Process for the purification of pentafluorophenyl boron compounds

One aspect of the invention is a process for purifying a pentafluorophenyl boron compound from a crude mixture comprised of the pentafluorophenyl boron compound and impurities, the impurities at least comprised of an ether and water, the process comprising: (a) mixing the crude mixture with an azeotropic organic solvent which (i) is capable of azeotrope formation with the water and (ii) has a boiling point above the boiling point of the ether; (b) distilling the resulting solution to remove at least a portion of the impurities; and (c) cooling the distilled solution so that a precipitate comprised of the pentafluorophenyl boron compound is formed. Processes are also described for producing pentafluorophenyl boron compounds which are particularly pure, dry and fine.

TECHNICAL FIELD 
This invention pertains to novel processes for the isolation, purification 
and drying of pentafluorophenyl boron compounds and to the production of 
solid forms of such compounds having low water content (e.g., no more than 
about 500 ppm) and small average particle size (e.g., no more than about 
200 microns). 
BACKGROUND 
Pentafluorophenyl boron compounds such as, e.g., bis-, tris- and 
tetra-kispentafluorophenyl boron derivatives are useful in forming olefin 
polymerization catalyst complexes with metallocenes. Processes for the 
production of such compounds have been disclosed, for example, in U.S. 
Pat. Nos. 5,488,169, 5,493,056, 5,510,536 and 5,545,759 to Ikeda et al., 
and 5,473,036 to Piotrowski, the disclosures of which are incorporated 
herein by reference. However, the known processes for isolating, purifying 
and drying these pentafluorophenyl boron compounds from crude reaction 
mixtures require large amounts of solvent, multiple reactors, long cycle 
times, and low temperatures of operation. Often such processes involve the 
use of aqueous solutions which introduce water impurities to the final 
product. The product is typically dried in vacuum to water levels of about 
2000 ppm. However, even very small amounts (e.g., 1000 ppm) of water can 
drastically diminish the activity of the catalyst complexes. In addition, 
so far as is known, previous methods of producing solid forms of such 
compounds have resulted in products having excessive average particle 
sizes, thus requiring grinding or other additional processing to obtain a 
more advantageous average particle size. 
A need therefore exists for a facile process for the isolation, 
purification and drying of crude wet mixtures comprised of 
pentafluorophenyl boron compounds. Additionally, a need exists for an 
efficient process for producing solid pentafluorophenyl boron compounds 
with an average particle size of no more than about 200 microns. 
DESCRIPTION OF THE INVENTION 
The present invention is deemed to satisfy these needs in a highly 
efficient way. In one embodiment, this invention provides a process for 
purifying a pentafluorophenyl boron compound from a crude mixture 
comprised of the pentafluorophenyl boron compound and impurities, the 
impurities at least being comprised of ether and water. The process 
comprises: 
a) mixing the crude mixture with an azeotropic organic solvent which (i) is 
capable of azeotrope formation with the water and (ii) has a boiling point 
above the boiling point of the ether; 
b) distilling the resulting solution to remove at least a portion of the 
impurities; and 
c) cooling the distilled solution so that a precipitate comprised of the 
pentafluorophenyl boron compound is formed. 
This process enables isolation and purification of the pentafluorophenyl 
boron compound from the crude mixture in a single pot reaction, if 
desired. The crude mixture and the azeotropic organic solvent are mixed 
together in no particular order, and in fact may be simultaneously fed 
into one another, if desired. The weight ratio of pentafluorophenyl boron 
compound to azeotropic organic solvent in the mixture may range from about 
1:1 to about 1:30, preferably from about 1:5 to about 1:15. The amount of 
azeotropic organic solvent used should be sufficient to permit 
chromophoric impurities in the crude mixture to dissolve into solution 
under the process conditions employed. 
The resulting solution may be distilled at temperatures typically in the 
range of about 20.degree. to about 150.degree. C., preferably about 
60.degree. to about 110.degree. C., and, if distilled under vacuum, more 
preferably about 22.degree. C. to about 25.degree. C. The distillation 
typically is conducted over a period of time sufficient to remove at least 
a portion of the impurities present in the crude mixture. Typically, 
distillation is conducted for a period of time in the range of about 1 to 
about 5 hours. 
