US3404167A - Process for preparing organotin halides - Google Patents

Description

United States Patent 3,404,167 rnocnss FOR PREPARING ORGANOTKN HALIDES Robert D. Gray, Gloucester, and Simon E. Mayer, Lexington, Mass, assignors to Argus Chemical Corporation, Brooklyn, N.Y., a corporation of New York No Drawing. Filed Nov. 30, 1964, Ser. No. 414,841 12 Claims. (Cl. 260-4293) ABSTRACT OF Til-IE DISCLOSURE This invention relates to an improved process for the preparation of organotin compounds, and especially organotin halides. More particularly, the invention pertains to an improved process for the preparation of alkyl or aryl tin halides as well as novel reactants therefor.

One of the methods employed for many years in the preparation of organotin compounds was the direct reaction of metallic tin with alkyl halides. This reaction had certain commercial limitations insofar as it was possible only by utilizing the lower alkyls. Moreover, high yields were only achieved by the use of alkyl iodides, with lower yields resulting even from the use of alkyl bromides. The use of tin alloys in place of the tin is a variation of this basic reaction. The preferred alloy for this purpose was sodium-tin alloys, although more recently magnesium-tin alloys have also been proposed. Prior art teachings indicated that the use of such alloys is limited to those alloys which are sufiiciently brittle to be reduced by grinding operations to a suitable form prior to employment in the process. It has been further found that the use of such alloys or metallic tin, even in the presence of catalysts, leads to progressively lower yields as longer chain length alkyls are employed and as the halides are changed from the iodides to the bromides and then to the chlorides. In fact, for the commercial manufacture of butyl tin halide compounds, which have assumed considerable commercial importance, it has not been economically feasible to use as feed material butyl chloride but only the bromide. Even then the reaction was slow, and the process was severely limited because tin foil had to be used as a source of the tin.

U.S. Patent No. 2,852,543, issued to Blitzer et al. on Sept. 16, 1958, relates to a process for the preparation of alkyl tin chlorides utilizing sodium-tin alloys, and preferably the monosodium tin alloy, NaSn. The Blitzer et al. process requires a reaction temperature of at least 140 C. and pressure conditions to ensure that the alkyl chloride is maintained in a liquid state. The patentees state that the use of a catalyst such as zinc in their process is permissible and frequently desirable. The advantages of the Blitzer et a1. process over the prior art Grignard process and the prior art proposals resulting from the use of sodiun1-tin alloys is discussed in column 1 of US. Patent No. 2,852,543.

One object of the present invention is to provide an improved process for the preparation of alkyl or aryl tin halides which avoids the difiiculties encountered in the prior art processes.

3,404,167 Patented Oct. 1, 1968 Another object of the present invention is to provide an improved process for the preparation of alkyl or aryl tin halides which utilizes a special form metallic tin as one of the reactants.

A further object of the present invention is to provide a process for the preparation of alkyl or aryl tin halides which does not require the specific operating conditions prescribed in certain of the prior art processes.

A still further object of the present invention is to provide novel tin reactants which can be effectively utilized in various reactions such as the preparation of alkyl or aryl tin halides from alkyl or aryl halide feed materials, respectively.

An additional object of the present invention is to provide novel tin reactants which can be reacted with alkyl halides in an improved process to outstanding yields of the desired dialkyl compounds as compared to the trialkyl and tetraalkyl compounds.

These and other objects of the present invention will become readily apparent from the ensuingdescription and the illustrative embodiments.

In accordance with the present invention it has now been found that various alkyl or aryl halides, including alkyl chlorides having relatively long chain lengths, can readily be reacted with tin to produce the desired alkyl or aryl tin halides, provided that the tin is employed in extremely finely divided and oxide-free form. The finely divided tin has to have a particle size ranging from about 1 to 300 microns, and preferably from about 5 to 40 microns. It will be understood that the exact method utilized in preparing the finely divided tin is not a basic feature of this invention. Nevertheless, it has been found that metal spraying methods wherein the tin is atomized are particularly eifective for producing the finely divided tin required in the instant process. It is also preferred to atomize the tin in an inert atmosphere such as helium, argon, or less desirably nitrogen, and the like to avoid surface and internal oxide or other contamination. It is also preferred to maintain the finely divided tin under the inert atmosphere prior to use such as during storage, transfer, etc.

