(η5-pentamethylcyclopentadienyl)tin(II) tetrakis(pentafluorophenyl)borate:: A new cocatalyst for the polymerization of α-olefins

The organotin. compound (eta(5)-pentamethylcyclopentadienyl)tin tetrakis(pentafluorphenyl)borate (1) has been synthesized from a reaction between (pentamethylcyclopentadienyl)tin chloride and lithium tetrakis(pentafuorophenyl)borate. This cation proved to be an effective Ziegler-Natta alpha-olefin cocatalyst. Activities for ethylene polymerizations using dimethylzirconocene and 1 were 7.3 x 10(5) g of PE/(mol of 1 .[C2H4]. h) at 20 degrees C and 1.2 x 10(6) g of PE/(mol of 1 .[C2H4]. h) at 70 degrees C. This system was also effective for the polymerization. of propylene. Activities using rac-ethylenebis(indenyl)dimethylzirconium with the tin cation were 3.0 x 10(5) g of PP/(mol of 1 .[C3H6]. 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 degrees C were 7.0 x 10(6) g of PE/(mol of 1 .[C2H4]. h). Activities for the polymerization of propylene using rac-ethylenebis-(indenyl)zirconium dichloride/tri(i-butyl)aluminum/1 at 20 degrees C were 5.4 x 10(6) g of PP/(mol of 1 .[C3H6]. h).