WO2007006783A1 - Process for the preparation of monoalkyltin trihalides and dialkyltin dihalides - Google Patents

Abstract

The present invention relates to a process for the production of monoalkyltin trihalides of the formula RSnHal3, in which R = alkyl or cycloalkyl and Hal = Cl. Br or l. Said process comprises contacting the corresponding alkene or cycioalkene, stannous halide SnHal2, hydrogen halide HHal and optionally Sn metal, in the presence of at least one transition metal-based catalyst, thereafter isolating the monoalkyltin trihalides from the medium. The present invention also relates to a process for the production of dialkyltin dihalides of the formula R2SnHal2 from monoalkyltin trihalides of the formula RsnHal3,. in which R = alkyl or cycloalkyl and Hal = Cl, Br or l. Said process comprises contacting monoalkyltin trihalides RsnHal3 and Sn metal, optionally thereafter isolating the dialkyltin dihalides R2SnHal2 from the medium.

Description

PROCESS FOR THE PREPARATION OF MONOAKYL TIN TRIHALIDES AND DIALYL TIN DIHALIDES

[Field of the invention] 5

Monoalkyltin trihalides, by way of example, monoalkyltin trichlorides RSnCI₃ (R being C_nH_2n., ₁), particularly methyl-, butyl- and octyltin trichloride, are industrially important as intermediates for PVC stabilisers, glass coating chemicals and catalysts. A new route to produce monoalkyltin trihalides with n ≥

10 2 has been discovered. The method utilizes the corresponding alkene, tin dihalide and hydrogen haiide as raw materials and a transition metal complex as the catalyst. The reaction proceeds smoothly and selectively under mild conditions. The monoalkyltin trihalides either isolated from the reaction medium either coming from another source are reacted with tin metal to get a mixture of

15 tin dihalide and dialkyltin dihalides.

[The prior art and the technical problem]

Monoalkyltin trichlorides and dialkyltin dichlorides are currently prepared

20 through multistep processes. In these processes, the monoalkyltin trichlorides and dialkyltin dichlorides are formed as a mixture by disproportionation of the corresponding tetraalkyltin compound R₄Sn with SnCI₄. The tetraalkyltin compound is prepared by reacting trialkylaluminium or alkyl-Grignard reagents with SnCI₄. This route suffers from rather high raw material costs. Moreover, the

25 product composition depends on the length of the alkyl chain and reaction conditions, and is therefore hardly adjustable to the actual demand.

Fractionation by distillation may be required but becomes practically impossible for higher alkylchains (n = 8 or longer). Therefore, alternative methods for the selective production of monoalkyltin trichlorides and dialkyltin dichlorides are

30 highly desirable.

Alternative methods to prepare dialkyltin dichlorides include the selective diaikylation of tin tetrahalide using alkylaluminium reagents (see GB Pat 923179, DE 1 157617), or reaction of organic chloride with metallic tin. The latter reaction usually requires a catalyst, for example magnesium copper (see US 3,085,102) or hexamethylphosphoric triamide (HMPT, see US 4,049,689, 4,044,035) The low yields for higher alkyl chlorides and large amounts of catalyst needed make these methods generally unattractive from a commercial point of view

It is known that the reaction of SnCU with trialkylaluminum etherate R₃AI(GFT₂) / amide R₃AI(NFf₃) compounds or alcoholates R₂AI(OR^') allows the formation of RSnCI₃ Similarly, mixtures of monoalkyltin trichlorides and dialkyltm dichoπdes have been prepared in one step from SnCU using R₃Al and an excess of ether This is described in the following patents US 3,894,066, US 3,994,944, and patent application US 2004/0133022A1 Drawback of these procedures is the excess of alkylaluminiums often required to achieve good yields EP 1 225 177 describes a process for the production of monoalkyltin tnhalides of the formula RSnX₃, wherein R = alkyl or cycloalkyl and X = Cl, Br or I, involving a redistribution reaction between tetraorganotins triorganotin halides or diorganotin halides and tin tetrahalides, said process comprising contacting tetra- (R₄Sn) tri- (R₃SnX) or diorganotin halides (R ₂SnX₂) with SnX₄ to afford said monoorganotin tnhalides in the presence of at least one transition metal complex, said complex comprising at least one transition metal, M, selected from Group VIIl of the periodic Table of elements, at least one monodentate hgand or bidentate ligand, L, U or L' , and optionally one or more anions, X, of an organic or inorganic acid, as a catalyst or catalyst precursor This reaction still requires the production of the initial tetraorganotins triorganotin halides or diorganotin halides from tin tetrahalide and suffers from the formation of tin dihalide as byproduct

