Process for obtaining high-purity tricyclohexyl tin hydroxide on a high-yield basis

A process for producing tricyclohexyl tin derivatives, consists of a first phase in which Grignard reagent and tin tetrahalogenide are caused to react by feeding them into a reaction vessel in a molar ratio of 3:1, and a second phase in which after hydrolysis and anhydridization of the condensation mass, further Grignard reagent is added in an amount such as to maintain the total molar ratio, between the Grignard reagent and the tin tetrahalogenide, between 3.5:1 and 3.9:1.

BACKGROUND OF THE INVENTION 
The present invention relates to important improvements in the production 
of tricyclohexyl tin hydroxide from cyclohexyl magnesium halogenide and 
from tin tetrahalogenide. More particularly, the invention concerns a 
method which enables a very high-quality product to be obtained in almost 
the theoretically possible quantities, without requiring any purification 
process either on the intermediate products or on the finished products, 
and without isolating any intermediate phase. 
The process in accordance with the invention may be carried out either 
discontinuously or continuously. 
The continuous process offers particular advantages in industrial practice, 
the Applicants having carried out trials in their own works over a fairly 
lengthy period with excellent results. 
It is known from the literature on the subject that when Grignard reagent 
is caused to react with tin tetrahalogenide, so as to obtain tricyclohexyl 
tin halogenide the following reactions take place simultaneously: 
EQU 3C.sub.6 H.sub.11 MgX+SnX.sub.4 --(C.sub.6 H.sub.11).sub.3 SnX+3MgX.sub.2 ( 
1) 
(principal reaction) 
EQU 4C.sub.6 H.sub.11 MgX+SnX.sub.4 --(C.sub.6 H.sub.11).sub.4 Sn+4MgX.sub.2( 
2) 
(secondary reaction) 
EQU 2C.sub.6 H.sub.11 MgX+SnX.sub.4--(C.sub.6 H.sub.11).sub.2 SnX.sub.2 
+2MgX.sub.2 ( 3) 
(secondary reaction) 
wherein X=Cl, Br. 
It is also known that the importance of the secondary reactions (2) and (3) 
is associated with the type of technique used in the production process, 
and that the tetracyclohexyl tin and the dicyclohexyl tin dehalogenide 
that form during reactions (2) and (3) must be eliminated (if present) 
from the principal tricyclohexyl tin halogenide product so as not 
adversely to affect the quality of the final tricyclohexyl tin hydroxide 
product that it is required to obtain. 
In fact, when the products of the reactions (1), (2) and (3) are subjected 
to the subsequent reaction with caustic alkali, so as to obtain the final 
required product, the tetracyclohexyl tin remains unchanged, the 
dicyclohexyl tin dihalogenide is converted into dicyclohexyl tin oxide in 
the reaction: 
EQU (C.sub.6 H.sub.11).sub.2 SnX.sub.2 +MeOH--(C.sub.6 H.sub.11).sub.2 
SnO+2MeX+H.sub.2 O 
wherein X=Cl, Br Me=Na, K etc. and the tricyclohexyl tin halogenide is 
converted into the required tricyclohexyl tin hydroxide in the reaction: 
EQU (C.sub.6 H.sub.11).sub.3 SnX+MeOH--(C.sub.6 H.sub.11).sub.3 SnOH+MeX 
wherein X=Cl, Br Me=Na, K etc. 
Italian patent Nos. 967587 and 1002391 which describe techniques which are 
improved in respect of the previously known processes, have already 
provided the teaching which enables the formation of tetracyclohexyl tin 
to be avoided. However, it has not yet been possible to avoid the presence 
of dicyclohexyl tin dihalogenide in the final product resulting from the 
reaction between tin halogenide and Grignard reagent, by any technique yet 
described in the literature. Consequently, it has always been necessary 
hitherto to carry out purification in a phase following condensation 
involving the Grignard reagent and tin tetrahalogenide. Such purification 
consists either in the alcoholic crystallization of the tricyclohexyl tin 
halogenide or in the elimination by filtration of the dicyclohexyl tin 
oxide which forms during the reaction with caustic alkali. 
