Novel Zirconocene Hydride Complexes in Homogeneous and in SiO₂‐Supported Olefin‐Polymerization Catalysts Modified with Diisobutylaluminum Hydride or Triisobutylaluminum

Abstract

Abstract Reactive species in SiO 2 ‐supported, zirconocene‐based olefin‐polymerization catalysts have been characterized by comparison of their UV‐vis spectra with those of related, NMR‐spectroscopically identified catalyst species in homogeneous solution. Neutral zirconocene dihydride complexes are found to arise in hydrocarbon solutions as well as on SiO 2 supports when catalyst systems that contain rac ‐Me 2 Si(ind) 2 ZrCl 2 and methylaluminoxane (MAO) are modified by addition of diisobutylaluminum hydride or triisobutylaluminum. These complexes, tentatively formulated as adducts with Lewis‐acidic alkylaluminum species AlR 2 X, rac ‐Me 2 Si(ind) 2 ZrH 2 · { n AlR 2 X}, are reconverted into the initial reactive zirconocene cations upon addition of isobutene to these reaction systems. magnified image