An alternative route to monoalkyltin trichlorides is the reaction of the corresponding alkylhalide with SnCb using a catalyst Useful catalysts are phosphonium halides, amines or phosphines, disulfides Se(II) or metal salts of group 1 -3, (e g LiCI or MgCl₂), or Mg metal with I₂ These reactions generally lequire high temperatures This is described in the following patents US 3,519,667, US 3,340,283, CA 1069129. GB 1 ,146.435. US 4,046,791 . Trialkylantimony compounds were found to be effective as catalysts in the case of alkyltin tribromides, but the lack of reactivity for the alkyltin trichlorides and the toxicity of the trialkylantimony catalysts renders this route less useful (E. J. Bulten, J. Organomet. Chem. 1975. 97, 167).

Reaction of α-olefins with stannane SnH₄ has been reported using a free radical catalyst (e.g. alkyl peroxides and cobalt naphthenate). The cryogenic conditions and low yields make this procedure unattractive from an industrial point of view. It has been described in GB 1 ,255,859. Addition of unactivated alkenes to HSnX₃ yielding RSnX₃ has been described to occur through a similar mechanism, but these produce the secondary substituted monoalkytin trihaiides in poor yields. It has been described in US 3,607,893. Hydrostannylations are known to occur when trialkyltin hydrides are reacted with substrates containing multiple bonds under radical conditions. Examples also exist where complexes of rhodium and palladium are successfully applied to catalyse the addition of trialkyltin hydrides to alkynes and alkenes to give mixed tetraorganotin compounds (M. Lautens, W. Klute, Angew. Chem. Int. Ed. Engl. 1996, 35, 442 and references therein).

The preparation of organotin compounds directly from SnCl₂ (or, alternatively, Sn metal), HCI and the corresponding alkene represents an attractive alternative route to monoalkyltin trichlorides. Its main advantages stem from the low raw material costs and ability to produce the desired alkyltin chloride selectively in one step. This reaction has been reported before for α,β- unsaturated carbonyl-containing substrates where it occurs without a catalyst under mild conditions. The carbonyl functionality acts as an activating group for the conversion in these substrates. Both monoorganotin trihaiides and diorganotin dihalides or mixtures thereof have been produced. It has been described in US 4,105,684, EP 0.01 1 ,280, US 4,080,362, US 4,130,573, J. W.

Burley. P. Hope, R. E. Hutton, C. J. Groenenboom, J, Organomet. Chem. 1979. 170, 21 , US Pat 4,202,830, J. W. Burley, P. Hope, A. G. Mack. J. Organomet.

Chem. 1984, However, unactivated alkenes are not reactive under these conditions. Reaction of 1-octene with HSnCI₃(Et₂O)₂ reportedly only results in trace amounts (< 1 %) of sec-octyltin trichloride (277, 37, R. E. Hutton, J. W. Burley, J. Organomet. Chem. 1978, 156. 369). n-Octyltin trichloride was formed in up to 81 % yield when [(^-C₅Hs)₂Zr(H)CI] and a stoichiometric amount of 1 - octene were reacted with 0.5 equivalent of SnCI₄ at room temperature. Obviously, the need for large amounts of zirconium reagent makes this route industrially less attractive (V. G. Kumar Das, O. Ghee Chee, J. Organomet Chem. 1987, 327 , 335).

A novel process for the direct and selective preparation of monoalkyltin trihalides from the corresponding unactivated alkene (e.g. 1 -octene), stannous halide (e.g. SnCI₂) and hydrogen haiide (e.g. HCI) in one single reaction step in the presence of a transition metal complex as a catalyst has been found. The reaction proceeds selectively, the only significant side product being isomerised alkene. Dialkyltin dihalides are then produced from monoalkyltin trihalides.