SUMMARY OF THE INVENTION 
The need for purification of the product in question is now eliminated by 
means of the present invention, which provides a procedure in which 
dicyclohexyl tin dihalogenide is converted into tricyclohexyl tin 
halogenide by reacting it, under suitable conditions, with Grignard 
reagent in accordance with the following reaction: 
EQU (C.sub.6 H.sub.11).sub.2 SnX.sub.2 +C.sub.6 H.sub.11 MgX--(C.sub.6 
H.sub.11).sub.3 SnX+MgX.sub.2 
wherein X=Cl, Br 
in the presence of previously formed tricyclohexyl tin halogenide, without 
the formation of tetracyclohexyl tin. 
More particularly, the present invention relates to a process whereby the 
Grignard reagent is added in two lots, namely 80-90% in a first 
condensation and 20-10% in a second condensation which follows the 
completion of the first condensation. 
As will be shown in further detail hereinafter, by adding the Grignard 
reagent in two separate lots, it becomes possible, in a surprising and 
advantageous manner, to overcome the condition--hitherto binding for any 
other technique in use--whereby, to carry out successful synthesis, the 
molar ratio between the Grignard reagent and tin tetrahalogenide should in 
no case exceed the value 3:1, if wishing to avoid the forming of 
substantial quantities of tetracyclohexyl tin. 
In the present invention such ratio can be exceeded (varying from 3.5:1 to 
3.9:1) without the formation of tetracyclohexyl tin, with the important 
consequence that the reaction can be completed by eliminating the 
dicyclohexyl tin dihalogenide which it has not been possible to cause to 
react in the known techniques. The success of this operation has resulted 
in a further very important advantage, namely the use of an entirely 
continuous process of synthesis and of production equipment for carrying 
out the process. 
To summarize, the present invention relates to a procedure for the 
production of tricyclohexyl tin derivatives, characterized essentially in 
that, in a first phase, Grignard reagent and tin tetrahalogenide are 
caused to react by feeding them into a reaction vessel in a molar ratio of 
3:1 and in that, in a second phase, after hydrolysis and anhydridization 
of the condensation mass, further Grignard reagent is added in an amount 
such as to obtain a total molar ratio between the Grignard reagent and the 
tin tetrahalogenide of between 3.5:1 and 3.9:1. 
The above-mentioned procedure can be carried out either as a continuous 
process or as a discontinuous process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the case where a continuous process is used, the invention provides that 
this comprises the following operations carried out in succession: 
preparation of the Grignard reagent (in accordance with the procedure 
described in Italian patent application No. 24100 A/75); 
condensation of the tin tetrahalogenide and the Grignard reagent, which 
condensation is carried out by adding the two reagents simultaneously in a 
reaction vessel and in a molar ratio of 3:1, Grignard to tin, throughout 
the reaction (and therefore under the conditions described in Italian 
patent No. 967587); 
hydrolysis of the condensation mass obtained, followed by separation of the 
organic phase; 
anhydridization and concentration of the organic phase containing the 
tricyclohexyl tin halogenide and the dicyclohexyl tin dihalogenide; 
condensation of the concentrated mass by means of a further amount of 
Grignard reagent; 
hydrolysis of the condensation mass followed by separation of the organic 
phase; 
reaction of the tricyclohexyl tin halogenide, contained in this organic 
phase, with caustic alkali; 
distillation, with steam, of the solvents; and 
filtration of the finished product. 
If however, the process is carried out on a discontinuous basis, the 
invention is achieved by separately preparing the Grignard reagent 
complexed with tetrahydrofurane and the complex of tin tetrahalogenide 
also with tetrahydrofurane (using, respectively, the procedures described 
in Italian patent application No. 24100 A/75 and Italian Pat. No. 
1002391), by then adding progressively the Grignard reagent complex to the 
tin tetrahalogenide complex to give a Grignard to tin molar ratio of 3:1, 
hydrolysing and anhydridizing the condensation mass obtained, and finally 
adding a further amount of Grignard reagent in such quantity that the 
total molar ratio of the latter to the tin tetrahalogenide is between 
3.5:1 and 3.9 to 1, so as to obtain tricyclohexyl tin oxide after 
hydrolysis, reaction with caustic alkali, distillation and filtration. 
