linkages, and are readily converted to other novel organotin compounds.

The process of the invention therefore comprises electrolyzing mildly basic aqueous solutions of acrylonitrile under controlled conditions to produce tetrakis(fl-cyanoethyl)tin or alternatively hexakis(;3-cyanoethyl)ditin and subsequently, if desired, performing chemical transformations upon the cyano moieties thereby producing related derivatives.

The electrolyte solution employed in the process of the invention comprises an aqueous solution of acrylonitrile,

3,332,970 Patented July 25, 1967 "ice optionally containing miscible co-solvent, to which has been added sufficient base to render the solution mildly basic. The optimum concentration of acrylonitrile in the electrolyte solution will largerly be determined by the type of product that is desired, as the production of tetrakis(fi-cyanoethyl)tin is favored by comparably high con centrations of acrylonitrile, whereas hexakisUi-cyanoethyl)ditin is the predominant product when comparably low acrylonitrile concentrations are employed. Suitable concentrations of acrylonitrile in the electrolyte solution vary from about 3% by weight to about 30% by weight based upon the total weight of electrolyte solution. For the production of the hexakis(B-cyanoethyl)ditin, acrylonitrile concentrations from about 5% by weight to about 15% by weight on the same basis are preferred, although the formation of tetrakis(B-cyanoethyDtin is preferably accomplished through utilization of electrolyte solutions containing from about 17% by weight to about 25% by weight on the same basis of acrylonitrile.

The principal solvent employed in the electrolyte solution is, of course, water, and it is Within the contemplated scope of the invention, particularly when the ditin product is desired, to employ no additional co-solvent. When higher concentrations of acrylonitrile are desired, as in the production of tetrakis(B-cyanoethyhtin, co-solvent is suitably utilized to increase the solubility of the acrylonitrile in the electrolyte solution. Co-solvents that are satisfactorily utilized are miscible with water, are polar solvents, that is, contain an uneven charge distribution, and are unaffected by the electrolytic reaction conditions as well as being inert to the acrylonitrile reactants and the organotin compounds produced therefrom. Illustrative co-solvents that are suitably employed include ethers such as tetrahydrofuran, dioxane and dioxolane; N,N-dialkyl carboxylic acid amides such as dimethylformamide, diethylformamide, N-methylpyrrolidinone and N,N-dimethylacetamide; and nitriles such as acetonitrile. When co-solvent is employed, amounts of co-solvent up to about 30% by weight of the total electrolyte solution are satisfactory, although concentrations up to about 25% by weight on the same basis are preferred.

It has been found that the control of the pH of the electrolyte solution, defined as the negative logarithm of the molar hydrogen ion concentration thereof, is a critical factor in the process of the invention, particularly with regard to minimizing the formation of by-products. Although the process is operable at a high pH, e.g., over about 9.5, production of larger percentages of undesirable by-products is concomitant with an increase in pH. It is required, however, that the electrolyte solution be basic, that is, have a pH greater than 7. Best results are obtained when the pH of the solution is maintained between about 7.5 and about 9.

The pH of the electrolyte solution is controlled by the addition of base. By the term base as employed herein is meant a material capable of donating an electron pair or alternatively a material whose aqueous solutions have a pH greater than 7. Suitable bases are soluble in water to the extent necessary to give the desired pH, and at the concentrations employed are inert to the acrylonitrile reactant and the products produced therefrom. Typical bases include alkali metal and alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide and barium hydroxide as well as the corresponding oxides, e.g., sodium oxide, calcium oxide and lithium oxide; alkali metal carbonates and bicarbonates such as sodium bicarbonate, potassium bicarbonate, sodium carbonate and lithium carbonate, alkali metal alkoxides such as sodium methoxide, potassium tert-butoxide, lithium isopropoxide and sodium ethoxide; and salts of comparably strong bases and comparably weak acids such as sodium acetate, potassium propionate, tetramethylammonium p-toluenesulfonate, methyltri-n-butylphosphonium naphthalenesulfonate and tetramethylammonium sulfate. The amount of base that is added to the electrolyte solution will be dependent upon the particular base that is employed, as the absolute amount of base is not critical except in so far as it determines the pH of the electrolyte solution. Sufiicient base is added to give the solution the desired pH. Best results are obtained when the base is to be employed is an alkali metal bicarbonate, particularly sodium bicarbonate, and an approximately 5% by Weight aqueous solution thereof gives a suitable pH of about 8.5.

