Zirconium allyl complexes as participants in zirconocene-catalyzed α-olefin polymerizations.

In a search for the hitherto elusive catalyst resting state(s) of zirconocene-based olefin polymerization catalysts, a combination of UV/Vis and NMR spectrometric methods reveals that polymer-carrying cationic Zr allyl complexes make up about 90 % of the total catalyst concentration. Other catalyst species that take part in the polymerization process have to be generated from this allyl pool into which they appear to relapse rather frequently.