[Brief description of the invention]

The present invention comprises a process for the production of monoalkyltin trihalides of the formula RSnHal3, in which R = alkyl or cycloalkyl and Hal = Cl. Br or I, said process comprising contacting alkene, stannous halide and hydrogen halide in the presence of at least one transition metal complex as a catalyst or catalyst precursor; optionally thereafter isolating the monoalkyltin trihalides from the medium. In a preferred embodiment of the invention said complex comprises at least one transition metal M, at least one monodentate ligand or bidentate ligand, L or L', and optionally one or more anions. X, being defined as (i) the conjugate base of an organic or inorganic acid, (ii) a hydride or (iii) a hydrocarbyl fragment. In another preferred embodiment of the invention said complex is a transition metal salt consisting of transition metal M, and optionally one or more anions, X. being defined as the conjugate base of an organic or inorganic acid, and optionally one or more alkalimetal cations. Advantageously M is selected from Group VlII of the periodic Table of elements The reaction can be carried out with or without a solvent

The reaction proceeds selectively the only significant side product being alkene isomers resulting from isomeπsation of the starwig a'kene The alkene is currently applied m excess to the otner reactants The hydrogen halide ac d may be employed as gas or in solution The reaction proceeds smoothly at room temperature or above A multitude of organic solvents can be used, in particular, solvents like alcohols, ethers and apolar aromatic and aliphatic solvents and mixtures thereof Small amounts of water do not disturb the reaction

The invention also comprises a process to make dia'kyfttn dthafides The monoalkyltin trihalides (t) either isolated from the above reaction medium (it) either coming from another source are reacted with tin metal to get a mixture of tin dihalide and dialkyltin dihalides Optionally in option (ι) the tin metal can be added during the reaction to monoalkylttn tnhalide In that way the tin dihalsde formed can De consumed to produce monoalkyltin tπhalide

The invention also relates to the use of these monoalkyltin trihalides dialkyitin dihaiides and mixtures thereof made according to the process hereabove as intermediates for PVC stabilisers, glass coating chemicals and catalysts The invention aiso relates to the PVC stabilisers, glass coating Chemicals and catalysts having been made from the monoalkyltin tnhaltdes and dialkyltin dihalides made by the process of the present '"vertion

[Detailed description of the invention]

The present invention relates to a process for the production of monoalkyltin tπhalides of the formula RSnHaI₃, in which R = alkyl or cyctoalkyl and Hal = Cl Br or I Said process comprises contacting the corresponding alkene o^r cycϊøatkβne, stannous ralide SnHaI₂ hydrogen halide HHaI and optionally Sn metal, in the presence of at least one transition metal-based catalyst, thereafter isolating the monoalkyltin trihalides from the medium Advantageously, R is an alkyt linear or branched, in the range C2-C20 and preferably selected among C2. C3. C4. C5, C6, C7 and C8.

As regards the monoalkyltin trihalides, in a specific embodiment Hal is chloride. This means that the stannous rsaiide is SnCI₂ and hydrogen halϊde is

HCI. In the formula RSnHaIs the group R is preferably defined as an alky!

(linear or branched) or cycloalkyl having from 2 to 20 carbon atoms. Preferably π-butyl. butyl, n-heκyl, hexyl, n-octyl and octyl are used.

As regards the aikene (sometimes called olefin), it can be described, by way of example, as the following formula :

Rv

and the reaction route as follows (eq l ) :

SnI !al.,

R ₁ - SnI IaI₂ - HHa^*. ^K i

(eq. 1 ) in which R-] is H or is defined as an alkyl (iinear or branched or substituted), having from 1 to 18 carbon atoms. The aikene, but also cycioafkene. has advantageously from 2 to 20 carbon atoms. In a specific embodiment the aikene also can be described as R₁ (R₂)C=C(Rs) (R4) ^w'th R1 -R4 being any alkyl group (branched or linear or substituted) or hydrogen, R-| _ F^. R3 and/or R4 being optionally linked to any of the other R groups, for example Rf or R2 being linked to R3 or R^ or R1 being linked to R2. and the number of carbon atoms in R-j -R4 ranging from 0 to 18.

The olefin can contain functions and/or substituents. Advantageously this hydrocarbon has 4 to 8 carbon atoms. Especially 1 -butene and 1 -octene are relevant to produce industrially important organotins. As regards stannous halide, it can be SnHal2 or any precursor. Mention may be made, by way of examples, of Sn / SnHal4 blends and HHaI / Sn. The precursor also relates to SnHal2 / Sn / SnHal4 blends. The stannous halide is preferably anhydrous but also their aqua complexes can be used. The stannous halide SnHal2 can be produced in situ. According to a specific embodiment, SnHal2 can be partly or totally replaced by a Sn / SnHal4 blend (1/1 ratio) producing SnHa^ in situ.

