rac-[ethylenebis(2-(thexyldimethylsiloxy)indenyl)]zirconium dichloride: synthesis, molecular structure and olefin polymerization catalysis

The synthesis and molecular structure of rac-[ethylenebis(2-(thexyldimethylsiloxy)indenyl)]zirconium dichloride (4), is reported. In combination with methylaluminoxane (MAO), 4 forms an active catalyst system for homogeneous polymerization of ethylene and propylene. The high activity of 4/MAO is retained at low [Al]:[Zr] ratios [(150-250):1]. Decreasing polymerization temperature or the [Al]:[Zr] ratio results in production of polyethylene having a high molecular weight shoulder in its molecular weight distribution (MWD). Deconvolution of the MWDs into a series of calculated Flory-distribution curves indicates that with this catalyst system ethylene is polymerized by three different types of active sites, whereas propylene is predominantly polymerized by two active sites. Complex 4 crystallizes in the indenyl-backward conformation. The ligand backbone adopts the expected C-2 symmetry. (C) 1998 Elsevier Science S.A. All rights reserved.