Synthesis of Novel Complex with Bridged Bis(indenyl) Ligand and its Polymerization Behavior of Propylene

Novel ansa-zirconocenes characterized by a bis(indenyl) ansa ligand bridged between 4 and 4’ positions were synthesized. The behavior of these complexes as polymerization catalysts in the presence of methylalumoxane and properties of the polymers thus obtained were studied. Isotactic polypropylene was obtained by using C₂-symmetrical zirconocene. Especially, rac-Me₂Si[4,4’-(3-methyl-1-phenylindenyl)₂]ZrCl₂ produced polypropylene with high tacticity, and a small amount of 3,1-type regiodefect. By the polymerization test with above complex at various propylene pressures, the depression of melting point of polymer was observed with decrease of monomer pressure, which seemed to be due to the lowering of isotacticity mainly. And by the plot of 1/P_Nversus 1/[propylene], we got a relatively large value of k_TO/k_P, and it is suggested that β-H transfer to propylene was not suppressed by substituent at 3 position effectively. Changing substituent at 3 position from methyl group to ethyl group resulted in increasing of molecular weight of polymer.