As regards the hydrogen halide, it can be the hydrogen halide itself as gas or solution in a solvent or any precursor or any blend thereof. The precursor can be [HN(alkyl)3]Hal, another ammonium salt or other Lewis base adduct of hydrogen halide. When used as gas the hydrogen halide may be diluted with another gas. In a preferred embodiment of the invention the hydrogen halide can be HCI or [HN(CaH₅)_S]CI. In another preferred embodiment, Hal is chloride, the stannous haiide is SnCl₂ and hydrogen halide is HCI.

As regards the cataiyst, in its broadest form the catalyst is a transition metal-based catalyst.

According to a first embodiment of the invention, said transition metal- based catalyst can be a complex, said complex comprising at least one transition metal M₁ at least one monodentate ligand L or bidentate ligand L", and optionally one or more anions X, X being defined as (i) the conjugate base of an organic or inorganic acid, (ii) a hydride or (iii) a hydrocarbyl fragment.

Advantageously, the catalyst is a complex having the formula L¹MX₂ (I) wherein L' is a bidentate ligand, or

L₂MX₂ (II) or

[LMX₂J₂ (III) or L₄M (IV) wherein L is a monodentate ligand.

Preferably, the complex is M(PPh₃)₄.

According to a second embodiment of the invention, the transition metal- based catalyst can be a transition metal salt consisting of transition metal M, and optionally one or more anions. X, being defined as the conjugate base of an organic or inorganic acid, and optionally one or more alkalimetal cations.

More preferably, the transition metal-based catalyst can be a salt, said salt consisting of transition metal M. one or more anions X. X being defined as the conjugate base of an organic or inorganic acid, and optionally one or more alkalimetal cations M', such as Li^", Na^* or K". and/or one or more protons.

Advantageously, the salt is chosen from the group consisting of MX₂. IVT₂MX₄ and H₂MX₄. For example, M(HaI)₂ or K₂MX₄ can be employed.

According to a third embodiment of the invention, the transition metal- based catalyst can be a supported transition metal M in its zero valent oxidation state.

Preferably, said support is carbon.

Regardless of the type of the transition metal-based catalyst used within the framework of the present invention, i.e. a complex, a salt or a supported transition metal M. the transition metal M to be used is advantageously a Group VIII metal (also called columns 8-10), and preferred metals are Pt₁ Pd and/or Ni. The groups X may be anions of organic and/or inorganic nature, hydrogen or a hydrocarbyl fragment. In the catalyst species containing two X's (by way of example like L₂M(R)CI) the two X^'s can be mutually different. It is preferred to use Cl, Br, I, acetate, triflate, tosylate, hydride or alkyl. In a preferred embodiment of the invention L in formula (II) or (III) is selected from phosphine. alkene, amine, pyridine, organic sulfide, nitrile and imidazoline^- ylidene. L¹ is selected from phosphine containing ligand with aditionnal O or N, diphosphine, dialkene, diamine and bis(ϊmidazolϊne-2-ylϊdene) ligands. More in particular L is triphenylphosphine or L¹ = N, N. N', N'- tetramethytethylenediamine (TMEDA), or bypridine (optionally substituted), M is Pd or Pt and for catalyst (I), X is Cl. In a specific embodiment catalysts are choosen among Pd(PPh₃)₄ and Pt(PPh₃)₄.

As regards the solvent in general organic, aprotic or even protϊc solvents are preferred, especially aromatic solvents, chloroaromatic solvents, alkanes, ethers and alcohols. In particular tetrahydrofuran (THF), ethanol and 1 ,2-dimethoxyethane (DME) were found to be appropriate solvents.

As regards the operating conditions and the proportions, the reaction is made continuously or in batch. The batch process is preferred.

