Seven- and eight-membered saturated fused ring zirconium and titanium metallocenes: a route for the synthesis of elastomeric polypropylene

Unbridged zirconium and titanium catalysts, where a seven or eight-membered ring fused to a cyclopentadiene is associated with a phenyl substituent in position 2, were tested in propene polymerization in order to investigate the possibility to observe a "fluxional behavior", and to obtain stereoblock polypropylene, even in the absence of the aromatic ring, usually present in this kind of catalysts, by introducing the conformational flexibility of the saturated ring as a new parameter. The microstructure, molecular properties and thermal behavior of the polymers obtained showed that it is possible to observe a "fluxional behavior" even by replacing the basic indenyl structure with a slightly flexible saturated ring. Furthermore, this structural feature sensibly increases the stability of the complexes, thus making possible to observe for the first time the oscillating behavior in titanocenes.