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

New ansa-zirconocene complexes with amino (8–11) and alkoxy (12) substituents attached to the η5-bonded indenyl fragment have been synthesized by the reaction of ZrCl4 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 η3-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.