Synthetic Explorations Towards Sterically Crowded 1,2,3‐Substituted Bis(indenyl)zirconium( IV ) Dichlorides

The systematic synthesis of 1,3‐dialkyl‐substituted 2‐silylindenes and their suitability as zirconocene ligands is discussed. Unexpected reactivities rendered a number of substitution patterns unfeasible, especially for alkyl groups other than methyl in 2‐(trimethylsilyl)indene derivatives, and essentially for all derivatives of 2‐(dimethylsilyl)indene. The syntheses of rac / meso ‐bis[1‐methyl‐2‐(trimethylsilyl)indenyl]zirconium( IV ) dichloride ( 12 ) and bis[1,3‐dimethyl‐2‐(trimethylsilyl)indenyl]zirconium( IV ) dichloride ( 13b ) are described. The solid‐state structure of the latter displays strong deformations within the ligand framework and an unusually large Cp centroid ‐Zr–Cp centroid angle. Both, 12 /MAO and 13b /MAO, displayed ethene and ethene‐co‐1‐hexene polymerization activity. Curiously, 13b /MAO shows an extraordinary monomer selectivity, which can be rationalized by means of DFT calculations on the active site. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)