After distillation, the distilled solution (i.e., the solution which 
remains after the distillate is removed) is cooled to a temperature in the 
range of about -20.degree. to about 120.degree. C., preferably in the 
range of about 0.degree. to about 60.degree. C., and most preferably in 
the range of about 22.degree. to about 25.degree. C. A precipitate forms 
during this step, and may be removed from the solution by any conventional 
method, but is preferably removed by filtration. In this and all other 
processes of this invention, the recovered precipitate has a water content 
of no more than about 1000 ppm, preferably no more than about 500 ppm, and 
more preferably no more than about 100 ppm. 
In another embodiment, the above-described process of this invention is 
modified so that an aliphatic hydrocarbon is mixed with the distilled 
solution while the solution is agitated. The aliphatic hydrocarbon may be 
mixed with the distilled solution while the solution is being cooled, or 
after the step of cooling has been completed. A precipitate which 
comprises the pentafluorophenyl boron compound is formed having an average 
particle size of no more than about 200 microns, more preferably no more 
than about 100 microns, and most preferably no more than about 25 microns. 
This process facilitates isolation, purification, drying, and particle 
size control in the same reaction vessel, if desired. 
When mixing the aliphatic hydrocarbon with the distilled solution, the 
aliphatic hydrocarbon is preferably slowly added to the distilled solution 
over a period of about 1 to about 30 minutes, and as noted above the 
distilled solution is agitated during addition of the aliphatic 
hydrocarbon. Sufficient agitation is applied so that the average particle 
size of the resulting precipitate is no more than about 200 microns, more 
preferably no more than about 100 microns, and most preferably no more 
than about 25 microns. For commercial applications, the agitation 
preferably is provided by use of an industrial blender such as, e.g., a 
3-speed, 4-liter, explosion-proof blender available from Waring, using a 
speed setting preferably in the range of about 15,500 to about 22,000 rpm 
for a period preferably of about 10 to about 60 minutes. The average 
particle size of the precipitate product resulting from this process will 
vary depending upon, and may be controlled by, the level of agitation 
applied to the solution. 
This invention also provides a process for the production of a 
pentafluorophenyl boron compound having a particle size of no more than 
about 200 microns from a solution formed from a crude form of the 
pentafluorophenyl boron compound (e.g., one having particle size of more 
than about 200 microns) and an organic solvent, the process comprising (i) 
mixing an aliphatic hydrocarbon with the solution under an inert 
atmosphere and agitating the solution at a temperature in the range of 
about -20.degree. to about 120.degree. C., and (ii) recovering at least a 
portion of the pentafluorophenyl boron compound from the solution as 
precipitate. The aliphatic hydrocarbon and the solution are mixed together 
in no particular order, and in fact may be simultaneously fed together, if 
desired. The precipitate formed may be recovered from solution in any 
conventional manner, but is typically recovered by filtration. The crude 
form of the fluorinated aromatic boron compound will typically at least 
have chromophoric impurities which cause the compound to exhibit a color 
other than white. Through this process, such colorful impurities are 
dissolved into the organic solvent, where they remain during precipitation 
and recovery of the pentafluorophenyl boron compound. The resulting 
product is white in color, highly pure, and has an average particle size 
of no more than about 200 microns, more preferably no more than about 100 
microns, and most preferably no more than about 25 microns. In a 
particularly preferred embodiment the pentafluorophenyl boron compound is 
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, the weight ratio 
of organic solvent to aliphatic hydrocarbon is about 7:3, the temperature 
in mixing step (i) is in the range of about 22.degree. to about 25.degree. 
C., and mixing step (i) is performed over a period of time in the range of 
about 10 to 15 minutes. Under these conditions, the product is 
exceptionally pure, dry and fine. 
The process conditions for all of the processes of this invention include 
use of substantially anhydrous, inert atmosphere such as dry nitrogen, 
argon, or the like. The processes of this invention are not particularly 
pressure dependent. The pressure used may be in the range of from about 
0.1 to about 1500 mm Hg and preferably about 1.0 to about 1000 mm Hg. The 
more preferred pressures are atmospheric or near-atmospheric (700-800 mm 
Hg) pressures. 
The pentafluorophenyl boron compound may include, for example, derivatives 
of bis(pentafluorophenyl)borane, tris(pentafluorophenyl)borane, or 
tetrakis(pentafluorophenyl)borate, including mixtures of any two or more 
of the foregoing. Non-limiting examples of such pentafluorophenyl boron 
compounds include N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, 
halomagnesium tetrakis(pentafluorophenyl)borate, 
tris(pentafluorophenyl)borane, lithium tetrakis(pentafluorophenyl)borate, 
triphenylcarbenium tetrakis(pentafluorophenyl)borate, and the like. In a 
particularly preferred embodiment, the pentafluorophenyl boron compound is 
a derivative of tetrakis(pentafluorophenyl)borate. Most preferably, the 
pentafluorophenyl boron compound is N,N-dimethyl-anilinium 
tetrakis(pentafluorophenyl)borate. 
