DISILOXANE BRIDGED INDENYL METALLOCENE CATALYSTS FOR OLEFIN POLYMERIZATIONS

Two new disiloxanyl-bridged bis(indenyl) Group 4 metallocenes, [rac-1,3-bis(eta(5)-indenyl)-1,1,3,3-tetramethyldisiloxane]dichlorotitamium (2) and -zirconium (3), have been synthesized from the corresponding ligand 1,1,3,3-tetramethyl-1,3-bis(indenyl)disiloxane (5), which in turn was obtained by the hydrolysis of (1-indenyl)chlorodimethylsilane (4). Both 2 and 3 exhibit unusual and unexpected catalysis behaviors for olefin polymerization. They polymerize ethylene only when activated by methyl aluminoxane (MAO) but not by Ph(3)C(+)B(C6F5)(4)(-)-tri-isobutylaluminum (7). The Ti precursor 2 does not polymerize propylene with either cocatalyst, whereas the Zr precursor 3 exhibited moderate activity to produce atactic polypropylene, even though 3 is C, symmetric. The propylene polymerization activities of 3-MAO increased strongly while that of 3-7 decreased slightly with the increase in T-p. These catalytic behaviors may be the result of sigma donation from oxygen atom of the siloxane bridge to metal center.