METHOD FOR CLEAVING ALKYL TIN HALIDES

Abstract

A method of producing a mono alkyl tin halide from a poly alkyl tin halide, comprising providing the poly alkyl tin halide, adding a Lewis acid catalyst to the poly alkyl tin halide to create a reaction mixture, heating the reaction mixture, dosing a hydrogen halide into the reaction mixture to convert the poly alkyl tin halide into a raw product containing mono alkyl tin halide.

Claims

1. A method of producing a mono alkyl tin halide from an alkyl tin compound, the method comprising: providing the alkyl tin compound; adding a Lewis acid catalyst to the alkyl tin compound to create a reaction mixture; heating the reaction mixture; and dosing a hydrogen halide into the reaction mixture to convert the alkyl tin compound into a raw product containing mono alkyl tin halide.

2. The method according to claim 1, wherein the Lewis catalyst comprises a covalent metal halide and a Lewis active metal center.

3. The method according to claim 2, wherein the covalent metal halide comprises at least one of Fluorine, Chlorine, Bromine and Iodine.

4. The method according to claim 2, wherein the Lewis active metal center is one of tin, titanium, aluminum, iron, boron, bismuth, silicon, and phosphor.

5. The method according to claim 1, wherein the Lewis catalyst used is aluminum chloride (AlCl.sub.3).

6. The method according to claim 1, wherein the Lewis catalyst is being used in an amount between 0.1 weight % and 10 weight % based on the alkyl tin compound.

7. The method according to claim 6, wherein the Lewis catalyst is being used in an amount between 2 weight % and 6 weight %.

8. The method according to claim 1, wherein an aprotic or inert solvent is added to the reaction mixture.

9. The method according to claim 8, wherein the solvent is at least one of an alkane, an aromatic, a halogenated aromatic, n-octane, toluene, o-xylene and 1,2-dichlorbenzene.

10. The method according to claim 1, wherein the reaction mixture is heated to a temperature in one of the ranges: from 100° C. to 160° C., from 115° C. to 145° C., and from 135° C. to 140° C.

11. The method according to claim 1, wherein the hydrogen halide used is hydrogen chloride (HCl).

12. The method according to claim 1, wherein the hydrogen halide used is gasiform.

13. The method according to claim 1, wherein the hydrogen halide is used neat anhydrous.

14. The method according to claim 1, wherein the hydrogen halide is fed into the reaction mixture over one of the following periods: 1 hour to 20 hours, 3 hours to 10 hours, and 4 hours to 8 hours.

15. The method according to claim 1, wherein the alkyl tin compound is at least one of a poly alkyl tin halide and a tetra alkyl tin.

16. The method according to claim 1, wherein the alkyl tin compound is dealkylated into mono alkyl halides according to one of the equations: ##STR00006## wherein R is one of an Alkyl and Cylcoalkyl, X is one of Chlorine, Bromine and Iodine and CatX.sub.n is the Lewis acid catalyst.

17. The method according to claim 1, wherein the alkyl tin compound is reacted with tin tetra halide and the resulting mixture is dealkylated into mono alkyl halides according to one of the equations: ##STR00007## wherein R is one of an Alkyl and Cylcoalkyl, X is one of Chlorine, Bromine and Iodine and CatX.sub.n is the Lewis acid catalyst.

18. The method according to claim 15, wherein the mono alkyl tin halide monobutyltintrichloride (MTBTCl.sub.3) is produced from one of dibutyltindichlorid (DBTCl.sub.2), tributyltinchloride, and tetrabutyltin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention relates to a way for producing mono alkyl tin halides from alkyl tin compounds, e.g. poly alkyl tin halides. For this purpose, a cleavage reaction according to formula (7) is employed.

R.sub.2SnX.sub.2+HX.fwdarw.RSnX.sub.3+RH   (7) [0041] R=Alkyl, Cylcoalkyl [0042] X=Cl/Br/I

[0043] This process is enabled by utilizing a Lewis acid catalyst and leads to a reaction mechanism shown in formula (8). Without catalyst no reaction occurs.

R.sub.2SnX.sub.2+CatX.sub.n.fwdarw.RSnX.sub.3+RCatX.sub.n−1   (8)

RCatX.sub.n−1+HX.fwdarw.CatX.sub.n+RH   (9) [0044] R=Alkyl, Cylcoalkyl [0045] X=Cl/Br/I [0046] CatX.sub.n=catalyst

[0047] The catalyst for this reaction is chosen from the known Lewis acid catalyst series. The catalyst comprises covalent metal halides taking the halides F/Cl/Br/I and Lewis active metal centers into account, for example Sn/Ti/Al/Fe/B/Bi/Si/P, in particular Sn and Al. The amount of catalyst being used may be between 0.1 weight % and 10 weight % based on the alkyl tin compound, e.g. the poly alkyl tin halide or tetra alkyl tin, in particular between 2 weight % and 6% weight %.