Temperature can be, by way of example, from ambient to 2Q0^cC. A range from

20 to 130^cC is advantageous, As regards the pressure, no pressure is necessary except to maintain the alkene, when it has a low boiling point, and hydrogen halide in the reaction medium. However, to speed up the reaction higher pressures may be advantageous. Preferred reaction times range from a few seconds to 48 hours. The molar ratio of olefin to SnHal2 falls within the range 0.1,- 1 to 200/1 , more advantageously 1/1 to 100-1 . The molar ratio of HHai to SnHai2 falls within the range 0.01/1 to 100/1 . The cataiyst loading (molar percentage of M) based on the number of moles of SnHal2 can be 0.001 to 5 %, more preferred 0.1 to 1.5%. Should a solvent be used, any proportion is convenient. The reaction is carried out in any usual apparatus. The reaction can be checked by taking samples and conventional analysis. The monoatkyltin trihalides can be separated from the reaction medium by any means such as. by way of examples, distillation, solvent extraction, crystallisation. About the yield based on olefin: a1 is the number of moles of olefin originally present at the beginning of the reaction, a2 is the number of moles of olefin converted. a3 is the number of moles of olefin converted to moπoalkyltin trihalϊde. the yield based on olefin is defined as the ratio a3/ai and typically is in the range 1 -80%. The selectivity based on olefin is defined as a3/a2 and is typically in the range 10-80%. About the Sn yield : b1 is the number of moles of Sn (present as Sn₁ SnHal2 or SnHaW) at the beginning of the reaction, b2 is the total number of moles of Sn (present as Sn, SnHal2 and SnHaI₄ ) converted, b3 is the number of moles of monoalkyltin trihalide produced.

The Sn selectivity is defined as the ratio b3/b2 and is in the range 95-100%.

The Sn yield is defined as b3/b1 . The conversion is defined as b2/b1 .

Also ratios Sn / SnHa^ > 1 can be used. Optionally Sn can be added to the reaction mixture in the course of reaction. In this case the excess Sn metal gives rise to dialkyltin dihalide and SnHaI₂ according to the following overall reaction stoichiometry;

(eq.2)

In eq 2 the alkene is only an example, it is clear that eq 2 concerns any alkene as described above.

2RSnHaIa +Sn → F^SnHa^ + 2SnHaJ2 (eq. 3)

The SnHaI₂ is entering the reaction of eq. 1 affording another equivalent of

RSnHaI₃.

As regards the conversion, yields and selectivities : a4 is the amount of olefin in moles converted to dialkyltin dihalide, b4 is the number of moles of dialkylfin dihalide produced. The conversion, yields and selectivities are now defined as follows : The olefin yield is defined as (a3+a4)/a1 . The olefin selectivity is defined as (a3+a4)/a2

The Sn yield is defined as (b3÷b4}/b1 . The conversion is defined as above.

The Sn selectivity is defined as the ratio (b3+b4)/b2.

Finally the two reactions of eq 1 and eq 3 can also be carried out as two consecutive reactions. In this case the monoalkyltin trihalide RSnHaI₃ is first produced. The next step is then performed by adding Sn metal to the reaction mixture. The stannous halide that is left after isolation of the RSnHaI₃ and R₂SnHaI₂ products can be recycled to the first step. By chosing the Sn/RSnHal₃ stoichiometry any R₂SnHaI₂ZRSnHaI₃ ratio in the product mixture can be chosen.

The present invention also relates to a process for the production of dialkyltin dihalides of the formula R₂SnHaI₂ from monoalkyltin trihalides of the formula RSnHaI₃, in which R = alkyl or cycloalkyl and Hal = Cl, Br or I, said process comprising contacting monoalkyltin trihalides RSnHaI₃ and Sn metal. optionally thereafter isolating the dialkyltin dihaiides R₂SnHaI₂ from the medium.

Advantageously, R is an alkyl, linear or branched, in the range C1 -C20 and preferably selected among C2, C3, C4, C5, C6, C7 and C8.

In a preferred embodiment, the monoalkyltin trihalides RSnHaL are produced by the process above-described

As regards the process to make dialkyltin dihalides from tin and monoalkyltin trihalides, the monoalkyltin trihalides (i) either isolated from the above reaction medium (ii) either coming from another source are reacted with tin metal to get a mixture of tin dihalide and dialkyltin dihalides, according to the following reaction;

2RSnHaI₃ +Sn → R₂SnHaI₂ + 2SnHaI₂ (_eq. ₃)

The reaction proceeds typically in the temperature range of 20 to 150⁰C with or without a catalyst and can be run with or without solvent. If solvent is applied, preferred solvents are organic apolar aliphatic or aromatic solvents or protic solvents or mixtures thereof. Water has a beneficiary effect on the reaction. Advantageously, the SnCI₂ formed may be isolated and recycled, for example by extraction with water followed by drying, and applied as the starting material for the monoaikyltin trihaiides production process as described above.

By choosing the Sn/RSnHal₃ stoichiometry, any R₂SnHaI₂ZRSnHaI₃ ratio in the product mixture can be chosen. In other words, by simply adjusting the amount of Sn, different mixtures of monoaikyltin trihaiides and dialkyltin dihalides can be prepared.

