THE INFLUENCE OF STERIC AND ELECTRONIC EFFECTS OF SUBSTITUENTS ON THECYCLOPENTADIENYL RING ON THE BEHAVIOR OF (CPR)2TICL2 AND (CPR)CPTICL2ET3AL2CL3 CATALYSTS IN POLYMERIZATION OF ETHENE/

A range of (CpR)(CpR')TiCl2 complexes (R = R' = H, Me, Et, (i)Pr, (t)B u, SiMe3, CMe2Ph, CO2Me and R = H, R' = Me, (t)Bu, SiMe3, CMe2Ph, CO2M e) have been synthesized. Ethylene polymerization studies (50-degrees- C, 10 bar) in the presence of Et3Al2Cl3 as co-catalyst revealed cataly st activity of >20 g polyethylene (mol Ti h)-1 when the combined Tolma n cone angle for the two cyclopentadienyl rings was less than 260-degr ees and very low activity when the combined cone angle was larger. An analysis of available crystallographic data for (CpR)2TiCl2 complexes revealed that the Cl-Ti-Cl angle decreases as the size of R increases. It thus appears that the steric influence of R may affect polymerizat ion activity both by restricting access of reactants to the metal as w ell as by modifying metal-reactant (or polymer) interactions.