In the electrolysis reaction, the cathode of the electrolysis cell is composed of tin. Although alloys of tin with other metals, particularly less active metals, may be employed it is preferred to utilize a cathode that is substantially pure tin. The anode of the electrolysis cell is not affected by the electrolysis process and therefore is suitably prepared from any convenient inert material capable of conducting the electric current and non-reactive with the aqueous solution. Typical anode materials include platinum, nickel, graphite, tin, lead or the like. Preferred are anodes prepared from platinum or graphite.

The electrolysis process of the invention comprises charging the electrolyte solution to the electrolysis cell wherein the tin cathode and the anode are placed. For purposes of control of the cell reference potential, a standard electrode, typically a saturated calomel electrode (S.C.E.) such as is described in Weissberger, Physical Methods, New York, Interscience Publishers, Inc., 1960, vol. I, Part IV, is introduced into the cell in the vicinity of the cathode and connected to the source of the direct electric current and to the cathode in a conventional manner so that the reference potential of the cathode can be determined. It has been found that the reference potential of the cathode is a critical factor in the production of the B-cyanoethyl tin compounds. During the course of the electrolysis, as acrylonitrile is removed from the electrolyte solution through the formation of organotin compound, the reference potential of the cathode must be increased if a constant current density is maintained. Rather than alter the cathode reference potential to maintain a constant current density, it has been found desirable to maintain a constant cathode reference potential and allow the current to vary if required. In one preferred modification of the process of the invention, however, acrylonitrile is continuously added to the cell to replace that lost by organotin compound formation, and the current density also remains substantially constant. Cathode reference potentials from about 1.6 volt to about 2.0 volts vs. the saturated calomel electrode are satisfactory, although a cathode reference potential of from about l.7 volt to about -l.9 volt (vs. S.C.E.) is preferred.

The electrolysis process is conducted at moderate temperatures, and temperatures that are above the freezing point of the electrolyte solution but below about 50 C. are satisfactory. Best results are obtained when temperatures from about C. to about 40 C. are employed. As the reaction temperature is a factor in determining the solubility of the acrylonitrile in the electrolyte solution, the reaction temperature is a factor in the determination of the major reaction product. When the production of hexakis([3-cyanoethyl)ditin is desired, the lower reaction temperatures, e.g., about 5 C. to C., are suitably utilized, whereas the formation of tetrakis(;3-cyanoethyl) tin is favored by the use of comparably higher reaction temperatures, for example, from about C. to about 30 C.

Subsequent to the electrolysis process, the ,B-cyanoethyl tin compound(s) are separated and recovered by conventional methods such as fractional distillation, selective extraction, crystallization and the like.

The products of the electrolysis procedure are ,tetrakis- (Bcyanoethyl)tin, hexakis(,B-cyanoethyDdi-tin or mixtures thereof, depending largely upon the reaction conditions employed. Generically these products are represented by the formula wherein n has the previously stated significance and X is aminomethyl, halocarbonyl wherein the halogen is halogen of atomic number from 17 to 35, preferably chlorine,

0 (.OR and JNR wherein R is hydrogen or alkyl of from 1 to 8 carbon atoms.

In the above formula, when X represents aminomethyl, the products are per('y-aminopropyl)rnonoto di-tln compounds prepared by reduction of the corresponding [3- cyanoethyl group. The reduction is accomplished by a variety of methods, among which is catalytic reduction with molecular hydrogen. The ,B-cyanoethyl tin compound is contacted with molecular hydrogen in the presence of a hydrogenation catalyst, e.g., a transition metal, particularly a transition metal of Group VIII of the Periodic Table such as nickel, palladium, platinum or rhodium, as well as oxides thereof; or a mixed oxide catalyst such as copper chromite. The catalytic reduction is typically effected in the substantial absence of solvent or in the presence of an inert solvent, e.g., ethers, hydrocarbons and the like, at somewhat elevated temperatures, e.g., from about 50 C. to about 150 C., and preferably at superatmospheric pressures of hydrogen, for example, from about 2 to about 20 atmospheres. An alternative method of effecting reduction of the cyano group to the aminomethyl group comprises the use of a chemical reducing agent such as lithium aluminum hydride, generally as a solution or suspension in an inert, anhydrous diluent which frequently is an ether. By either method, the production of per('y-aminopropyl)monoto di-tin is effected in good yield with little or no carbon-tin or tin-tin cleavage.

