Reza Teimuri-mofrad - Department of Organic Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, I. R. Iran.
Ramin Farazmand - Department of Organic Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, I. R. Iran.
Ali Akbar Entezami - Department of Organic Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz, I. R. Iran.

The C2-symmetric ansa-metallocenes containing a bis (indenyl) ligand are the best studied and most common of all of the metallocene polymerization catalysts [1-2]. This ispartly due to the flexibility offered by the indenyl ligands in these systems, which can be substituted to change thestructural framework of the resulting metallocene catalyst. In other words, metallocene catalysts can be tuned to produce polypropylene with tacticity ranging from perfectly isotactic to completely atactic by changing the ligand framework around the central metals [3].