New Direct Syntetic Method For Group IV Tetrahydroindenyl-Type Fused Bicyclic Complexes

Metallocene complexes of Group IV metals having ansa-bridged ligands1 are well established highly active co-catalysts for the homo- and co-polymerisation of ?-olefins. Tetrahydroindenyl derivatives can be more effective co-catalysts than the parent unsaturated derivatives, particularly for the incorporation of co- and ter-monomers2. Moreover, it appears that the hydrogenation modifies the steric and electronic properties of these metallocenes leading to a greater resistance to hydrolysis. The unsubstituted indenyl and fluorenyl ligands are directly available, whilst the normal route tetrahydroindenyl ligands is via the catalytic hydrogenation of the corresponding unsaturated indenyl complexes3. The synthesis of tetrahydroindenyl-type ligands prior to their attachment to the transition metal have been explored by others4 and elegant synthetic routes have been found. However, often the overall yields were low or the method used was of limited applicability. We report here a versatile and flexible route to tetrahydroindenyl systems and to related ligands containing larger saturated ring systems attached to the cyclopentadienyl ring starting from readily available cycloalkanones.