The compounds of the above formula wherein X is carboxy are produced by alkaline hydrolysis of the corresponding ,B-cyanoethyl tin compound followed by acidification of the resulting carboxylate salt. Bases that are suitably employed in the alkaline hydrolysis are strong bases, particularly alkali metal and alkaline earth metal hydroxides such as sodium hydroxide, potassium hydroxide calcium hydroxide, barium hydroxide and the like, as well as corresponding alkali metal and alkaline earth metal oxides, e.g., sodium oxide. The hydrolysis is typically conducted in aqueous or aqueousalcoholic solution as by contacting the ,B-cyanoethyl tin compound with an aqueous solution of the base and maintaining the resulting mixture at a somewhat elevated temperature, e.g., from about C. to about C., until reaction is complete. Subsequent to hydrolysis, the product solution is neutralized with any convenient acidic material to liberate the free carboxylic acid.

The per(B-carboxyethyl)monoto di-tin compounds are suitably employed as starting materials for the production of the corresponding acid halides, that is, the com pounds of the above depicted formula wherein X is halocarbonyl. Preferred per (fl-halocarbonylethy1)-monoto '.di-tin compounds are those wherein the halogen is halogen of atomic number from 17 to 35, that is, the middle halogens chlorine and bromine, and particularly preferred are those halocarbonyl compounds wherein the halogen is chlorine. The acid halides are prepared by treating the perQB-carboxyethyDmonoto di-tin compounds with an inorganic acid halide such as thionyl chloride, phosphorus trichloride, phosphorus pentachloride or the like when acid chlorides are desired as the product, or with corresponding inorganic bromides when the production of acid bromides is desired. The reaction is conducted in the presence of an inert reaction medium or alternatively may be effected by merely contacting the p-carboxyethyl tin compound with the inorganic acid halide in the absence of solvent. The reaction is preferably conducted under anhydrous conditions to minimize the hydrolysis of the inorganic reactant or the fl-halocarbonylethyl tin product.

The production of per(fi-carboalkoxyethyl)monoto ditin compounds is achieved by one of several methods. the fl-cyanoethyl tin compounds of the invention are converted to the corresponding ,B-carboalkoxyethyl derivatives by acidic hydrolysis in alcoholic solution. Alcohols preferably employed for ester formation are monohydric alcohols having from 1 to 8 carbon atoms. Best results are obtained when the alcohol employed is an alkanol, particularly a primary alkanol such as methanol, ethanol, propanol, isobutanol, Z-ethylhexanol, n-octanol or the like. The optimum amount of alcohol to be employed will depend upon the functionality of the 6- cyanoethyl tin compound, i.e., whether the tetrakis or the hexakis derivative is employed. Satisfactory results are generally obtained when substantially stoichiometric amounts of alcohol are utilized, that is, a ratio of moles of alcohol to moles of cyano moiety of about 1:1. The hydrolysis and ester formation is catalyzed by small amounts of acid, preferably a strong acid. Exemplary acids include inorganic acids such as hydrochloric acid, phosphoric acid and sulfuric acid; organic acids including sulfonic acids such as p-toluenesulfonic acid and methanesulfonic acid and carboxylic acids such as trichloroacetic acid; and acidic resinous materials known as cationic exchange resins. In an alternate and frequently preferred modification, the p-carboalkoxyethyl tin compounds are produced by reaction of the alkanol with the B-halocarbonylethyl compounds previously described. Such a process is typically conducted by mixing the acid halide derivative and the alkanol, preferably in the presence of a hydrogen halide acceptor, e.g., tertiary amines such as pyridine or triethylamine. The reaction occurs readily at ambient temperature or above. When the production of fl-carbomethoxyethyl tin compounds is desired, a somewhat special situation exists. In addition to the preparative methods previously described, reaction of fl-carboxyethyl tin compounds with diazomethane results in efficient production of the methyl ester. This esterification procedure is customarily conducted in an inert reaction medium, typically an ether such as diethyl ether, dioxane, or tetrahydrofuran. Due to the known reactive character of the diazomethane, the reaction is preferably conducted at room temperature or below, and by adding a solution of diazomethane in the reaction medium in increments to a solution or suspension of the B-carboxyethyl tin reactant.

The compounds of the above-depicted formula wherein X represents the group wherein R has the previously stated significance are amides, and are conveniently produced by reaction of the fl-halocarbonylethyl tin compounds previously described with ammonia to produce amide derivatives wherein both R groups represent hydrogen, with primary amides to produce N-alkylamides wherein one R group represents alkyl of from 1 to 8 carbon atoms, and with secondary amines to produce N,N-dialkylamides. Illustrative amines include methylamine, ethylamine, octylamine, diethylamine, methylhexylamine and the like. The preferred nitrogen-containing reactant is however ammonia as the preferred amide product is per(fi-carbamidoethyl)monoto di-tin.

