The organotin compound (η 5 -pentamethylcyclopentadienyl)tin tetrakis(pentafluorophenyl)borate ( 1 ) has been synthesized from a reaction between (pentamethylcyclopentadienyl)tin chloride and lithium tetrakis(pentafluorophenyl)borate. This cation proved to be an effective Ziegler−Natta α-olefin cocatalyst. Activities for ethylene polymerizations using dimethylzirconocene and 1 were 7.3 × 10 5 g of PE/(mol of 1 ·[C 2 H 4 ]·h) at 20 °C and 1.2 × 10 6 g of PE/(mol of 1 ·[C 2 H 4 ]·h) at 70 °C. This system was also effective for the polymerization of propylene. Activities using rac- ethylenebis(indenyl)dimethylzirconium with the tin cation were 3.0 × 10 5 g of PP/(mol of 1 ·[C 3 H 6 ]·h). Activities increased markedly when using zirconocene dichlorides/tri( i -butyl)aluminum/ 1 . Activities for ethylene polymerization using zirconocene dichloride/tri( i -butyl)aluminum/ 1 at 20 °C were 7.0 × 10 6 g of PE/(mol of 1 ·[C 2 H 4 ]·h). Activities for the polymerization of propylene using rac- ethylenebis(indenyl)zirconium dichloride/tri( i -butyl)aluminum/ 1 at 20 °C were 5.4 × 10 6 g of PP/(mol of 1 ·[C 3 H 6 ]·h).
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Rhodes et al. (1998) studied this question.