Boron tris-(dialkyl-dithiocarbamates) and a process for their preparation

Boron tris-(dialkyl-dithiocarbamate) of the general formula ##STR1## wherein R and R' represent the same or different branched- or straight-chain saturated or unsaturated alkyl radicals having from 1 to 16 carbon atoms and a process for preparing the same, comprising reacting 3 moles of an alkali dialkyl-dithiocarbamate of the general formula ##STR2## wherein R and R' are as defined in claim 1 and Me.sup.+ represents Na.sup.+, K.sup.+ or NH.sub.4.sup.+ with one mole boron tribromide, boron trichloride or boron trifluoride in an inert medium, separating the so-formed alkali metal or ammonium halide and isolating the boron dithiocarbamates are suitable as additives for hydraulic oils or permanent gear lubricant oils.

This application relates to novel boron dithiocarbamates. 
A large number of metal dithiocarbamates has been described, see Elsevier 
Monographs "The Dithiocarbamates and related Compounds" by Thorn and 
Ludwig (1962), Table I, pages 12 to 34. 
The present invention provides novel boron tri-(dialkyl-dithiocarbamates) 
of the general formula 
##STR3## 
wherein R and R' are the same or different branched- or straight-chain 
saturated or unsaturated hydrocarbon groups having from 1 to 16 carbon 
atoms. These hydrocarbon groups may also be cycloalkyl groups, such as 
cyclohexyl. 
Furthermore, the invention also provides novel processes for preparing the 
boron dithiocarbamates of the general formula I. The preparation of these 
compounds takes place according to the following equations: 
##STR4## 
In these equations, R and R' are as defined above, X represents bromine, 
chlorine or fluorine and Me is an alkali metal or ammonium ion, preferably 
the sodium ion. 
The preparation of the alkali dialkyl-dithiocarbamates is basically known. 
For preparing the sodium dialkyl-dithiocarbamates, one usually proceeds as 
follows: 
A 50% sodium hydroxide solution is poured into methanol. A secondary amine 
is added thereto and carbon disulfide is added drop by drop. All reaction 
components are used in stoichiometric amounts. Carbon disulfide may also 
be used in excess amounts. The mixture is mechanically stirred for 1 to 3 
hours. The formation of the sodium dithiocarbamate is then terminated. 
This solution can directly be used as starting material for the subsequent 
prepration of boron tris-(dialkyl-dithiocarbamates) and the reaction can 
be continued in the same reaction vessel if one subsequently adds thereto, 
dropwise, 1 mole of a solution of the boron trifluoride-diethyl ether or 
-methanol complex in diethyl ether per 3 moles of the sodium 
dithiocarbamate. 
Instead of methanol, also other solvents which are miscible with water can 
be used, for example, ethylene glycol monoalkyl ether, tetrahydrofuran, 
dioxane, ethanol, propanol or isopropanol. The boron trifluoride complex 
compounds are not as susceptible to hydrolysis as the free boron halides 
so that the process may be carried out in aqueous-alcoholic solution; 
however, the water content in the reaction medium should not exceed 15% by 
weight. 
The reaction is slightly exothermic in the two steps. Additional heating or 
external cooling is, therefore, usually not necessary. The reaction is 
conducted at 0 to 90, preferably at 20.degree. to 70.degree. C. 
After termination of the reaction with the boron trifluoride complex, the 
mixture is additionally stirred for some hours. It is then sucked off from 
the crystallized alkali metal fluoride. The mixture of water and solvent 
is distilled off from the filtrate. To avoid a temperature in excess of 
70.degree. C., residual amounts of solvents are suitably distilled off in 
vacuo. One obtains faintly yellow to amber colored oils which are 
preferably filtred again until they are clear. 
If one wants to use instead of the boron fluoride-diethylether or -methanol 
complex, boron tribromide, boron trichloride or boron trifluoride as 
reaction component, it is necessary to use the corresponding alkali 
alkyl-dithiocarbamate in an anhydrous condition. The aqueous solution 
formed at first must be reduced to dryness before the alkali 
alkyl-dithiocarbamate can be reacted in an anhydrous inert solvent with 
the boron halide. 
Suitable inert solvents for the reaction in the anhydrous medium are 
aliphatic or aromatic hydrocarbons or lower dialkyl ethers. As to the 
temperatures to be observed, the same applies here as in a 
water-containing medium. 
The so-called "one pot process" can be applied in both cases, i.e. the 
preparation of the boron tris-(dialkyl-dithiocarbamate) can take place in 
the same reaction vessel wherein in the first step the alkali or ammonium 
dialkyl-dithiocarbamate had been prepared from a suitable secondary amine, 
carbon disulfide and alkali hydroxide, or according to another process 
known per se. 
The new boron dithiocarbamates of the general formula I are suitable as 
additives for hydraulic oils or permanent gear lubricant oils. 
The preparation of the compounds of the present invention is illustrated by 
a few examples:

EXAMPLE 1 
Boron tris-(di-2-ethylhexyl-dithiocarbamate) 
15 kg of a 50% sodium hydroxide solution are poured into 94 liters methanol 
in a 200 liters glass apparatus with mechanical stirring. 45 kg 
Di-2-ethylhexyl amine are subsequently added thereto. 15 kg Carbon 
disulfide are then added, drop by drop, in the course of 30 minutes. The 
mixture is thereafter stirred for another 2 hours. A solution of 7.5 kg 
boron trifluoride-diethyl ether complex (a 50%-solution) in 19 liters 
ether is added thereto dropwise over a period of 90 minutes. The mixture 
is stirred for another 3 hours, closed and allowed to stay overnight. It 
is sucked off the next morning from precipitated sodium fluoride through 
an earthenware suction filter. The mixture of methanol, water and ether is 
distilled off from the filtrate, at the end in vacuo, whereby it is not 
heated above 70.degree. C. After cooling, the coil is again sucked off. 
46.6 kg Of a clear amber colored oil are obtained which has a purity of 
100.1%, based on the total amount of nitrogen. The yield was 77.62% of the 
calculated amount, based on BF.sub.3. 
EXAMPLE 2 
Boron tris-(di-2-ethylhexyl-dithiocarbamate) 
24 g of a 50% sodium hydroxide solution are poured into 250 ml water. 72.3 
g Di-2-ethylhexyl amine are added thereto. 20 ml carbon disulfide are 
added thereto dropwise over a period of 20 minutes with mechanical 
stirring. The mixture is stirred for another 30 minutes. It is then 
reduced to dryness in vacuo in a rotary evaporate at a bath temperature of 
50.degree. C. The dry powder is dissolved in 200 ml di-isopropylether, 
which was dried over molecular sieve. A solution of 25 g boron tribromide 
in 100 ml di-isopropyl ether, which was likewise dried over molecular 
sieve, is added thereto dropwise over a period of one hour with mechanical 
stirring. The mixture is stirred for another 3 hours and is allowed to 
stay overnight. It is sucked off from sodium bromide under weak partial 
vacuum. The di-isopropyl ether is distilled off. The residue is dried in 
vacuo at 70.degree. C. One obtains 44 g of a yellowish oil having a purity 
of 96.9%, based on nitrogen. 
EXAMPLE 3 
Boron tris-(di-2-ethylhexyl dithiocarbamate) 
40 g sodium hydroxide granules are dissolved in 350 ml methanol. 241 g 
di-2-ethylhexyl amine are added thereto. 64 ml Carbon disulfide are added 
thereto with mechanical stirring within 20 minutes. The mixture is further 
stirred for another 2 hours. Thereafter, 171 g boron trifluoride-methanol 
complex (14% BF.sub.3) are added thereto dropwise over a period of one 
hour. The mixture is further stirred for another 2 to 3 hours, closed and 
allowed to stay overnight. It is then sucked off from sodium fluoride. The 
solvent is distilled off and the residue is dried in vacuo. Finally, it is 
sucked off again. One obtains 223 g of a yellowish oil having a purity of 
97.3%, based on nitrogen. The yield was 69.7% of the calculated amount, 
based on BF.sub.3. 
EXAMPLE 4 
Boron tris-(diamyl-dithiocarbamate) 
150 g of a 50% sodium hydroxide solution are poured into 940 ml methanol. 
293 g diamyl amine are added thereto. Thereafter, 120 ml carbon disulfide 
are added dropwise with mechanical stirring over a period of 30 minutes. 
The mixture is further stirred for another 2 hours. 75 g Boron 
trifluoride-diethyl ether complex are poured into 190 ml ether. This 
solution is added dropwise within 50 minutes to the solution of the sodium 
dithiocarbamate. The mixture is further stirred for another 3 hours. It is 
then sucked off from sodium fluoride. The solvent mixture is distilled off 
from the filtrate. The residue is dried in vacuum in a water bath at 
70.degree. C. for one hour. It is thereafter sucked off again. One obtains 
325 g of a yellowish colored oil having a purity of 98.45%, based on 
nitrogen. The yield amounts of 83% of the calculated amount, based on 
boron trifluoride. 
EXAMPLE 5 
Boron tris-(ditridecyl-dithiocarbamate) 
80 g of a 50%-sodium hydroxide solution is poured into 500 ml methanol. 381 
g Ditridecyl amine are added thereto. Thereafter, 64 ml carbon disulfide 
are added dropwise at reflux with mechanical stirring within 30 minutes. 
The mixture is further stirred for another 2 hours. A solution of 45 ml 
boron trifluoride-ethyl ether complex is subsequently added thereto, drop 
by drop, within 1 hour. The mixture is further stirred for another 3 
hours. It is closed and allowed to stay overnight. It is then sucked off 
from sodium fluoride. The solvent mixture is distilled off from the 
filtrate. The residue is dried in vacuo in a rotary evaporator at a bath 
temperature of 70.degree. C. The so-formed oil is again sucked off after 
cooling. One obtains 393 g of an amber colored viscous oil having a 
content of 98.7%. The yield amounts to 85.4% of the calculated amount. 
It will be appreciated that the instant specification and claims are set 
forth by way of illustration and not limitation, and that various 
modifications and changes may be made without departing from the spirit 
and scope of the present invention.