The products of the process of the invention are useful in a variety of applications. Due to the number of types of functional groups which are produced, a variety of other useful derivatives, e.g., polyamides and polyesters and secondary and tertiary amines may be prepared therefrom. The amino and carboxy derivatives are useful as epoxy curing agents and the organotin compounds are additionally useful as corrosion inhibitors in lubricating oils, anti-knock additives in gasolines and anti-fouling agents for explosives and propellants. Additionally the organotin compounds find utility in the area of agricultural chemicals, particularly as molluscicides.

To further illustrate the novel process of the invention and the novel compounds produced thereby, the following examples are provided. It should be understoodthat the details thereof are not to be regarded as limitations, as they may be varied as will be understood by one skilled in this art.

Example I A cylindrical electrolysis cell of approximately 750 ml. capacity was fitted with a close-fitting cylindrical tin cathode of 200 cm. inside surface area. A platinum anode was supported so that it was concentric with the tin cathode and a reference electrode was placed in the vicinity of the cathode.

The cell was charged with a mixture of 375 ml. of 5% by weight aqueous sodium bicarbonate solution, 125 ml. of acetonitrile and 53 g. of acrylonitrile. The pH of the solution was 8.5. The cathode potential was set at -l.85 volts vs. S.C.E. and the reaction vessel was cooled with water to maintain a temperature below 30 C. At the end of 16 hours, the reaction was terminated and the tin cathode was found to have lost 15.0 g.

The electrolyte solution was extracted with four ml. portions of chloroform. The combined extracts were dried and filtered and then distilled, initially at atmospheric pressure and then at reduced pressure. Gas-liquid chromatographic analysis of the low-boiling components indicated the presence of 18.61 g. acrylonitrile, 4.2 g. of propionitrile as well as acetonitrile and chloroform. Also obtained during distillation were 1.3 g. of bis(ficyanoethyl)ether and 0.7 g. of adiponitrile.

A dark distillation residue of 37.5 g. was obtained which was crystallized by cooling from chloroform to afford 34.1 g. tetrakis(B-cyanoethyDtin, M.P. 22-24 C. This infrared and nuclear magnetic spectra were consistent with the above formula. The conversion of acrylonitrile to tetrakis(,B-cyanoethyDtin was 40.9% and the yield of tetrakis(,B-cyanoethyl)tin was 63% when based upon acrylonitrile converted and 80.2% when based on tin loss from the cathode.

Example II The procedure of Example I was repeated employing ml. dimethylformamide in place of the acetonitrile. The reaction was allowed to proceed 17 hours at which time the weight loss of the cathode was 16.1 g. By a similar work-up procedure, a recovery of 21.4 g. of acrylonitrile was obtained and 33.7 g. of tetrakis( 3-cyanoethyl)tin, which represented a 67.6% yield based upon acrylonitrile converted and a 74% conversion based on tin. The conversion of acrylonitrile to tetrakis(}8-cyanoethyl)tin was 40.4%.

Example III To a cell containing a 50 cm. rectangular (one face) tin cathode and a platinum anode is added 250 m1. of aqueous 0.5 N sodium hydroxide solution and 53 g. of acrylonitrile. A reference electrode was placed in the vicinity of the cathode and a current of 1.0 amp was passed such that the current density on the working face of the cathode was 200 amp/m. throughout the electrolysis. Initially it was found that this corresponded to a potential of 1.2 volt (vs. S.C.E.) although during the course of the electrolysis the reference potential increased to 1.87 volt (vs. S.C.E.). The cross cell voltage was initially 4.2 volts and the reaction temperature was maintained at 10 C.18 C. During the electrolysis, acrylonitrile was added to the electrolyte at a rate of approximately ml./ hr. At the end of 6.5 hours the electrolysis was terminated and the cathode was found to have lost 7.2 g.

The contents of the cell was found to consist of three phases. The upper phase was principally unreacted acrylonitrile, the middle phase was a solution of acrylonitrile in aqueous sodium hydroxide and the bottom layer was a heavy, yellow oil. The whole was extracted with chloroform and fractionally distilled to give, inter alia, 97.8 g. of acrylonitrile, 4.4 g. of propionitrile, 0.35 g. of adiponitrile and 11.6 g. of bis(fi-cyanoethyl)-ether, B.P. 114-117 C. at 1 mm., which was identified by the infrared and nuclear magnetic resonance spectra.

