Preparation of chiral metallocene dihalides

Claim 1

A process for preparing a chiral metallocene dihalide compound comprising reacting a compound represented by the formula: ##STR3## wherein both R 1 and R 2 , which can be the same or different, represent a hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl, or arylalkyl radicals having from 1 to 20 carbon atoms, and R 2 also represents hydrogen, or R 1 and R 2 are joined together with the two carbon atoms of the cyclopentadienyl ring form a C 4 -C 6 ring; with potassium hydride followed by condensation with MX 4 or its bis(tetrahydrofuran) adduct, wherein X is a halogen selected from the group consisting of chlorine, bromine and iodine, and M represents zirconium or hafnium, except M is not zirconium when X is bromine, and recovering the resulting product.