Suitable non-limiting examples of the ether present in the crude mixture 
containing the pentafluorophenyl boron compound include methyl ether, 
diethyl ether, dipropyl ether, butylmethyl ether, diisopropyl ether, 
dibutyl ether, diisoamyl ether, dioxane, tetrahydrofuran and the like, as 
well as mixtures of any two or more of the foregoing. In a preferred 
embodiment, the ether is diethyl ether. In addition to the 
pentafluorophenyl boron compound, ether and water, the crude mixture 
typically will contain other impurities. These impurities are often 
byproducts from the synthesis of the pentafluorophenyl boron compound. The 
impurities present can depend upon the particular synthesis process which 
was employed. Typical non-limiting examples of impurities which may be 
present in the crude mixture include hydrogen chloride, 
N,N-dimethylanilinium chloride, fluorinated impurities such as 
bromopentafluorobenzene, chloropentafluorobenzene, hexafluorobenzene, and 
organic impurities such as N,N-dimethylaniline, oxidized dimethylanilinium 
derivatives, and alyl halides. 
The azeotropic organic solvent of this invention is capable of azeotrope 
formation with the water and has a boiling point above the boiling point 
of the ether. Suitable organic solvents include, for example, aliphatic 
hydrocarbons, aromatic hydrocarbons, alcohols, nitriles, esters, and 
ketones which are non-reactive with the pentafluorophenyl boron compound 
under the process conditions. Preferably, the azeotropic organic solvent 
is an aromatic hydrocarbon having 2 to 20 carbon atoms, and more 
preferably 5 to 10 carbon atoms. Non-limiting examples of suitable 
aromatic hydrocarbons include benzene, cumene, mesitylene, toluene, 
m-xylene, and the like, including mixtures of any two or more of the 
foregoing. In a particularly preferred embodiment, the azeotropic organic 
solvent is toluene. 
The aliphatic hydrocarbon used in preferred embodiments may be one or more 
cyclic or acyclic hydrocarbons, and the aliphatic hydrocarbon may be the 
same or different from the azeotropic organic solvent of this invention. 
Suitable aliphatic hydrocarbons are those which reduce the solubility of 
the pentafluorophenyl boron compound in the solution, thereby facilitating 
precipitation of the pentafluorophenyl boron compound. Preferably, the 
aliphatic hydrocarbon has from 5 to 16 carbon atoms in the molecule. 
Non-limiting examples of suitable saturated aliphatic hydrocarbons 
include, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, 
n-undecane, n-dodecane, n-tridecane, n-tetra-decane, n-pentadecane, 
2-methylpentane, 2,3-dimethylbutane, 2,4-dimethyl-5-butylnonane, 
cyclohexane and the like, including mixtures of any two or more of the 
foregoing. Less preferred are unsaturated aliphatic and cycloaliphatic 
hydrocarbons. Non-limiting examples of such unsaturated aliphatic and 
cycloaliphatic hydrocarbons include 1-pentene, 1-hexene, 1-heptene, 
1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 
1-tetradecene, 1-pentadecene, 2-pentene, 3-hexene, 3,4-dimethyl-2-hexene, 
1-hexyne, cyclohexene, and the like, including mixtures of any two or more 
of the foregoing unsaturated aliphatic hydrocarbons, or mixtures of any 
one or more of these unsaturated aliphatic hydrocarbons with any one or 
more of the foregoing saturated aliphatic hydrocarbons. More preferred are 
straight-chained saturated aliphatic hydrocarbons having 5 to 16 carbon 
atoms in the molecule. In a particularly preferred embodiment, the 
aliphatic hydrocarbon is n-pentane. 
The organic solvent of this invention may include aromatic hydrocarbons, 
halogenated aliphatic hydrocarbons, halogenated aromatic hydrocarbons, 
esters, ketones and nitriles, so long as the pentafluorophenyl compound is 
soluble in the organic solvent. Non-limiting examples of suitable organic 
solvents include chlorobenzene, bromoform, chloroform, dichloromethane, 
nitrobenzene, dibromomethane, acetonitrile, acetone, and the like, 
including mixtures of any two or more of the foregoing. Halogenated 
aliphatic hydrocarbons having 1 to 20 carbon atoms are preferred. 
