Synthesis and X-ray structure of novel 2- and 3-heteroatom-substituted ansa-zirconocene complexes

Abstract

New ansa -zirconocene complexes with amino and alkoxy substituents attached to the η 5 -bonded indenyl fragment have been synthesized. Crystallographic analysis showed that heteroatom substituents, especially those in the 3-position on the indenyl ligand, have a substantial effect on the structure of metallocenes leading to an increase in the gap aperture in those complexes. New ansa -zirconocene complexes with amino ( 8 – 11 ) and alkoxy ( 12 ) substituents attached to the η 5 -bonded indenyl fragment have been synthesized by the reaction of ZrCl 4 with the appropriate dilithium salt in toluene. In addition to HRMS, NMR spectroscopy, and elemental analysis, all new metallocenes have been characterized by single crystal X-ray analysis. Crystallographic analysis showed that heteroatom substituents, especially those in the 3-position on the indenyl ligand, have a substantial effect on the structure of metallocenes leading to an increase in the gap aperture in those complexes. Slippage of the indenyl fragments toward η 3 -bonding was found to correlate with the electron donating ability of the substituent in the 3-position, being larger for amino than alkoxy substituents. Based upon the amount of slippage, 3-amino-substituted indenyl complexes bear strong resemblance to a fluorenyl complexes.