In one aspect of the present invention it has been found advantageous to activate further the reactive finely divided tin particles described above by the use of alkali metals such as sodium, potassium, lithium or mixtures thereof. The preferred alkali metal for this embodiment is sodium. In general, the finely divided tin can be activated by treating the atomized or finely divided tin with an alkali metal under such conditions that the surface of the tin particles is activated and any excess sodium is converted to the sodium-tin alloy. One possible method for accomplishing this surface activation by use of alkali metals involves the use of the fluidized bed technique. Broadly, this technique comprises the agitation of the metal powder in a vertical column by means of an inert gas such as helium or argon. The gas is introduced into the bottom of the column through a porous plate. Both the gas and the walls of the column are heated to a suitable temperature above the melting point of sodium and below the melting point of tin, e.g. C. The required amount of sodium is then introduced slowly, generally in liquid form, preferably into the center of the column so that it is evenly divided over the surface of the metal powder in the column. The sodium cleans and activates the surface of the-tin and any excess sodium present reacts with the latter to form sodium tin alloys. The presence of excess sodium which is not combined as the tin sodium alloy is highly undesirable. It should be understood that such columns can be operated either on a batch or on a continuous basis.

In the activation of the tin particles with alkali metals it is emphasized that only the surface of the tin particles is converted to the sodium-tin alloy; the bulk of the tin remains in the metal form. In some instances it is desirable to obtain further improvements by heating the thus treated finely divided tin particles at temperatures above 100 C., and preferably within the range of about 150 C. to 200 C., for a time period, e.g. at least 2 hours at the lower temperatures and at least minutes at the higher temperatures, to obtain some superficial diffusion of the alkali metal into the bulk of the tin particles in order to eliminate any traces of tin oxide that may be present, and to eliminate alloys of high sodium content from the surface which on reaction with the alkyl halides yield the less desirable trialkyl and tetraalkyl compounds.

The total amount of alkali metal employed in activating the tin particles may range from about 1 to 35% by weight, based on the total weight of the tin particles. For most purposes, however, it is preferred to utilize from about 1 to 5% by weight of the alkali metal; and excellent results have also been achieved when the total amount of alkali metal in the activated tin particles ranges from about 1 to 3%. In accordance with another aspect of the present invention, various methods can be employed to activate the surfaces of the tin particles. For example, the tin may be dispersed as fine particles, in the range of about to 40 microns, into an inert liquid. Other possible techniques which may be used, either alone or in conjunction with different methods, include mechanical abrading, etching, drastic alternate heating and cooling techniques, and similar chemical or physical processes which tend to release the surface strain on the active tin surface. It has been found desirable in some cases to employ an iodine-containing catalyst to initiate the alkylation reaction. Examples of such catalysts include I HgI MgI C HgI, ZnI and the like. Only catalytic amounts of such catalysts need be employed, since it has been found that the amount of catalyst is not an important feature of this invention.

The alkylation process of this invention is generally carried out by reacting an alkyl, aryl or cycloalkyl halide with the finely divided tin or activated tin particles at temperatures of at least about room temperature, preferably about 100 to 200 C., and under pressures ranging from atmospheric to 150 psi. The alkyl halides are preferably the chlorides, bromides, or iodides having alkyl groups containing from 4 to carbon atoms, with a preferred carbon atom range being from about 4 to 8. Examples of such straight or branched chain alkyl halides include the following:

butyl chloride isobutyl chloride sec-butyl chloride tert-butyl chloride butyl bromide butyl iodide pentyl chloride isopentyl chloride tert-pentyl chloride pentyl bromide pentyl iodide Z-ethylhexyl chloride 2-ethylhexyl iodide n-decyl chloride n-dodecyl chloride from 6 to 12 carbon atoms, and illustrative aryl compounds include the following:

chlorobenzene p-dibromobenzene bromobenzene m-diiodobenzene iodobenzene dichlorotoluene chlorotoluene vdibromotoluene bromotoluene diiodotoluene iodotoluene 2-bromonaphthalene o-dichlorobenzene l-chloronaphthalene, etc.

The cycloalkyl halides which may be employed include cyclohexyl bromide, cyclooctyl chloride, and terpene halides.

In general, it is preferred to employ an excess, e.g., at least 50% stoichiometricexcess, of the alkylating agent to produce the desired alkyl or aryl tin halide compounds. It will be understood, however, that either lesser or greater amounts of the tin particles may be employed depending upon the specific reactants, operating conditions, as well as the elaborateness of the recovery equipment.

In some cases it is desirable, although not essential, to employ agitation during the reaction between the alkyl or aryl halides and the finely divided activated tin particles. Agitation may be accomplished by utilizing conventional equipment and procedures.

As noted above, it is also helpful at times to utiliz a catalyst to promote the reaction. This is particularly so when utilizing the finely divided tin particles or the tin particles are activated by a prior treatment with mini mal amounts of an alkali metal.