Particularly, if an amount of Sn metal is added in deficiency, a partial conversion of the monoaikyltin trihaiides RSnHaI₃ occurs and a mixture that contains both monoaikyltin trihaiides and dialkyltin dihalides is consequently obtained, in practice, such a "ready-to-go" mixture is currently used for making stabilizers.

Of course, the process of the present invention may further comprise a step of isolating the dialkyltin dihalides R₂SnHaI₂ from the medium, in particular from the monoaikyltin trihaiides and dialkyltin dihaϋdes mixture.

[Examples]

Example 1

A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 62 mg of Pt(O) (PPh₃)₄ and 138 mg of HNEt₃CI (1 .0 mmol). This mixture was then suspended by adding 0.5 ml_ of THF, followed by 1 .0 ml_ of 1 -octene and 0.5 ml_ of a 0.4 M solution of anhydrous SnCI₂ in THF (0.20 mmol). The vessel was placed in an oil bath and heated to 80⁰C and stirred for 16 hours.

After cooling down to room temperature, the liquid phase was ethylated with excess EtMgCI, and analysed by GLC using an internal standard. The yield is 10.5 mg (0.031 mmol ; b3/b1 = 16% ) of monooctyltin trichloride ^

Example 2

A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 5.0 mg of Pd(PPh₃J₄. Next. 1.0 ml_ of a 0.8 M solution of anhydrous SnCl₂ in THF (0.80 mmol) was added, followed by 2.0 mL of 1 -octene (12.5 mmol). The vessel was placed in an oil bath and heated to 60⁰C. Subsequently, 1 .5 mL of a 0.25 M HCI solution in THF (0.375 mmol) was slowly added and the resulting pale yellow solution was stirred for 1 hr. at 6O⁰C. After the reaction, the solvent and excess 1 -octene were removed in vacuo to yield an orange/red residu. This residu was suspended in 3.0 mL of toluene and the resulting suspension stirred vigorously for several minutes. The liquid phase was analysed by GLC after ethylation with excess EtMgCI. The yield is 1 12 mg (0.33 mmol ; b3/b1 = 41 %) of monooctyltin trichloride.

Example 3 A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 9.5 mg of Pd(PPh₃J₄ and 172 mg SnCI₂ (0.91 mmol). Next, 4 mL of THF were added. The vessel was placed in an oil bath and heated to 50⁰C, while propylene was bubbled through the solution. Subsequently, 4.0 mL of a 0.20 M HCI solution in THF (0.80 mmol) was slowly added and the resulting pale yellow solution was stirred for 1 .5 hr. at 50⁰C with propylene bubbling through the solution.

After the reaction, propylene bubbling was stopped and the solvent was removed in vacuo to yield an orange/red residue. This residu was suspended in 3.0 mL of toluene and the resulting suspension stirred vigorously for several minutes. The liquid phase was analysed by GLC, using an internal standard, after ethylation with excess EtMgCI. The yield is 12.6 mg (0.047 mmol ; b3/b1 = 6 %) of monopropyltin trichloride.

Example 4 In a pressure vessel equipped with an inlet to enable dinitrogen purge and a stirring bar, 15.0 mg of Pd(PPh₃)₄ was weighed in. The tube was brought under inert atmosphere and subsequently cooled to -10 ⁰C. Next, 4 mL of liquid 1 - butene was added, followed by 1 .0 mL of a 0.8 IVi SnCl₂ solution in THF and dropwise addition of 3.0 mL of a 0.25 M HCI solution in THF. The vessel was then sealed and the cooling bath removed. When the vessel had reached room temperature, the vent was opened for a few seconds to remove the excess pressure that had built up. The mixture was subsequently stirred at room temperature for 64 hrs.

After the reaction, the slightly turbid yellow reaction mixture was transferred to a second flask. The resulting residue was worked-up, ethylated and analysed by GLC as described for Example 2. The analysis showed the formation of 45 mg of butyitin trichloride (0.16 mmoi: b3/b1 = 20%).

Example 5

A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 15.0 mg of Pd{PPh₃)₄ and 38 mg SnCb- THF (1 mL) was added, followed by the addition of 3.0 mL of cyctoheκerte. Finally, 0.8 mL of a 0.20 M solution of HCI in THf was added dropwise by means of a syringe. After the addition was completed, the resulting mixture was heated to

60⁰C and stirred for 24 hr. at this temperature.

