Preparation of High-Purity Ammonium Tetrakis(pentafluorophenyl)borate for the Activation of Olefin Polymerization Catalysts

Homogeneous olefin polymerization catalysts are activated in situ with a co-catalyst ([PhN(Me)(2)-H](+)[B(C(6)F(5))(4)](−) or [Ph(3)C](+)[B(C(6)F(5))(4)](−)) in bulk polymerization media. These co-catalysts are insoluble in hydrocarbon solvents, requiring excess co-catalyst (>3 eq.). Feeding the activated species as a solution in an aliphatic hydrocarbon solvent may be advantageous over the in situ activation method. In this study, highly pure and soluble ammonium tetrakis(pentafluorophenyl)borates ([Me(C(18)H(37))(2)N-H](+)[B(C(6)F(5))(4)](−) and [(C(18)H(37))(2)NH(2)](+)[B(C(6)F(5))(4)](−)) containing neither water nor Cl(−) salt impurities were prepared easily via the acid–base reaction of [PhN(Me)(2)-H](+)[B(C(6)F(5))(4)](−) and the corresponding amine. Using the prepared ammonium salts, the activation reactions of commercial-process-relevant metallocene (rac-[ethylenebis(tetrahydroindenyl)]Zr(Me)(2) (1-ZrMe(2)), [Ph(2)C(Cp)(3,6-(t)Bu(2)Flu)]Hf(Me)(2) (3-HfMe(2)), [Ph(2)C(Cp)(2,7-(t)Bu(2)Flu)]Hf(Me)(2) (4-HfMe(2))) and half-metallocene complexes ([(η(5)-Me(4)C(5))Si(Me)(2)(κ-N(t)Bu)]Ti(Me)(2) (5-TiMe(2)), [(η(5)-Me(4)C(5))(C(9)H(9)(κ-N))]Ti(Me)(2) (6-TiMe(2)), and [(η(5)-Me(3)C(7)H(1)S)(C(10)H(11)(κ-N))]Ti(Me)(2) (7-TiMe(2))) were monitored in C(6)D(12) with (1)H NMR spectroscopy. Stable [L-M(Me)(NMe(C(18)H(37))(2))](+)[B(C(6)F(5))(4)](−) species were cleanly generated from 1-ZrMe(2), 3-HfMe(2), and 4-HfMe(2), while the species types generated from 5-TiMe(2), 6-TiMe(2), and 7-TiMe(2) were unstable for subsequent transformation to other species (presumably, [L-Ti(CH(2)N(C(18)H(37))(2))](+)[B(C(6)F(5))(4)](−)-type species). [L-TiCl(N(H)(C(18)H(37))(2))](+)[B(C(6)F(5))(4)](−)-type species were also prepared from 5-TiCl(Me) and 6-TiCl(Me), which were newly prepared in this study. The prepared [L-M(Me)(NMe(C(18)H(37))(2))](+)[B(C(6)F(5))(4)](−)-, [L-Ti(CH(2)N(C(18)H(37))(2))](+)[B(C(6)F(5))(4)](−)-, and [L-TiCl(N(H)(C(18)H(37))(2))](+)[B(C(6)F(5))(4)](−)-type species, which are soluble and stable in aliphatic hydrocarbon solvents, were highly active in ethylene/1-octene copolymerization performed in aliphatic hydrocarbon solvents.