Analysis calc., percent wt.: C, 58.0; H, 6.45; N, 22.6. Found: C, 57.9; H, 6.6; N, 22.1.

Also obtained was a dark residue which upon crystallization from chloroform (Dry Ice cooling), afforded 17.26 g. of colorless crystals, M.P. 2324 0. Infrared and nuclear magnetic resonance spectra indicated the material was tetrakisUi-cyanoethyl)tin.

Analysis calc., percent wt.: C, 43.0; H, 4.48; N, 16.7; Sn, 35.4. Found: C, 42.7; H, 5.0; N, 16.1; Sn, 35.1.

Under the highly basic conditions of this experiment, the yield of organotin based upon acrylonitrile converted was 31.1%. The conversion of acrylonitrile to tetrakis(,B- cyanoethyl)tin was 8.25%.

When the above experiment was repeated employing an initial addition of 132.5 g. of acrylonitrile only, the conversion to organotin compound of the acrylonitrile after 6 hours was 9.8% and the yield of tetrakis (,B-cyanoethyl) tin based on acrylonitrile converted was 31.4%.

When the above experiment was repeated except that a controlled cathode potential of 1.9 volt (vs. S.C.E.) was maintained rather than constant current density of 200 amp/m. the conversion of acrylonitrile to organotin compound after 5 hours was 13.8% and the yield of organotin product, 29.75 g., was 43% based on acrylonitrile converted. The amount of bis(,B-cyanoethyl)ether produced was 9.1 g.

Example IV The procedure of Example I was followed to electrolyze a solution consisting of 320 ml. of 5% by weight aqueous sodium bicarbonate, 80 ml. of dimethylformamide and 212 g. acrylonitrile. At the end of 16 hours, 46.95 g. had been lost by the tin cathode. During the work-up, 83.02 g. of acrylonitrile was recovered and 114.9 g. of tetrakisQS- cyanoethyl)tin was obtained which represented a yield of 73.6% based upon the acrylonitrile converted and a yield of 86.5% based upon the tin lost by the cathode.

Example V The procedure of Example I was followed to electrolyze a solution consisting of 500 g. of 5% by weight aqueous tetramethylammonium p-toluenesulfonate and 53 g. of acrylonitrile. The solution had a pH of 8.5. At the end of 16 hours, the tin cathode weight had decreased 17.8 g. Upon work-up, 16.54 g. of acrylonitrile was recovered and 35.8 g. of tetrakis(,B-cyanoethyl)tin was obtained which represented a 62.1% yield based upon converted acrylonitrile and a 71.1% yield based upon tin. When the concentrated filtrate from the tetrakis(,8-cyanoethyl) tin crystallization was allowed to stand, 1.25 g. of clear crystals of hexakis(,8-cyanoethyl)ditin, M.P. 109-110 C., were obtained.

Exam ple VI In an electrolysis cell similar to that described in Example I, a solution of 550* ml. of 5% by weight aqueous sodium bicarbonate and 53 g. of acrylonitrile was electrolyzed at a reference potential of 1.9 volt (vs. S.C.E.) for 15 hours while the temperature was kept below 15 C. During this time, the tin cathode lost 14.15 g. and solid appeared in the electrolyte. The solid, 9.5 g., was filtered from the electrolyte and set aside.

Subsequent to extraction of the electrolyte solution with four 100 ml. portions of methylene chloride, the low boiling components of the combined extract were removed by distillation. Upon cooling of the residue, an additional 22.1 g. of crystals were obtained which were removed by filtration and also set aside. The filtrate was treated with 25 ml. of benzene and allowed to stand at room temperature for 6 days during which time an additional 4.5 g. of crystals were obtained. The total solids were recrystallized from chloroform to give 32.1 g. of hexakis(,8-cyanoethyl)ditin, M.P. 111.5 C. Evaporation of the benzene from the filtrate gave 4.1 g. of yellow oil, from which 0.86 g. of tetrakisQS-cyanoethyl)tin Was obtained.

The infrared and nuclear magnetic resonance spectrum of the ditin compound were consistent with the above formula.

Analysis calc., percent wt.: C, 38.4; H, 4.28; N, 14.95; Sn, 42.2. Found: C, 38.4; H, 4.3; N, 14.5; Sn, 41.6.

The conversion of acrylonitrile to the ditin compound was 34.4% and based upon the acrylonitrile converted the yield was 70.2%. The yield of hexakis (B-cyanoethyl) ditin based on cathode weight loss was 95.5%.