After cooling down to room temperature, the volatiies were evaporated under reduced pressure. The resulting residue was worked-up, ethylated and analysed by GLC as described for Example 2. The reaction yield was determined to be 4.0 mg (0.013 mmol; b3/b1 = 5°o) of monocyclohexyltin trichloride.

Exarτiβie_6

A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 1 mL of a THF solution containing 4.5 mg of Pd(PPh₃J₄ and 75.1 mg SnCI₂ (0.40 mmol). The reaction vessel was heated to 50⁰C. after which 1 .5 mL of styrene (13.1 mmol) was added. Subsequently. 2.0 mL of a 0.20 M HC! solution in THF (0.40 mmol) was slowly added and the resulting pale yellow solution was stirred for 16 hr. at 50⁰C. After the reaction, the solvent and excess alkene were removed in vacuo to yield an orange/red residu. This residu was suspended in 3.0 ml_ of toluene and the resulting suspension stirred vigorously for several minutes. The liquid phase was analysed by GLC, using an internal standard, after ethylation with excess EtMgCI. The yield is 5.9 mg (0.018 mmol: b3/b1 = 5 %) of mono(phenylethyl)tin trichloride.

Example 7

A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 1 .7 mg PdCI₂ and 634 mg SnCI₂. Ethanol (2 ml_) was added, followed by the addition of 4.4 ml of 1 -octene. The mixture was heated to 5O⁰C and 0.91 ml_ of a 2.75 M solution of HCI in ethanol were added by means of a syringe. After the addition was completed, the reaction mixture was stirred for 44 h at 50 ⁰C. After cooling down to room temperature, the volatiles were evaporated under reduced pressure. The resulting residue was worked-up, ethylated and analysed by GLC as described for Example 2. The reaction yield was determined to be 500 mg (1 ,48 mmol; b3/b1 = 44%) of monooctyltin trichloride.

ExarnoJeJ

A reaction vessel equipped with a magnetic stirring bar was charged with 10.8 mg Pd on activated carbon (10 % Pd) and brought under inert atmosphere. The catalyst was then suspended by adding 2.0 mL of acetone. The mixture was heated up to 50 ⁰C and 4.7 mL of 1 -octene were added. In a separate reaction vessel, a mixture of 671 mg SnCI₂, 0.66 mL of a 4 M solution of HCl in water (2.65 mmol) and 10.5 mL acetone was prepared, which was added by means of a syringe to the initial reaction mixture. The resulting mixture was stirred for 20 h at 50 ⁰C. After cooling down to room temperature, the volatiles were evaporated under reduced pressure. The resulting residue was treated as described for Example 2. A yield of 98 mg (0.29 mmol; b3/b1 = 8 %) of monooctyltin trichloride was calculated from the results of the GLC measurements. Example 9

A reaction vessel equipped with magnetic stirring was charged with 1 .00 g Sn powder (8.42 mmol) and inertised. Next, 5.0 ml_ of toluene was added, followed by 2.55 g of monobutyltin trichloride (9.04 mmol). This mixture was stirred at 105 ⁰C for 24 hrs.

After the reaction, the resulting light-grey suspension was cooled to room temperature and filtered. The remaining solids were extracted with 3 times 5 mL of toluene, and the combined organic fractions were evaporated to dryness. This resulted in 1 .31 g white crystalline material as the product. Identification by ¹H and ¹¹⁹Sn NMR, GLC (after ethylation with EtMgCI) and mp confirm the product to be > 98% pure dibutyltin dichloride (4.31 mmol).

Example 10 A reaction vessel equipped with magnetic stirring was charged with 485 mg of

Sn powder and brought under inert atmosphere. Next, 4.0 mL of toluene were added, followed by 1.41 g of octyltin trichloride. This mixture was stirred at

105 ⁰C for 24 hrs.

After the reaction, the resulting off-white suspension was cooled to room temperature and filtered. The remaining solids were extracted with toluene, and the combined organic fractions were evaporated to dryness. This resulted in

0.80 g (1 .92 mmol; (b3+b4)/b1 = 47%) of dioctyltin dichloride.

Example 1 1 A reaction vessel equipped with magnetic stirring was brought under inert atmosphere and charged with 15 mg of Pd(PPh₃)₄. Next. 238 mg of Sn powder was added, followed by 3 mL of THF and 5.0 mL of 1 -octene. The vessel was placed in an oil bath and heated to 50⁰C. Subsequently, 3 mL of a 0.3 M HCI solution in THF were added slowly and the resulting pale yellow solution was stirred for 40 hrs under gentle reflux.

