Abstract:
A process for preparing tetrakis (pentafluorophenyl) borate is described that involves reaction of a pentafluorophenyl magnesium halide with an alkali metal tetrafluoroborate.

Description:
This application is a continuation-in-part of Ser. No. 09/077,999 filed Jun. 15, 1998, now abandoned, which is the 35 U.S.C. §371 counterpart of application PCT/U.S.96/16390 filed Oct. 15, 1996. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the synthesis of tetrakis (pentafluorophenyl) borates by reaction of a tetrafluoroborate salt with a pentafluorophenyl compound. 
     BACKGROUND OF THE INVENTION 
     It is known to produce tetrakis (pentafluorophenyl) borates by reaction of boron trihalide with pentafluorophenyl lithium or pentafluorophenyl magnesium halide and by reaction of tris (pentafluorophenyl) boron with pentafluorophenyl lithium. See generally, published European patent application No. 0 604 961 A2 and U.S. Pat. No. 5,473,036. Such borates are important intermediates in the synthesis of catalysts used in combination with metallocene polymerization catalysts. 
     SUMMARY OF THE INVENTION 
     The invention provides a method for the production of tetrakis (pentafluorophenyl) borates by reacting a tetrafluoroborate salt with pentafluorophenyl magnesium halide in a non-interfering solvent. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Pentafluorophenyl magnesium halides (Grignards) are known. See, e.g., Respess, et al., J. Organometal. Chem. (1969) 18:263-274 and Respess, et al., J. Organometal. Chem. (1969) 19:191-195. Pentafluorophenyl magnesium halides useful in the invention have the formula C 6 F 6 MgX in which X is a halogen, e.g., iodine, chlorine or bromine, preferably bromine. 
     Tetrafluoroborate salts useful in the invention have the formula QBF 4  in which Q is sodium, lithium or potassium, preferably sodium. 
     The reaction between the Grignard and the tetrafluoroborate salt may be conducted in any non-interfering solvent. Typical solvents have the formula R—O—R′ in which the R and R′ are the same or different aliphatic hydrocarbon groups having 2-10 carbon atoms. Ethyl ether is preferred. The reaction is appropriately conducted at a temperature of 0° C. to 100° C., preferably at 30° C. to 35° C. 
     The tetrafluoroborate salt is added to the Grignard solution in stoichiometric amounts or in such greater or lesser amount as may be deemed appropriate. In the preferred practice of the invention the tetrafluoroborate salt is added in an amount more than 15% of stoichiometric.  Preferably the reaction mixture is refluxed to expedite the reaction. 
    
    
     EXEMPLIFICATION OF THE INVENTION 
     EXAMPLE I 
     A reaction vessel is changed with 0.25 mol of C 6 H 5 MgBr and 0.056 mol of NaBF 4  in an ethyl ether solvent. The reaction mixture is refluxed overnight under nitrogen. The reaction mixture was processed to recover 24.4 g of brown solids. Apparent yield 62.1%. 
       19 F NMR peaks established the presence of tetrakis (pentafluorophenyl) borate in an amount corresponding to approximately 50% of the total product of the reaction. 
     EXAMPLE II 
     Example I was repeated using NaBF 4  ground by pestle and mortar and a 36 hour reflux time. Yield: 62.2% of a product having a tetrakis (pentafluorophenyl) borate purity of about 60% as indicated by  19 F NMR.