Halogenated aliphatic hydrocarbons having 1 to 6 carbon atoms are more 
preferred, with dichloromethane being particularly preferred. 
As now may be appreciated, the processes of this invention require only a 
relatively small amount of process equipment in that all of the operations 
can be conducted in the same reaction vessel. In addition, this invention 
may be carried out as a batch, semi-continuous, or continuous process. 
Thus, if desired, each of the process steps may be conducted in a single 
reactor, such as a glass-lined reactor equipped with suitable distillation 
auxiliaries and agitators.

The following examples serve to illustrate this invention, but do not limit 
it. 
EXAMPLE 1 
Crude, wet N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate ether 
solution (20.0 grams, 15.9 wt %) was charged to a 50 mL distillation 
reactor. A total of 8.0 grams of diethyl ether and ethyl bromide was 
removed from the crude by distillation at 35.degree. C. (head temperature) 
and 53.degree. C. (jacket temperature), under pressure of 760 mm Hg over a 
period of 1 hour. Toluene (14.2 grams) was then added, and an additional 
total of 6.3 grams of diethyl ether, ethyl bromide, pentafluorobenzene, 
and toluene (90.2, 2.4, 0.3 and 6.8 GC area %, respectively) was removed 
by distillation at 48-60.degree. C. (head temperature) and 78-103.degree. 
C. (jacket temperature) over a period of 1.3 hours using the same 
pressure. A two-layer solution then was observed in the reactor. Toluene 
(32.0 grams) was again added to the reactor, and a total of 32.4 grams of 
diethyl ether, pentafluorobenzene and toluene (0.53, 0.14, and 99.2 GC 
area %, respectively) was removed by distillation at 82-110.degree. C. 
(head temperature), 117-125.degree. C. (jacket temperature) over a period 
of 2 hours using the same pressure. Another 10.0 grams of toluene were 
then added to the reactor, and a total of 13.6 grams of toluene (99.77 GC 
area %) and diethyl ether (0.06 GC area %) was removed by distillation at 
110.degree. C. (head temperature), 125-131.degree. C. (jacket temperature) 
over a period of 1 hour using the same pressure. The remaining solution 
was allowed to cool to 22-24.degree. C. and then 12 grams of pentane was 
added to the solution. A precipitate formed and was removed from the 
solution by filtration. A total of 3.3 grams of slightly off-white 
precipitate was recovered and shown to contain 98% N,N-dimethylanilinium 
tetrakis(pentafluorophenyl)borate by NMR analyses. This precipitate was 
then redissolved in 37 grams of warm dichloromethane at 32.degree. C., and 
the solution was then cooled to 22.degree. C., at which time another 16 
grams of pentane was added to the solution, while stirring. A white 
precipitate again formed and was removed from solution by filtration. 
After drying, the white precipitate weighed 3.0 grams (93.8% yield). By 
both F-NMR and H-NMR analysis (with trifluorobenzene internal standard), 
the white precipitate was determined to be 100% pure N,N-dimethylanilinium 
tetrakis(pentafluorophenyl)borate. Karl-Fisher analysis for water content 
showed 200 ppm of water present in the white precipitate, and the melting 
point of the white precipitate was determined by differential scanning 
calorimetry to be 225-226.degree. C. 
EXAMPLE 2 
To a distillation reactor was charged 10 grams of a ether solution 
containing 1 part (i.e., 1.65+/-0.05 grams) of crude, wet 
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, and 20 parts of 
toluene. The mixture was distilled at 110.degree. C. (head), 
125-134.degree. C. (oil-bath) over a period of 3 hours, during which 16 
parts of toluene, ether and water were removed. Then, 3 parts of pentane 
were added to the remaining solution (1 part N,N-dimethylanilinium 
tetrakis(pentafluorophenyl)borate and 4 parts toluene) and the solution 
was allowed to cool to 22.degree. C. A precipitate of 
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate formed and was 
removed by filtration. The precipitate was rinsed with 3 parts pentane. 
Upon drying, the precipitate was determined to weigh 1.7 grams. 