Example VII The procedure of Example VI was repeated employing 106 g. of acrylonitrile in the electrolyte solution. The weight lost from the cathode was 15.3 g., and upon workup, 20.7 g. of acrylonitrile was recovered. From the product mixture was recovered 2.8 g. of tetrakis (,B-cyanoethyl) tin and 33.4 g. of hexakis(,6-cyan0ethyl)ditin, which represented a yield of 92% based upon the tin lost by the cathode and a 58.7% yield based on acrylonitrile converted.

Example Vlll In ml. of 50% aqueous ethanol containing 7.2 g. (0.18 mole) sodium hydroxide was suspended 10.02 g. (0.03 mole) of tetrakis(fl-cyanoethyDtin. As the mixture was refluxed, ammonia was liberated and the suspended material gradually went into solution. After a reflux period of 5 6 hours, the solution was evaporated under reduced pressure and the remaining cream solid was carefully acidified with 20% hydrochloric acid with ice cooling. The remaining insoluble material was filtered, washed with water and dried at 20 C. at 1 mm. Hg.

The product, tetrakis(,8-carboxyethyl)tin, was obtained as a cream solid, 9.2 g., which had an initial melting point, before and after four recrystallizations from water, of 112-113 C. The infrared and nuclear magnetic resonance spectra were consistent with the above formula. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 35.2; H, 4.8; O, 31.2; Sn, 28.8. Found: C, 34.9; H, 4.8; O, 33.0; Sn, 27.8.

Example IX In 25 ml. of tetrahydrofuran Was suspended 2 g. of purified tetrakis(,B-carboxyethyDtin. An etheral solution of diazomethane was slowly and carefully added to the suspension with occasional stirring. When the reaction was complete as evidenced by cessation of nitrogen evolution, the solvents were evaporated by exposure to a stream of air heated to 40 C. The liquid residue was dissolved in 25 ml. of ether and chromatographed over alumina. Evaporation of the solvent from the eluate afforded 1.9 g. of tetrakis(,G-carbomethoxylethyl)tin, the infrared and nuclear magnetic resonance spectrum of which were consistent with the above formula: The elemental analysis was as follows.

' Analysis calc., percent wt.: C, 41.1; H, 6.0; Sn, 25.4. Found: C, 41.0; H, 6.2; Sn, 24.0.

Example X To g. (0.0122 mole) of tetrakis(B-carboxyethyDtin was added 22.2 g. (0.187 mole) of thionyl chloride. The mixture was placed in a flask and was agitated by the passage of a nitrogen stream, which stream also served to remove the hydrogen chloride formed during reaction. After the reaction had proceeded at room temperature for 24 hours, an additional 11.1 g. (0.0935 mole) of thionyl chloride was added. After 'an additional 24 hours reaction time, a similar addition was made. After a total of 72 hours reaction time, infrared analysis indicated the reaction was complete and the excess thionyl chloride was evaporated to afford 5.4 g. of tetrakis(fl-chlorocarbonylethyl)tin, a tan liquid. The infrared spectrum of the prodnot was in good agreement with that required for the above structure. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 29.8; H, 3.3; Cl, 29.4; Sn, 24.5. Found:.C, 29.1; H, 3.2; Cl, 30.4; Sn, 26.0.

Example XI 'ylethyl)tin. The mixture was allowed to stand overnight at room temperatureand was then evaporated to remove the excess ethanol and pyridine. The residue was dissolved in 20 ml. of methylene chloride and the solution was washed with two ml. portions of 10% hydrochloric acid, three 10 ml. portions of water, and was dried over anhydrous magnesium sulfate. Evaporation of the solvent afforded a light yellow liquid which was dissolved in 20 ml. ether and chromatographed over alumina. Evaporation of the ether from the eluate yielded 1.3 g. of tetrakis(B-carbethoxyethyDtin, a light yellow liquid, the infrared and nuclear magnetic resonance spectra of which were consistent with the above formula. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 45.4; H, 6.8; Sn, 22.8. Found: C, 45.0; H, 6.4; Sn, 21.6.

Example XII To 50 ml. of aqueous ammonia was added 2.5 g. (0.00515 mole) of tetrakis(fl-chlorocarbonylethyl)tin. After standing overnight at refrigerator temperature, the mixture was evaporated to give a solid which was extracted with two 10 ml. portions of ethanol. The extract was filtered and evaporated to give 1.3 g. of tetrakis(,8- carbamidoethyl)tin, a hygroscopic solid. The infrared and nuclear magnetic resonance spectra were in good agreement with those required for the above structure.