For some purposes it is also helpful to carry out reaction in an inert solvent. Saturated aliphatic and cyclic hydrocarbon compounds can be employed, and in general it is preferred to use solvents which can be conveniently separated from the products. It is also important to use solvents which are stable under the reaction conditions both to reactants and products. Heptane and isooctane are examples of typical straight and branched chain aliphatic hydrocarbons which have proven to be effective. Cyclohexane, toluene, xylenes, benzene, and diphenyl are typical cycloalkyl compounds, with the former compound being especially preferred. Moreover, various inert ether and ester solvents may also be utilized, including ethyl ether, butyl ether, isobutyl ether, tetrahydrofuran, ethylene glycol diethyl ether, tetramethylene glycol dimethyl ether, diphenyl ether, dimethyl phthalate, di-Z-ethylhexyl phthalate and the like. Polychloro benzenes and polychloro diphenyls may also be used. It is possible, moreover, to operate without the use of an extraneous solvent. Thus, for example, an organotin compound may be used by itself as the reaction medium.

The reaction product mixture obtained from the foregoing process can be subjected to various procedures to recover the desired alkyl or aryl tin halide products therefrom. It is possible, for example, to separate the liquid alkyl or aryl tin halides from the solids present in the reaction product mixture by filtration or centrifugation and to recover the unreacted tin particles. The alkyl tin halide products can be recovered from the separated liquid phase by distilling off solvents at atmospheric pressure and then recovering the various alkyl tin compounds by vacuum distillation. It is also possible to precipitate the products as alkyl or aryl tin oxides, or amine complexes.

More specifically, the recovery procedure can involve the filtration of the solids by means of a Buchner-type funnel and washing the solids with cyclohexane with subsequent distillation on a batch basis to remove the excess alkylating agent and reaction medium followed by cooling to C., and continuation of the distillation process under a vacuum, for example, of l-lO mm. This permits removal of traces of solvent below C. and the recovery and, if desired, separation of the various tin compounds obtained at temperatures in the range of 100-160 C. but generally l30 0, depending on the length of the carbon chain and the halides involved as well as on the degree of vacuum achieved. The product mixture obtained can be fractionated to obtain pure products or, alternatively, reheated to temperatures on the order of 210 C., and if desired with a calculated amount of stannous halide to convert all of the products into a particular alkyl halide.

The solid material can be further treated for recovery of tin values by extraction with water and Washing with dilute acids and alkali to recover any metallic tin by means of subsequent remelting and reatomization operations. From the water soluble portion, halogen values such as bromine or iodine can be recovered by standard methods.

The invention will be more fully understood by reference to the following illustrative embodiments.

EXAMPLE I (A) Finely divided tin free of oxide is prepared by melting tin of 99.99% purity either continuously or in a batch operation and atomizing it at the rate of 50 lbs./ min. through a sonic atomizing nozzle of the type manufactured by Astrosonics Corp. Helium is used as a propellant and the product is recovered by first separating the coarse material by means of a cyclone separator.

The coarse material is then remelted and atomized as described above. The desired material is recovered in suitable filter bags and transferred to the next operation still under a blanket of helium. A typical particle size distribution of such a product is 90% below microns, 70% below 5 microns, and a mean particle size of 3.8 microns.

(B) A 500 gm. batch of finely divided tin produced as set forth in Example I(A), is introduced into a stirred 3 neck flash, the stirrer of which closely follows the side. The flask is continuously purged with a stream of helium. The flask is then heated by means of an oil bath to a temperature of about 100 C. Granulated sodium is now introduced through one of the side arms connected to a container, which is also filled with helium over a period of 10 minutes. The sodium under these conditions evenly coats the tin and reacts with its surface. The material is now heated to 150 C. for 2 hours under an atmosphere of helium with stirring and then allowed to cool.

(C) A 500 mm. batch of finely divided tin produced as set forth in Example I(A) is made into a slurry with commercial heptane and is introduced into a stirred'reactor. To this flask is added a dispersion containing 50 gm. of sodium in 200 gm. of heptane, the dispersion having a grain size finer than 10 microns. The material is stirred for one hour at C. and is then ready for reaction.

EXAMPLE II (A) 300 parts of finely divided tin as produced in accordance with Example I(A) together with 350 parts of butyl chloride, 150 parts of cyclohexane and 1 part of mercuric iodide are introduced into a stainless steel reactor which is then hermetically sealed and heated for 4 hours to a temperature of 100 C. The reactor was cooled and upon recovering the product by filtration and distillation, consisted of 240 parts of alkylatin product, containing on the average 38.5% tin and hence, representing a tin utilization of 31%.

(B) The procedure of Example II(A) was repeated except that 500 parts butyl bromide were substituted for the butyl chloride. The product consisted of 570 parts of alkyltin product containing 31.8% tin and representing a 60.3% tin utilization.

EXAMPLE III (A) 316 parts of the tin reagent prepared in accordance with the procedure outlined in Example I(B) but containing 5% sodium was reacted in a stainless steel reactor with 350 parts of butyl chloride, 150 parts of heptane and one part of zinc iodide at 165 C. for 4 hours, at 130 C. for 4 hours, reheating to 165 C. for 2 hours, yielding 6 05 parts of product, containing 39.7% tin corresponding to a tin utilization of 80%.

