US Patent 6,153,777
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
A process of preparing in high yield racemic ansa-metallocene complexes by reacting a chelated bisamide group 4 metal complex with an ansa-bis-cyclopentodrenyl dianion reagent. The meso isomers are not detectable in the reaction product.
Jordan, Richard F. and Zhang, Xingwang Synthesis of ansa-metallocene catalysts. US Patent 6,153,777 filed November 02, 1999 and issued November 28, 2000. https://ir.uiowa.edu/patents/249