Example XIII pressure gave tetrakis(' -aminopropyhtin, a yellow viscons liquid. The infrared spectrum of this liquid was consistent with the above structure. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 41.1; H, 9.15; N, 15.95; Sn, 33.8. Found: C, 40.0; H, 8.9; N, 14.7; Sn, 31.0.

The amine was further characterized as the tetrakis picrate salt by treating a solution of 3.5 g. (0.01 mole) of the tretrakis(' -aminopropyDtin with a saturated solution of 9.2 g. (0.01 mole) of picric acid in 15 ml. of hot ethanol. On cooling and standing at room temperature for one day, crystals were obtained. Recrystallization from 2:1 ethanol-ether afforded yellow crystals, M.P. 156-157", which was the picrate salt of the amine.

Analysis calc., percent Wt.: C, 34.2; H, 3.5. Found: C, 34.4; H, 3.8.

Example XIV A suspension of 2.8 g. (0.005 mole) of hexakis(,6'- cyanoethyl)di-tin in 85% ml. of aqueous ethanol containing 1.2 g. (0.03 mole) of sodium hydroxide was stirred at room temperature for four days. Evaporation of the solvent under reduced pressure gave a white, hygroscopic, glassy residue which was acidified with 10% hydrochloric acid with cooling and the resulting residue was extracted with three 50 ml. portions of acetone. Evaporation of the acetone gave a clear, white gum, a portion of which was crystallized in a 3:1 solution of ethyl acetate-methylene chloride. The product, hexakis- (B-carboxyethyDdi-tin had a melting point of 284-293 C. The infrared and nuclear magnetic resonance spectra were consistent with the above structure. Elemental analysis indicated that the product contained the hexakis(B- carboxylethyl)di-tin.

Example XV In 25 ml. of tetrahydrofuran was dissolved 1 g. of the impure hexakis(fl-carboxylethyDdi-tin product of Example XIV and the solution was treated with excess diazomethane in ether. Evaporation of the solvent gave a yellow liquid which was dissolved in ether and chromatographed over alumina. Evaporation of the solvent from the eluate gave hexakis(fl-carbomethoxyethyl)di-tin, a light yellow mobile liquid. The infrared and nuclear magnetic resonance spectra were consistent with the above structure. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 38.0; H, 5.5; Sn, 32.1. Found: C, 38.8; H, 5.3; Sn, 29.0.

Example XVI A solution of 5.6 g. (0.01 mole) of hexakisQQ-cyanoethyl)di-tin in 200 ml. of tetrahydrofuran was added to a suspension of 3.42 g. (0.09 mole) of lithium aluminum hydride in 250 ml. of tetrahydrofuran. The mixture was stirred at 55 C. for 1 day, cooled and treated with 18 ml. of water. After the mixture was stirred for one hour, the upper layer was removed by decantation and was evaporated under high vacuum to give 3.2 g. of a clear viscous oil which was only sparingly soluble in acetonitrile, dichloromethane and chloroform. The oil was dis solved in methanol and the solution was filtered to remove suspended material. Evaporation of solvent afforded hexakisOy-aminopropyl)di-tin, a clear oil which possessed a characteristic amine odor. The infrared s ectrum was in good agreement with that required for hexakis('yaminopropyl)di-tin. The elemental analysis was as follows.

Analysis calc., percent wt.: C, 37.0; H, 8.2; N, 14.4. Found: C, 38.6; H, 9.1; N, 11.3.

I claim as my invention:

1. The process of producing B-carboxyethyl tin compounds by electrolyzing an aqueous solution of acrylonitrile having a pH from about 7 to about 9.5 in the presence of a tin cathode, said electrolysis being conducted at a cathode reference potential from about 1.6 volt to about 2.0 volt vs. the saturated cal-omel electrode; hydrolyzing the resulting per(/3-cyanoethy1)monoto di-tin by contacting with strong base; and neutralizing the resulting basic solution to afford per(,8-carboxyethyl) monoto di-tin.

2. The process of producing hexakis(B-carboxyethyl) ditin by electrolyzing aqueous acrylonitrile solution having an acrylonitrile concentration from about by weight to about by weight based on total solution and a pH from about 7 to about 9.5, in the presence of a tin cathode, said electrolysis being conducted at a cathode reference potential from about 1.6 volt to about 2.0 volt vs. the saturated calomel electrode; hydrolyzing the resulting hexakis(,6-cyanoethyl)ditin by contacting with aqueous strong base; and neutralizing the resulting basic solution to afford hexakis(fi-carboxyethyl) di-tin.

