Aluminum-based lewis acid cocatalysts for olefin polymerization

#This invention relates to the preparation of olefin polymers using ionic catalyst systems based on transition metal compounds activated by Lewis acids that are capable of providing stable polymerization catalysts.

#Group 13 based Lewis acids having three fluorinated aryl substituents are known to be capable of activating transition metal compounds into olefin polymerization catalysts. Trisperfluorophenylborane is demonstrated in EP 0 427 697 and EP 0 520 732 to be capable of abstracting a ligand for cyclopentadienyl derivatives of transition metals while providing a stabilizing, compatible noncoordinating anion. See also, Marks, et al, J. Am. Chem. Soc. 1991, 113, 3623-3625. The term “noncoordinating anion” is now accepted terminology in the field of olefin polymerization, both by coordination or insertion polymerization and carbocationic polymerization. See for example, EP 0 277 004, U.S. Pat. No. 5,198,401, and Baird, Michael C., et al, J. Am. Chem. Soc. 1994, 116, 6435-6436, and U.S. Pat. No. 5,668,234. The noncoordinating anions are described to function as electronic stabilizing cocatalysts, or counterions, for cationic metallocene complexes which are active for olefin polymerization. The term noncoordinating anion as used herein applies both to truly noncoordinating anions and coordinating anions that are at most weakly coordinated to the cationic complex so as to be labile to replacement by olefinically or acetylenically unsaturated monomers at the insertion site. The synthesis of Group 13-based compounds derived from trisperfluorophenylborane are described in EP 0 694 548. These Group 13-based compounds are said to be represented by the formula M(C6F5)3 and are prepared by reacting the trisperfluorophenylborane with dialkyl or trialkyl Group 13-based compounds at a molar ratio of “basically 1:1” so as to avoid mixed products, those including the type represented by the formula M(C6F5)nR3−n, where n=1 or 2. Utility for the tris-aryl aluminum compounds in Ziegler-Natta olefin polymerization is suggested.

#Perfluorophenylaluminum (toluene) has been characterized via X-ray crystallography. See, Hair, G. S., Cowley, A. H., Jones, R. A., McBurnett, B. G.; Voigt, A., J. Am. Chem. Soc., 1999, 121, 4922. Arene coordination to the aluminum complex demonstrates the Lewis acidity of the aluminum center. However, perfluorophenyl-aluminum complexes have been implicated as possible deactivation sources in olefin polymerizations which utilize Trityl+ B(C6F5)4−/alkylaluminum combinations to activate the catalysts. See, Bochmann, M.; Sarsfield, M. J.; Organometallics 1998, 17, 5908. Bochmann and Sarsfield have shown that Cp2ZrMe2 reacts with Al(C6F5)30.5(toluene) with transfer of the C6F5— moiety forming metallocene pentafluorophenyl complexes. These complexes were reported having very low activity compared to the corresponding metallocene dimethyl complexes when activated with B(C6F5)3 or Trityl+0 B(C6F5)4−.

#The following examples are presented to illustrate the foregoing discussion. All parts, proportions and percentages are by weight unless otherwise indicated. All examples were carried out in dry, oxygen-free environments and solvents. Although the examples may be directed to certain embodiments of the present invention, they are not to be viewed as limiting the invention in any specific respect. In these examples certain abbreviations are used to facilitate the description. These include standard chemical abbreviations for the elements and certain commonly accepted abbreviations, such as: Me=methyl, THF, or thf=tetrahydrofuran, and Cp*, permethylated cyclopentadienyl metal ligand.

#All molecular weights are weight average molecular weight unless otherwise noted. Molecular weights (weight average molecular weight (Mw) and number average molecular weight (Mn) and (Mz) were measured by Gel Permeation Chromatography (GPC) as described below.

#Examples 1 to 4 Mw/Mn determinations were measured using a Waters 150 Gel Permeation Chromatograph equipped with a differential refractive index detector and calibrated using a broad calibration based on SRM-1475 (a linear Polyethylene standard obtained from NBS). Samples were run in 1,2,4-trichlorobenzene at 145° C. with a concentration of 1.5 mg/ml. The injection volume was 300 μl. The column set was three Shodex GPC AT-806 MS columns in series. This general technique is discussed in “Liquid Chromatography of Polymers and Related Materials III”, J. Cazes Ed., Marcel Decker, 1981, Page 207.