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

Zirconium and hafnium ansa-complexes containing 2,4,6-trialkyl-substituted indenyl fragments were synthesized and unambiguously characterized. Mixtures of rac- and meso-Me2Si(2-Me-4,6-R2C9H3-η5)2MCl2, where R = Me, i-Pr and M = Zr, Hf, were obtained by a treatment of MCl4 by dilithium salts of the respective bis(2,4,6-trialkylindenyl)dimethylsilanes in toluene. Alternatively, 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.