[0048] The reaction may be conducted with or without the use of a solvent, wherein an aprotic or inert organic solvent may be preferred. This includes alkanes, aromatics and halogenated aromatics, for example n-octane, toluene, o-xylene, 1,2-dichlorbenzene.

[0049] The conversion is done at elevated temperatures in a range from 60° C. to 220° C., for example 100° C. to 150° C., in particular 125° C. to 140° C.

[0050] The hydrogen halides employed in this reaction are used neat anhydrous and are fed into the reaction mixture within a time period of 1 h to 20 h, for example within 3 h to 10 h, in particular 4 h to 8h.

[0051] The alkyl tin compounds, e.g. poly alkyl tin halides or tetra alkyl tin, utilized as raw materials can be dealkylated into mono alkyl halides according to equations (10)(11)(12), the conversion of di alkyl tin halides into mono alkyl tin halides according to equation (12) is the preferred reaction.

##STR00003##

[0052] An exemplary embodiment is the use of mono- and dialkyl tin halide mixtures as resulting from catalyzed redistribution procedures. For that purpose, alkyl tin compounds, e.g. poly alkyl tin halides or tetra alkyl tin, are reacted with tin tetra halide into corresponding mixtures and subsequently dealkylated using the same Lewis acid catalyst as shown in equation (13) (14). This operation may be conducted in the same reaction vessel. It has been shown that the use of Lewis acid catalyst significantly enhances the speed of the redistribution reaction.

##STR00004##

[0053] Resulting alkane cleavage products are formed in liquid or gaseous state in the reaction mixture. The purification of the mono alkyl tin halides is conducted by state-of-the-art distillation resulting in up to 90% yield based on used alkyl tin compounds, e.g. poly alkyl halides or tetra alkyl tin.

[0054] Reductive elimination (15) (16) was seen to form <10% stannous halides.

##STR00005##

EXAMPLES

[0055] Preparation of Monobutyltintrichloride from Dibutyltindichloride

[0056] In a round bottomed flask 300 g Dibutyltindichloride technical grade (GC derivative with EtMgBr showed 95.0% purity) 0.98 mol was mixed with 9.0 g anhydrous Aluminium chloride 0.067 mol and heated under nitrogen atmosphere to 130° C. to 140° C. A stream of thoroughly dried hydrogen chloride was inserted with approximately 6 l/h while maintaining the temperature of the mixture. Effluent gas was neutralized and alkanes trapped in a cold trap. After 6 h the conversion was completed as seen in a GC measurement (EtMgBr MBTC 99.5%). The resulting mixture was distilled at 7 mbar to yield 270 g colorless MBTC b.p. 88° C. (GC content EtMgBr>99.5 and 30 g dark residue (tin 23.8%; aluminium 8.47%; chloride 24.8%).

[0057] Preparation of Monobutyltintrichloride from Tributyltinchloride

[0058] In a round bottomed flask 170 g Tributyltin chloride technical grade (GC derivative EtMgBr showed TBTC 94.47%) was mixed with 9.0 g anhydrous Aluminium chloride and heated under nitrogen atmosphere to 50° C. In the course of 2h 130.0 g tin tetrachloride was added dropwise, the temperature was than raised within 60 min to 130° C. to 140° C. The GC sample showed complete conversion into DBTC and MBTC. Then a stream of thoroughly dried hydrogen chloride was inserted with approximately 6 l/h while maintaining the temperature of the mixture. Effluent gas was neutralized and alkanes trapped in a cold trap. After 6 h the conversion was completed as seen in a GC measurement (EtMgBr MBTC 99.5%). The resulting mixture was distilled at 7 mbar to yield 264 g colorless MBTC b.p. 88° C. and 34 g dark residue (tin 23.8%; aluminium 8.47%; chloride 24.8%).

[0059] Preparation of Monobutyltintrichloride from Tetrabutyltin

[0060] In a round bottomed flask 120 g Tetrabutyltin technical grade (GC derivative EtMgBr showed TBT 73.31% and TBTC 25.32%) was mixed with 8.3 g anhydrous Aluminium chloride and heated under nitrogen atmosphere to 50° C. In the course of 2h 156.3 g tin tetrachloride was added dropwise, the temperature was than raised within 60 min to 130° C. to 140° C. The GC sample showed complete conversion into DBTC and MBTC. Then a stream of thoroughly dried hydrogen chloride was inserted with approximately 6 l/h while maintaining the temperature of the mixture. Effluent gas was neutralized and alkanes trapped in a cold trap. After 6 h the conversion was completed as seen in a GC measurement (EtMgBr MBTC 99.5%). The resulting mixture was distilled at 7 mbar to yield 248 g colorless MBTC b.p. 88° C. and 27.9 g dark residue (tin 23.8%; aluminium 8.47%; chloride 24.8%).

[0061] Likewise, the method may be used to prepare Monomethyltintrichloride from Dimethyltindichloride or Monooctyltintrichloride from Dioctyltindichloride.