The solvent and the excess of 1 -octene were removed in vacuo to yield an orange/red residue. This residue was suspended in 3.0 m L of toluene and the resulting suspension was stirred vigorously for several minutes The liquid phase was analysed by GLC after ethylation with excess EtMgCI The yield was 50 mg (0 12 mmol (b3τ-b4) fc>1 = 6 °o) of dioctyltin dichioride

The monαalkyitin tnhalides diaikyltin dihalides and mixtures thereof made according TO the processes hereabove described are currently used as intermediates for PVC stabilisers, glass coating chemicals and catalysts

Claims

1 . Process for the production of monoalkyltin trihalides of the formula RSnHaI₃, in which R = alkyl or cycloalkyl and Ha! = Cl, Br or I, said process comprising contacting the corresponding alkene or cycloalkene, stannous halide SnHaI₂, hydrogen halide HHai and optionally Sn metal, in the presence of at least one transition metal-based catalyst, thereafter isolating the monoalkyltin trihalides from the medium.

2. Process according to claim 1 wherein said at least one transition metal-based catalyst is a complex, said complex comprising at least one transition metal M, at least one monodentate ligand L or bidentate ligand L\ and optionally one or more anions X, X being defined as (i) the conjugate base of an organic or inorganic acid, (ii) a hydride or (iii) a hydrocarbyl fragment.

3. Process according to claim 2 wherein the complex is chosen from the group consisting of L₂MX₂, [LMX₂]?., L₄M and L¹MX₂.

4. Process according to claim 3 wherein the complex is M(PPlIs)₄.

5. Process according to claim 1 wherein said at least one transition metal-based catalyst is a salt, said salt consisting of transition metal M, one or more anions X, X being defined as the conjugate base of an organic or inorganic acid, and optionally one or more alkalimetal cations M', such as Li^*. Na' or K^", and/or one or more protons.

6. Process according to claim 5 wherein the salt is chosen from the group consisting of MX₂, M^MX₄ and H₂MX₄.

7. Process according to claim 6 wherein the salt is M(HaI)₂.

8. Process according to claim 1 wherein said at least one transition metal-based catalyst is a supported transition metal M in its zero valent oxidation state.

9. Process according to claim 8 wherein the support is carbon. _{} g}

10. Process according to anyone of claims 1 to 9 wherein the transition metal M is a Group VIII metal and is preferably selected among Pt, Pd and Ni.

11 . Process according to anyone of claims 1 to 10 wherein the stannous halide SnHa^ is produced in situ.

12. Process according to claim 1 1 wherein stannous halide SnHaI₂ is partly or totally replaced by a blend of Sn and SnHaI₄. preferably at a 1/1 ratio.

13. Process according to anyone of claims 1 to 12 wherein R is an alkyl, linear or branched, in the range C2-C20 and preferably selected among C2, C3, C4. C5, C6, C7 and C8.

14. Process according to anyone of claims 1 to 13 wherein the reaction is carried out in a solvent, preferably chosen among the organic, aprotsc or protic solvents.

15. Process according to claim 14 wherein the solvent is chosen among the aromatic solvents, ehloroaromatics, alkanes, ethers and alcohols and is, for example, tetrahydrofuran (THF), ethanoi or 1 ,2-dimethoxyethane (DME).

16. Process according to anyone of claims 1 to 15 wherein HaI is chloride, the stannous halide is SnCI₂ and hydrogen halide is HCI.

17. Process for the production of dialkyltin dihalides of the formula

R₂SnHaI₂ from monoalkyltin trihalides of the formula RSnHaI₃, in which R = alkyl or cycloalkyl and Hal = Cl, Br or I. said process comprising contacting monoalkyltin trihalides RSnHaI₃ and Sn metal, optionally thereafter isolating the dialkyltin dihalides R₂SnHaI₂ from the medium.

18. Process according to claim 17 wherein wherein R is an alkyl, linear or branched, in the range C1 -C20 and preferably selected among C2. C3. C4, C5, C6. C7 and C8. 19 Process according to claim 17 or 18 wherein said monoalkyltin trihalides RSnHaI₃ are produced by the process of anyone of claims 1 to 16.

20 Process according to any one of claims 17 to 19 wherein the amount of Sn metal is added in deficiency, said process further comprising an optional step of isolating the dialkyltin dihalides R SnHaL from the medium