The continuous process is particularly interesting and advantageous for the 
reasons detailed below. It is therefore important to describe in greater 
detail the operational features that characterize this process. 
When this method, in accordance with the present invention, is used on a 
practical basis, the Grignard reagent (obtained from the continuous 
production plant described in Italian patent application No. 24100 A/75) 
is first of all reacted with the tin tetrahalogenide in an inert solvent, 
preferably toluol, these materials being fed simultaneously into a 
reaction vessel in a stoichiometric molar ratio of 3:1 by means of 
metering pumps, the reaction temperature being kept at 
35.degree.-55.degree. C. and preferably 42.degree.-46.degree. C., while 
vigorously stirring the mixture. The compound issues from the overflow of 
the reaction vessel and passes into a second finishing, reaction vessel 
which is kept at a temperature of 60.degree.-75.degree. C., and preferably 
65.degree.-68.degree. C. The compound discharging from the overflow of 
this reaction vessel passes into a further reaction vessel where it is 
hydrolyzed, while at the same time an acid solution, preferably a 5% 
hydrochloric acid solution, is added by means of a metering pump. 
The compound issuing from the overflow is separated in a liquid-liquid 
separator, and the organic phase is fed into a distillation column, is 
anhydrized and concentrated to approximately 50% of its initial volume. 
The concentrated compound issuing from the distillation column is fed into 
a reaction vessel together with Grignard reagent by means of metering 
pumps, in such a way that the molar ratio of the Grignard reagent and the 
SnX.sub.4 ranges from 3.5-3.9:1, and is preferably 3.7:1. 
The temperature in the reaction vessel is maintained at 
35.degree.-50.degree. C., and preferably at 40.degree.-45.degree. C. 
The compound issuing from the overflow of the reaction vessel is passed 
into a further finishing reaction vessel which is maintained at a 
temperature of 40.degree.-60.degree. C. and preferably at 
45.degree.-50.degree. C. 
The compound issuing from the overflow of this reaction vessel passes into 
yet another reaction vessel where it is hydrolyzed, while at the same time 
an acid solution, preferably a 15% hydrochloric acid solution, is added by 
means of a metering pump. 
The compound issuing from the overflow is separated in a liquid-liquid 
separator, and the organic phase is passed through a porous diaphragm at 
the bottom of a column filled with Raschig rings and containing an aqueous 
caustic alkali, preferably 15% caustic soda. At the same time, a metering 
pump supplies the bottom of the column with aqueous caustic alkali, 
preferably 15% NaOH, so that the molar ratio 
EQU (C.sub.6 H.sub.11).sub.3 SnX:NaOH 100% 
is 1:1.5-2.5, and preferably 1:2. The temperature in the column is kept at 
60.degree.-75.degree. C., and preferably 68.degree.-70.degree. C. 
The organic phase, separated from the aqueous phase, that issues at the top 
of the column, is distilled so as to eliminate the solvents, and the 
tricyclohexyl tin hydroxide is separated by filtration and then dried. 
A product of 96-98% purity is obtained, with a yield of 95-96% calculated 
on the basis of the Sn tetrahalogenide. 
This continuous process results in considerable advantages, the main ones 
of which are: 
a very high production potential; for example with equipment of a volume of 
between 10 and 20 liters, 150-200 kg of finished product can be produced 
each day; 
almost complete elimination of the processing dangers connected with the 
production and use of Grignard reagent, in view of the small quantities of 
products present in the working line; 
a very high yield and the total absence of sideproducts derived from tin 
and difficult to dispose of or destroy, thus resulting in the well-known 
ecological problems; 
a high and constant quality in the finished product without the need for 
more or less complicated purification operations; 
stirring can be carried out easily and efficiently, and the heat of 
reaction can be readily dissipated in view of the small dimensions of the 
equipment. 
The following examples are provided for the purpose of illustrating the 
invention and of making it more comprehensible. However the invention is 
in no way limited to these examples. 
