Synthesis and molecular structures of zirconium and hafnium complexes bearing dimethylsilandiyl-bis-2,4,6-trimethylindenyl and dimethylsilandiyl-bis-2-methyl-4,6-diisopropylindenyl ligands Vyacheslav V. Izmer a , Denis A. Sorokin a , Lyudmila G. KuzÕmina b , Andrei V. Churakov b , Judith A.K. Howard c , Alexander Z. Voskoboynikov a, * a Department of Chemistry, Moscow State University, V-234, Moscow 119899, Russian Federation b N. S. Kurnakov Institute of General and Inorganic Chemistry of Russian Academy of Sciences, 31, Leninskii pr., Moscow 119991, Russian Federation c Department of Chemistry, Durham University, South Road, Durham DH1 3LE, United Kingdom Received 19 June 2004; accepted 5 October 2004 Abstract Zirconium and hafnium ansa-complexes containing 2,4,6-trialkyl-substituted indenyl fragments were synthesized and unambig- uously characterized. Mixtures of rac- and meso-Me 2 Si(2-Me-4,6-R 2 C 9 H 3 -g 5 ) 2 MCl 2 , where R = Me, i-Pr and M = Zr, Hf, were obtained by a treatment of MCl 4 by dilithium salts of the respective bis(2,4,6-trialkylindenyl)dimethylsilanes in toluene. Alterna- tively, better yields of the same complexes can be obtained by the reaction between metal tetrachlorides and indenyl-tin derivatives gave the desired ansa-metallocenes. All rac- and meso-complexes of Zr and Hf were isolated in an analytically pure form, and six of these ansa-metallocenes were characterized by X-ray crystal structure analysis. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Zirconium; Hafnium; Metallocenes 1. Introduction Among chiral ansa-metallocenes the silylene-bridged bis-indenyl complexes with Me in position 2 have been most intensively studied because of their application for a-olefin polymerization [1]. Catalytic properties of these complexes depend strongly on type and position of substituents in the indenyl fragment. For instance, the complexes with 4-substituted (preferably aryl) inde- nyl ligands were found to have outstanding catalytic properties in the propene polymerization [2]. Ansa- metallocenes with 4,7-disubstituted indenyl ligands have been recently described [2–4]. Complexes with benzoannelated indenyl residue were prepared as well [2–8]. Meanwile, synthesis of the compounds with 4,6-disubstituted indenyl fragments has not been described so far. In this paper we report on convenient methods for the preparation of such 4,6-disubstituted indenes, the respective dimethylsilandiyl bridged ligands, and their ansa-complexes of zirconium and hafnium. 0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2004.10.052 * Corresponding author. Tel.: +7 095 939 4764; fax: +7 095 932 8846. E-mail address: voskoboy@org.chem.msu.ru (A.Z. Voskoboy- nikov). Journal of Organometallic Chemistry 690 (2005) 1067–1079 www.elsevier.com/locate/jorganchem