Saturated bicyclic zirconium complexes by direct synthesis: old and new catalysts for olefin polymerisation

Metallocene complexes of Group IV metals1 are well established highly active catalysts for the homo- and co-polymerisation of ?-olefins, in particular if are of the ansa-bridged type. Indenyl and tetrahydroindenyl derivatives exhibit significant and interesting differences in polymerisation behaviour due to their steric and electronic properties. While the unsaturated derivatives are available by direct synthesis, their corresponding saturated counterparts usually require a catalytic hydrogenation step of already pre-formed metallocenes or can be prepared by complex syntheses, usually with low overall yields or with limited applicability3. We report here a new synthetic pathway2 that has proved successful for a versatile and "tuned" synthesis of a variety of bicyclic cyclopentadienyl ligands and their corresponding organometallic compounds (including also ansa-bridged and constrained geometry compounds), in good yields, with only minor purification steps, and reproducible in large-scale quantities.