(B) 316 parts of tin reagent prepared in accordance with the procedure outlined in Example I(B) but containing 5% sodium was reacted in a stainless steel reactor with 500'parts of butyl bromide, 150 parts of heptane and one part of zinc iodide at 110 C. for 8 hours yielding 575 parts of product containing 31.5% tin and representing a tin utilization of 60.5%.

(C) 316 parts of the tin reagent prepared in accordance with the procedure outlined in Example I(B) but containing 5% sodium was reacted in a stainless steel reactor with 500 parts of chlorobenzene, 150 parts of heptane and one part of zinc iodide at 165 C. for 5 hours yielding 472 parts of product averaging 34.0% tin representing a tin utilization of 53.3%.

(D) 316 parts of the tin reagent prepared in accordance with the procedure outlined in Example I(B) but containing 5% sodium was reacted in a stainless steel reactor with 500 parts of octyl bromide, 150 parts of heptane and one part of zinc iodide at 165 C. for 5 hours yielding 723 parts of product averaging 25.1% tin representing a tin utilization of 60.5%.

(E) The procedure in Example III(A) was repeated except that 500 parts of butyl bromide were substituted for the butyl chloride. The product consisted of 775 parts of butyltin bromide containing 32.9% tin and representing of tin utilization.

The above data demonstrate the effectiveness of preparing alkyl tin halides in accordance with the process of this invention. The preparation of butyl tin chloride is shown in Examples II(A) and III(A), whereas the corresponding butyl tin bromide is shown in Examples II(B) and III(B) and (E). Example III further shows the particular effectiveness of utilizing the sodium activated, finely divided tin particles in the alkylation reaction. The data further reveal that improved tin utilization and product yields can be attained by alternating or cycling the temperatures between 150 to 170 C. and to C., with the temperature being maintained at each range for at least 2 hours.

The alkyl and aryl tin halides which can be prepared in accordance with the improved process of this invention are known to be useful in the preparation of stabilizers for plastics such as vinyl chloride, urethanes, and others, as well as being active constituents in antifouling paints, bacteriostatic agents, and the like.

In addition to being used in the alkylation process described and illustrated above, the finely divided tin particles which have been surface-activated as herein described, are also useful for other purposes such as reactions with water and alcohol to produce organic and inorganic tin compounds such as stannous oxide, stannous hydroxide, stannous chloride, stannous alcoholates, stannous stearates, and the like.

The term alloy as employed throughout this specification and in the appended claims shall mean a mixture or combination of the alkali metal and the tin. As previously set forth, the alkali metal-activated tin particles of this invention are characterized by the formation of alkali metal tin alloys on the surface of the tin particles accompanied by alkali metal diffusion into the body of the tin particle to give an alkali metal concentration gradient from the center of the particle to its outside surface. It is possible, therefore, to refer to the alkali metal-activated tin particles as superficial'diifusion alloys.

While particular embodiments of this invention are shown above, it will be understood that the invention is obviously subject to variations and modifications without departing from its broader aspects.

What is claimed is:

1. A process for the preparation of organotin halides, which comprises reacting an organic halide selected from the group consisting of alkyl, aryl, and cycloalkyl halides with finely divided tin the surface of which is activated by treatment with an alkali metal and having a particle size within the range from about 1 to about 300 microns, in the presence of an iodine-containing catalyst.

2. The process of claim 1 wherein the catalyst is mercuric iodide.

3. The process of claim 1 wherein the catalyst is zinc iodide.

4. The process of claim 1 wherein the reaction is carried out in the presence of an inert solvent.

5. The process of claim 1 carried out at a temperature of at least 100 C.

6. The process of claim 1 wherein the reaction temperature is alternated between about 150 to about 170 C. and about 125 to about 130 C.

7. The process of claim 1 wherein the finely divided tin has a particle size within the range from about 5 to 40 microns.

8. The process of claim 1 wherein the alkyl halide contains from 4 to 20 carbon atoms.

9. The process of claim 1 wherein the alkyl halide is an alkyl chloride.

10. The process of claim 9 wherein the alkyl chloride is butyl chloride.

8 11. The process of claim 1 wherein the alkyl halide is butyl bromide.

12. The process of claim 1 wherein the alkali metal is sodium.

References Cited UNITED STATES PATENTS 9/1958 Blitzer et a1 260-429.7 4/1963 Yatagai et al 260-429] OTHER REFERENCES Karantassis et al.: Academie Des Sciences, vol. 205, (1937), pp. 460-461.

HELEN M. McCARTHY, Primary Examiner.

W. F. w. BELLAMY, Assistant Examiner.