Catalytic polymerization of propylene by heterobimetallic bridged early/late transition metal complexes

The polymerization of propylene was studied with a series of dinuclear early transition metal zirconocene-late transition metal complexes bridged by phosphido and arsenide moieties of general formula [(eta(5)-C5H4R ")(2)Zr{mu-ERR'}(2)M(CO)(n)] (E=P, R=R'=SiMe3, R "=H, M=Mo, n=4 (1); E=P, R=R'=SiMe3, R "=H, M=Ni, n=2 (2); E=As, R=R'=SiMe3, R "=H, M=Cr, n=4 (3); E=P, R=H, R'=2,4,6-i-Pr3C6H2, R "=Me, M=Mo, n=4 (4); E=P, R=H, R'=2,4,6-i-Pr3C6H2, R "=Me, M=Cr, n=4 (5)), as well as with the corresponding monometallic zirconocene precursor complexes of the type [(eta(5)-C5H4R ")(2)Zr(ERR')(2)] (E=P, R=R'=SiMe3, R "=H (6); E=P, R=H, R'=2,4,6-i-Pr3C6H2, R "=H (7)) and [(eta(5)-C5H4Me)(2)Zr(ERR')Cl] (E=P, R=H, R'=2,4,6-i-Pr3C6H2 (8)). The active cationic species were generated treating the complexes with an excess of methylalumoxane (MAO). The catalytic activity was found to be strongly dependent on temperature and catalyst/MAO ratio. (C) 1998 Elsevier Science B.V.