New titanium(IV) complexes having two bidentate β-iminoethyl-spiro[4,5]decan-6-onato ligands with various N-aryl substituents have been synthesized. X-ray crystal structure analysis reveals that these titanium complexes all exhibit a C2-symmetric conformation with a distorted octahedral geometry, although the specific orientation of the ligands around the titanium center varies with the identity of the N-aryl moiety. Upon activation with methylaluminoxane (MAO), these complexes catalyze the polymerization of ethylene and propylene. In the case of ethylene, most complexes exhibit the characteristics of a living polymerization between 0 °C and 25 °C, producing polyethylenes with narrow molecular weight distributions and number average molecular weights up to 100 000 g/mol. Depending on the N-aryl substituents, polymerizations of propylene result in products with tacticity ranging from slightly syndiotactic to slightly isotactic.