EXAMPLE 1 
This first example relates to a process of the continuous type in 
accordance with the invention, and the description thereof refers to the 
attached drawings consisting, as signified above, of three sequential 
sheets which illustrate the equipment for carrying out said process. 
A reaction vessel 1, equipped with stirring means 2, a thermometer, a 
gravity cooling system, an outer cooling jacket 3 and a lateral overflow 
discharge line 4, and having a useful capacity of 15 liters to the 
overflow while stirring, is charged with 
3 liters toluol; and 
1 liter tetrahydrofurane. 
simply for the purpose of starting the equipment, so as to facilitate 
stirring and not to start with an empty reaction vessel. Subsequently or 
in any case when the equipment is started, the following are 
simultaneously added by means of metering pumps 5 and 6: 
23.8 liters/hour of a solution of cyclohexyl magnesium chloride in 
tetrahydrofurane, emanating from an apparatus for continuously producing 
Grignard reagent, of the type described in Italian patent application No. 
24100 A/75, this material corresponding to 
7.63 kg/hour at 100%=0.053 kmol/hour: and 
35 liters/hour of a toluenic solution of tin tetrachloride corresponding to 
4.64 kg/hour of SnCl.sub.4 100%=0.0178 kmol/hour. 
Therefore the reagents are introduced in such a way that they react in the 
3:1 tin tetrachloride/Grignard reagent molar ratio, in accordance with the 
teachings of Italian Pat. No. 967587 in the name of the present assignee. 
Water is caused to circulate in the jacket 3 of the reaction vessel 1 at a 
temperature such that the vessel is maintained at a temperature of between 
42.degree. and 46.degree. C. 
Stirring should be carried out efficiently so as to facilitate 
heat-exchange and to avoid local overheating. 
When the reaction vessel is full, the reaction composition runs out through 
the lateral overflow 4 and falls into a second reaction vessel 7 similar 
to the vessel 1. The reaction is completed in this vessel 7 and a 
temperature of between 65.degree. and 68.degree. C. is reached. This 
temperature is kept constant in the reaction vessel by circulating hot 
water in the jacket 8 of the vessel 7. 
The compound that escapes through the lateral overflow 9 of the reaction 
vessel 7 falls into a hydrolyzing vessel 10 having the same dimensions as 
the previous ones, but made of acid-resisting material. Simultaneously 
with the composition issuing from the reaction vessel 7, 
14 liters of 5% hydrochloric acid per hour are fed to the reaction vessel 
10 by means of a metering pump 11. 
In the vessel 10, the temperature is maintained at 35.degree.-40.degree. C. 
by cooling with water in the jacket 12 of this vessel. 
The hydrolysis composition which is formed in the reaction vessel 10 and is 
made up of an organic phase containing tricyclohexyl tin chloride and 
dicyclohexyl tin dichloride and of an aqueous acid phase, containing 
magnesium chloride, passes through the lateral overflow 13 of the vessel 
10 and into the liquid-liquid separator 14 in which separation of the two 
phases takes place. 
The acid phase is eliminated by passing it into a tank 15, whereas the 
organic phase is fed to a distillation column 16 to be concentrated and 
anhydrized. 
The distilled solvents emerge from the top 16' of the column 16 and are 
passed on for collection, whereas from the bottom of the column a 
concentrated solution emerges at a rate of 30 liters per hour and is 
collected in a tank 17. 
Into a reaction vessel 18 (similar to the vessel 1 and located downstream 
of the column 16), by means of metering pumps 19 and 20 respectively, are 
simultaneously fed, 
30 liters/hour of the concentrated solution obtained in the tank 17; and 
5.6 liters/hour of cyclohexyl magnesium chloride in a solution of 
tetrahydrofurane, corresponding to 
1.792 kg/hour at 100%=0.0125 kmol/hour. 
The temperature in the reaction vessel is maintained at 
40.degree.-45.degree. C. by the circulation of water in the jacket 21 of 
the reaction vessel 18. 
