Heteroatom-substituted constrained-geometry complexes. Dramatic substituent effect on catalyst efficiency and polymer molecular weight

The new constrained-geometry complexes (CGC) [(eta (5)-C9H5X)(SiMe2-t-BU)TiR2 (X = 2-OEt (1a,b), 2-NMe2 (2a,b), 3-OMe (3a,b), 3-NC4H4 (4a,b); R = Cl, Me) have been synthesized with alkoxy and amino substituents attached to a second and third indenyl position. Four of the new complexes (1a-4a) have been characterized by single-crystal X-ray analysis. An ethylene-octene copolymerization study revealed an enormous substituent effect, both on the catalysts' activity and the molecular weight of produced polymers. The 3-amino-substituted complex 4b exhibits the highest catalytic activity and forms the highest molecular weight ethylene/octene copolymers that have ever been reported for this class of catalysts.