3. The process of producing ,B-cyanoethyl tin compounds by electrolyzing an aqueous solution of acrylonitrile having a pH from about 7 to about 9.5 in the presence of a tin cathode, said electrolysis being conducted at a cathode reference potential from about 1.6 volt to about -2.0 volt vs. the saturated calomel electrode.

4. The process of producing tetrakis(B-cyanoethyl)tin by electrolyzing aqueous acrylonitrile solution having an acrylonitrile concentration from about 17% by weight to about 25% by weight based on total solution and a pH from about 7 to about 9.5, in the presence of a tin cathode, said electrolysis being conducted at a cathode reference potential from about 1.6 volt to about -2.0 volt vs. the saturated calomel electrode.

5. The process of producing tetrakis(fl-cyanoethyl)tin by electrolyzing an aqueous acrylonitrile solution having an acrylonitrile concentration from about 17% by weight to about 25% by weight based on total solution and a pH from about 7.5 to about 9, at a temperature from about 20 C. to about 30 C., in the presence of a tin cathode and an inert anode, said electrolysis being conducted at a cathode reference potential from about 1.7 volt to about -1.9 volt vs. the saturated calome l electrode.

6. The process of producing hexakis(,B-cyanoethyDditin by electrolyzing an aqueous acrylonitrile solution having an acrylonitrile concentration from about 5% by weight to about 15% by weight based on total solution and a pH from about 7 to about 9.5, in the presence of a tin cathode, said electrolysis being conducted at a cathode 12 reference potential from about -1.6 volt to about 2.0 volts vs. the saturated calomel electrode.

7. The process of producing htixalrisUi-cyanoethyl)ditin by electrolyzing an aqueous acrylonitrile solution havan an acrylonitrile concentration from about 5% by weight to about 15% by weight based on total solution and a pH from about 7.5 to about 9, at a temperature from about 5 C. to about 15 C., in the presence of a tin cathode and an inert anode, said electrolysis being conducted at a cathode potential from about -1.7 volt to about 1.9 volt vs. the saturated cal'omel electrode.

8. Per(fi-X-ethyl)monoto di-tin wherein X is selected from the group consisting of aminomethy-l, halocarbonyl, carboxy, carboalkoxy wherein the alkyl is alkyl of from 1 to 8 carbon atoms, carbamido, N-alkylcarbamido wherein the alkyl is alkyl of from 1 to 8 carbon atoms, and N,N-dialkyl-carbamido wherein the a-lkyls independently are alkyl of from 1 to 8 carbon atoms.

9. Per(,B-carboxyethyl)monoto di-tin.

10. Tetrakis fi-carb oxyethyl) tin.

11. Hexakis(,8-carboxyethyl)di-tin.

12. Per(/3-halocarbonylethyl)monoto di-tin wherein the halogen moiety is halogen of atomic number from 17 to 35.

13. Tetrakis B-chlorocarb onylethyl) tin.

14. Per('y-arninopropyl)monoto di-tin.

15. Tetrakis('y-aminopropyDtin.

16. Hexakis(' -aminopropyl)di-tin.

17. Per(,8-carboalkoxyethyl)monoto di-tin wherein the alkyl moieties are alkyl of from 1 to 8 carbon atoms.

18. Tetrakis(B-carboalkoxyethyDtin wherein the alkyl moieties are alkyl of from 1 to 8 carbon atoms.

19. Tetrakis fi-carb omethoxyethyl) tin.

20. Hexakis(B-cyanoethyl)di-tin.

References Cited Bencowitz: Chem. Abstracts, vol. 54 (1960), page 7374(i).

TOBIAS E. LEVOW, Primary Examiner,

W. F. W. BELLAMY, Assistant Examiner.

Claims (1)

1. THE PROCESS OF PRODUCING B-CARBOXYETHYL TIN COMPOUNDS BY ELECTROLYZING AN AQUEOUS SOLUTION OF ACRYLONITRILE HAVING A PH FROM ABOUT 7 TO ABOUT 9.5 IN THE PRESENCE OF A TIN CATHODE, SAID ELECTROLYSIS BEING CONDUCTED AT A CATHODE REFERENCE POTENTIAL FROM ABOUT -1.6 VOLT TO ABOUT -2.0 VOLT VS. THE SATURATED CALOMEL ELECTRODE; HYDROLYZING THE RESULTING PER(B-CYANOETHYL)MONOTO DI-TIN BY CONTACTING WITH STRONG BASE; AND NEUTRALIZING THE RESULTING BASIC SOLUTION TO AFFORD PER(B-CARBOXETHYL) MONO- TO DI-TIN.