The composition issues through a side overflow 22 of the reaction vessel 18 
and falls into a finishing reaction vessel 23 similar to the vessel 1. In 
the reaction vessel 23, the temperature is maintained at 
45.degree.-50.degree. C. by the circulation of hot water in the jacket 24 
of this vessel 23. 
From a lateral overflow 25 of the reaction vessel 23, the reaction 
composition falls into a further reaction vessel 26, which is similar to 
the vessel 12 and into which are simultaneously fed, through a metering 
pump 27: 
3.5 liters/hour of 15% hydrochloric acid. 
The hydrolyzed composition resulting therefrom consists of an organic phase 
containing tricyclohexyl tin chloride, and of an acid aqeuous phase 
containing magnesium chloride, and said composition issues from a side 
overflow 27 of the reaction vessel 26 and passes to the liquid-liquid 
separator 28 wherein the two phases are separated. 
The acid phase is eliminated by passing it to the tank 15, whereas the 
organic phase is passed through a porous diaphragm 29 into the bottom of a 
column 30, having a diameter of approximately 10 cm and a height of 
approximately 150 cm, filled with Raschig rings and containing 15% caustic 
soda up to the top outlet. 
8.15 liters/hour of 15% NaOH are further added through a feed 31 into the 
bottom of the column 30, simultaneously with the organic solution. 
The temperature in the column is maintained at 70.degree. C. by means of 
hot water circulating in the jacket. Also the added reagents are 
preheated. 
The top of the column 30 is designed to act as a liquid-liquid separator so 
that the organic tricyclohexyl tin hydroxide solution and the alkaline 
aqueous phase come out from the column simultaneously, but separately. The 
alkaline aqueous phase is then eliminated. 
The organic phase, collected in the tank 32, is passed by means of a 
metering pump 33 to a distillation apparatus consisting of a 
preconcentration column 34 and a distillator 35, where the residual 
solvents are eliminated by distillation with steam. 
The tricyclohexyl tin hydroxide is then filtered and dried. 
6.52 Kg/hour of tricyclohexyl tin hydroxide of 96.8% titre are obtained. 
The yield calculated on the basis of the tin tetrachloride is 95% of 
theory. 
EXAMPLE 2 
This second example relates to a discontinuous process in accordance with 
the invention. 
400 ml of anhydrous toluol, and 
80 g of tin tetrachloride=0.307 mol are fed into a reaction vessel provided 
with stirring means, a thermometer and gravity cooling means. 
60 ml of tetrahydrofurane=0.74 mol are fed into the solution obtained, at a 
temperature of between 0.degree. and 5.degree. C. 
The complex SnX.sub.4.2R'.sub.2 O (see Italian Pat. No. 1002391 in this 
connection) is obtained in the form of a white crystalline precipitate. 
While maintaining the temperature at 38.degree.-42.degree. C., 411 g of 
cyclohexyl magnesium chloride in tetrahydrofurane =131.5 g at 100%=0.921 
mol (prepared as described in Italian patent application No. 24100 A/75) 
are added to this composition over a period of approximately 30 minutes. 
The mixture is heated to 70.degree. C. and is maintained at that 
temperature for 30 minutes. 
After cooling, 200 ml of 5% HCl are added. 
The organic phase is separated from the aqueous phase. The organic phase is 
concentrated to approximately half its initial volume, by distillation. 
71 g of cyclohexyl magnesium chloride solution in tetrahydrofurane=22.7 g 
at 100%=0.159 mol are added to the concentrated solution over a period of 
about 30 minutes and at a temperature of between 40.degree. and 45.degree. 
C. 
The mixture is held at 40.degree.-45.degree. C. for 30 minutes. 
50 ml of 15% HCl are then added. 
The organic phase is then separated from the aqueous phase. 
82 g of 15% NaOH=0.614 mol are added to the organic phase. 
The mixture is heated to 70.degree. C. and is held at this temperature for 
1 hour. 
The organic phase is separated from the aqueous phase. 
The solvents are distilled with steam. 
The white crystalline product obtained is filtered, washed with water and 
dried. 
113 g of tricyclohexyl tin hydroxide are obtained. Yield: 95.6%. 
Titre of the product: 96%.