Helmut G. Alt

Dinuclear Transition Metal Complexes Consisting of an α-Diimine Complex Unit and a Half Sandwich Complex Unit as Dual Site Catalysts for the Polymerization of Ethylene

Dinuclear complexes consisting of an α-diimine complex unit with different ortho substituents at the aryl rings and a half sandwich complex unit were prepared, activated with methylaluminoxane (MAO) and tested for the polymerization of ethylene. The dinuclear catalysts bearing zirconium centers showed higher ethylene polymerization activities than the analogous titanium catalysts. Among the dinuclear catalysts with the same metal centers, the bulkier ortho substituents at the aryl moiety gave lower polymerization activities. The GPC spectra of the polyethylenes produced with the dinuclear catalysts displayed bimodal molecular weight distributions due to different active sites.

Transition Metal Complexes of Allylated α-Diimines as Self- Immobilizing Catalysts for the Polymerization of Ethylene

A series of allylated α-diimine complexes of Ti, Zr, V, Cr, Fe, Ni, and Pd was prepared and characterized. These complexes were activated with methylaluminoxane (MAO) and tested for catalytic ethylene polymerization. The allyl groups of the ligands can self-immobilize the catalysts and prevent reactor fouling. The catalyst activities and the properties of the obtained polyethylenes are influenced by the metal center and the structure of the corresponding catalyst. The allylated α-diimine nickel catalysts showed the highest activities in the series and produced polyethylenes with higher molecular weights compared to the analogous catalysts without allyl groups. The allylated α-diimine palladium catalysts showed no activities for ethylene polymerization.