Organic compounds -- part of the class 532-570 series – Organic compounds – Boron containing
Reexamination Certificate
2001-05-18
2002-11-05
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Boron containing
C568S001000
Reexamination Certificate
active
06476271
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods for preparing tetrakis(pentafluorophenyl) borate salts used in conjunction with metallocene catalysts for olefin polymerization. More specifically, the present invention relates to novel methods for making trityl tetrakis(pentafluorophenyl) borate that is substantially free of ether and other oxygenated contaminants, and the tetrakis(pentafluorophenyl) borate salts used in its preparation.
BACKGROUND OF THE INVENTION
Boron co-catalysts and their metallocene catalyst counterparts are highly effective in the polymerization of ethylene and propylene. Both components of such catalyst systems need to be free of contaminants that would interfere with the polymerization process since they are used at very low levels, compared to the weight of the monomer used in the reaction. Such contaminants include Lewis bases (substances that donate a pair of electrons). Therefore, safe and reliable processes for the manufacture of high purity trityl tetrakis(pentafluorophenyl) borate are desirable. More preferred are manufacturing processes for trityl tetrakis(pentafluorophenyl) borate that provide a product having consistent color and high purity. It has been determined that, with respect to purity, it is most desirable for trityl tetrakis(pentafluorophenyl) borates to be substantially free of ether (less than 0.5 wt %) and other oxygenated contaminants such as water.
There are few known methods for making trityl tetrakis(pentafluorophenyl) borate. One method, as described in U.S. Pat. No. 5,399,781, involves reacting lithium tetrakis(pentafluorophenyl) borate with trityl chloride in an alkane. This process yields, at least in part, trityl tetrakis(pentafluorophenyl) borate. Further, such processes described in the U.S. Pat. No. 5,399,781 patent can be achieved in the absence of ether solvents. In addition, the process for making the required starting material lithium tetrakis(pentafluorophenyl) borate can also be achieved in the absence of ether solvents. However, pentafluorophenyl lithium, from which lithium tetrakis(pentafluorophenyl) borate is made, is hazardous and must therefore be handled at low temperatures. This significantly complicates the process, ultimately affecting process costs. Thus, while suitable for small-scale laboratory operations, the above-described lithium tetrakis synthesis is not desirable for large-scale manufacture.
Sodium and potassium tetrakis(pentafluorophenyl) borates are known. The use of these materials for the preparation of trityl tetrakis(pentafluorophenyl) borate is suggested in EP 0 913 400 A1, although no experimental data was provided specifically for the preparation of the trityl borate. One method of preparing the potassium salt is known (A. G. Massey and A. J. Park,
J. Organometallic Chem.,
2 (1964) 245), but again, this method utilizes the lithium salt. Therefore, for the reasons already explained above, this method offers no better solution to the problem.
Mitsui et al. (EP 0 913 400 A1, 1999) describe the conversion of (C
6
F
5
)
4
BMgBr into the corresponding sodium salt. The bromomagnesium salt can be made more safely by using the Grignard reagent, C
6
F
5
MgBr. However, the conversion of the magnesium salt to the corresponding alkali metal borates involves treating the magnesium salt (in ether-toluene) with an aqueous solution of a sodium carboxylate, and extracting the aqueous layer with ethyl acetate. Although the purity of the desired sodium salt was acceptable according to fluorine NMR analysis, no indication was given as to the presence of residual solvents in the product.
In addition to the hazards associated with the use of pentafluorophenyl lithium, the crude mixture of LiCl and trityl tetrakis(pentafluorophenyl) borate was described in the prior art as a yellow solid. However, after removing the LiCl, the supposedly “purified” product was not yellow, but was orange in color (an observation also made by Chien et al. who used the same process (
J. Am. Chem. Soc.,
113 (1991) 8570)). The change in color from yellow to orange in these prior art preparations of trityl tetrakis(pentafluorophenyl) borate is taken as an indication of the presence of the residual polar materials in the final product.
Prior art preparations of solid trityl tetrakis(pentafluorophenyl) borate have been isolated by removing methylene chloride solvent from the borate solution. If the removal of the last amount of the methylene chloride is vacuum assisted, the product tends to “bloom” or foam up, filling the entire vessel. Once the solvent is removed, the foamed trityl product is difficult to remove from the reaction vessel. This foaming inhibits the use of this process on a large scale.
As shown below in the Comparative Example section, when sodium tetrakis(pentafluorophenyl) borate is made according to EP 0 913 400 A1, ethyl acetate is clearly present as evidenced by proton NMR analysis. This illustrates the difficulty of removing coordinating contaminants from tetrakis(pentafluorophenyl) borate salts. In fact, this European patent discloses many ether complexes of borate salts, again indicative of the strong bond between the borate salts and ethers.
Thus, a safe, repeatable, and scaleable method for preparing trityl tetrakis(pentafluorophenyl) borate of consistent color and purity, while being essentially free of ether and other oxygen contaminants, is not known.
SUMMARY OF THE INVENTION
In accordance with one embodiment, the present invention relates to producing sodium or potassium tetrakis(pentafluorophenyl) borate that is substantially free of ether and other organic contaminants containing oxygen atoms. In a second embodiment, the invention relates to a method for producing trityl tetrakis(pentafluorophenyl) borate from the corresponding alkali metal salt.
More specifically, the present invention relates to a method for making lithium, sodium or potassium tetrakis(pentafluorophenyl) borate that is substantially free of ether and other organic contaminants containing oxygen atoms from a pentafluorophenyl magnesium bromide compound. Preferably, the (pentafluorophenyl) magnesium bromide is reacted in an ether solvent with a tris(pentafluorophenyl) borane in an aromatic hydrocarbon solvent to produce tetrakis(pentafluorophenyl) borate magnesium bromide. The tetrakis(pentafluorophenyl) borate magnesium bromide is then reacted with an aqueous solution of a halide selected from the group consisting of sodium chloride and potassium chloride to create an organic phase containing a product compound selected from the group consisting of tetrakis(pentafluorophenyl) borate sodium salt and tetrakis(pentafluorophenyl) borate potassium salt. The organic phase is separated, and the solvent is removed from the organic phase to provide a substantially ether-free compound selected from the group consisting of sodium tetrakis(pentafluorophenyl) borate and potassium tetrakis(pentafluorophenyl) borate. Most preferably, the product compound comprises less than about 0.5 weight percent ether.
In accordance with a further embodiment, the present invention relates to the manufacture of trityl tetrakis(pentafluorophenyl) borate by first providing a substantially ether-free compound selected from the group consisting of sodium tetrakis(pentafluorophenyl) borate and potassium tetrakis(pentafluorophenyl) borate. The substantially ether-free compound is then reacted with a trityl halide in a hydrocarbon liquid to form a slurry of trityl tetrakis(pentafluorophenyl) borate and a halide in a hydrocarbon liquid. The trityl tetrakis(pentafluorophenyl) borate and halide is then separated from the hydrocarbon liquid by a suitable method, such as filtration or decantation, followed by dissolving the trityl tetrakis(pentafluorophenyl) borate in a halogenated solvent to form a solution, said solvent not containing oxygen, nitrogen or other coordinating atoms. The trityl tetrakis(pentafluorophenyl) borate solution is then diluted in a hydrocarbon solvent having a higher boiling point than the halogenated solvent. Finally, the halogenat
Chess Deborah
Honeywell International , Inc.
Szuch Colleen
Vollano Jean F.
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