Studies in transition metal chemistry ; IV. The suitability of cyclopentadienylvanadium compounds as components of Ziegler-type polymerization catalysts

The polymerization of ethylene with Ziegler-type catalysts containing mono- and bis-cyclopentadienylvanadium compounds as constituents has been studied. The activities of these catalyst mixtures have been compared with those of two known highly active systems, viz. (i) the one based on biscyclopentadienyltitanium dichloride and aluminium alkyls and (ii) the one based on vanadium tetrachloride or vanadium oxytrichloride, respectively, and a large excess of aluminium alkyls. Under a wide variety of reaction conditions the cyclopentadienylvanadium compounds were found to be less active. Moreover, with vanadium, moderate activity was observed for systems based on monocyclopentadienyl derivatives and negligible to weak activity for mixtures based on biscyclopentadienyl derivatives. The large difference in suitability as catalyst constituents between the biscyclopentadienyl derivatives of titanium and of vanadium is discussed