Dichloromethane (18.0 grams) was then added to the precipitate and the 
mixture was warmed to 35.degree. C. to dissolve the precipitate. Insoluble 
impurities were removed by filtration, and the solution was cooled to 
22.degree. C. Pentane (7.0 grams) was then added to the solution and a 
precipitate formed. The precipitate was removed by filtration and rinsed 
with 4 grams of pentane. Upon drying, the product weighed 1.5 grams 
(91+/-3% yield), and was snow-white in color. The product purity by F-NMR 
(with internal standard) was 101%. Purity by H-NMR (with internal 
standard) was 99%, with no ether present. 
EXAMPLE 3 
Crude N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (50.0 grams, 
84% pure) was stirred in 500 grams of dichloromethane under nitrogen at 
22.degree. C. for 30-60 minutes. The solution exhibited a green color, and 
solid impurity was removed by filtration. Then, 100-150 grams of pentane 
was added slowly over a period of 10 minutes under nitrogen at 22.degree. 
C. with stirring (using a magnetic bar). Fine N,N-dimethylanilinium 
tetrakis(pentafluorophenyl)borate precipitate was formed. The green 
impurity remained in solution. The precipitate was removed by filtration 
and was then rinsed with 100-150 grams of pentane. The yield of 
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate was approximately 
95%, and the purity was 96+%. 
EXAMPLE 4 
Crude N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (50.0 grams, 
84% pure) was stirred in 500 grams of dichloromethane under nitrogen at 
22.degree. C. for 30-60 minutes. The solution exhibited a green color, and 
solid impurity was removed by filtration. The remaining green solution was 
placed into an industrial blender. Then, 100-150 grams of pentane was 
added slowly over a period of 10 minutes under nitrogen at 22.degree. C. 
with low-speed stirring. Fine N,N-dimethylanilinium 
tetrakis(pentafluorophenyl)-borate precipitate was formed. The green 
impurity remained in solution. The precipitate was removed by filtration 
and was then rinsed with 100-150 grams of pentane. The yield of 
N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate was approximately 
95%, and the purity was 96+%. The average particle size was approximately 
22 microns. 
Comparative Example 
Crude, wet N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate (1 
gram), obtained by adding ether solution containing N,N-dimethylanilinium 
tetrakis(pentafluorophenyl)borate from the same source as that of Example 
1 to an equal volume of hexane, was filtered, and then dried under vacuum 
to obtain dry N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate. 
Karl-Fisher analysis for water content showed 2000 ppm of water present in 
the product, i.e., ten times the amount of water present in the product 
recovered in Example 1. 
The novel processes of this invention enable the isolation, purification 
and drying of pentafluorophenyl boron compounds in high yields and purity, 
with very low water content and average particle sizes of preferably no 
more than about 200 microns, more preferably no more than about 100 
microns, and most preferably no more than about 25 microns, all without 
the necessity of recrystallization, vacuum pumping or other additional, 
costly process steps. 
It is to be understood that the reactants and components referred to by 
chemical name or formula anywhere in the specification or claims hereof, 
whether referred to in the singular or plural, are identified as they 
exist prior to coming into contact with another substance referred to by 
chemical name or chemical type (e.g., another reactant, a solvent, or 
etc.). It matters not what chemical changes, transformations and/or 
reactions, if any, take place in the resulting mixture or solution or 
reaction medium as such changes, transformations and/or reactions are the 
natural result of bringing the specified reactants and/or components 
together under the conditions called for pursuant to this disclosure. Thus 
the reactants and components are identified as ingredients to be brought 
together in connection with performing a desired chemical reaction or in 
forming a mixture to be used in conducting a desired reaction. 
Accordingly, even though the claims hereinafter may refer to substances, 
components and/or ingredients in the present tense ("comprises", "is", 
etc.), the reference is to the substance, component or ingredient as it 
existed at the time just before it was first contacted, blended or mixed 
with one or more other substances, components and/or ingredients in 
accordance with the present disclosure. The fact that the substance, 
component or ingredient may have lost its original identity through a 
chemical reaction or transformation during the course of such contacting, 
blending or mixing operations is thus wholly immaterial for an accurate 
understanding and appreciation of this disclosure and the claims thereof. 
This invention is susceptible to considerable variation in its practice. 
Therefore the foregoing description is not intended to limit, and should 
not be construed as limiting, the invention to the particular 
exemplifications presented hereinabove. Rather, what is intended to be 
covered is as set forth in the ensuing claims and the equivalents thereof 
permitted as a matter of law.