Polymerization of ethylene using amido functional half‐sandwich complexes of group 4 metals

Ligands (C 13 H 9 )(2,6‐R 2 C 6 H 3 NH)SiPh 2 [R = i Pr (2a), Me (2b)] were synthesized by single deprotonation of the amino group in 2,6‐dialkylanilines with n ‐BuLi at −78°C followed by reaction with fluorenyl diphenyl silyl chloride [FluSi(Ph 2 )Cl]. Single crystal X‐ray diffraction studies revealed different geometries around the nitrogen atom for the two compounds. Titanium and zirconium complexes (3a–3d) were prepared by double deprotonation of the ligands with n ‐butyl lithium ( n ‐BuLi) followed by reaction with the respective metal chlorides, MCl 4 (THF) 2 . Polymerization of ethylene was performed using these complexes as catalyst precursors along with methylaluminoxane (MAO) as an activator at 5 bar pressure. Complexes 3a–3d/MAO exhibited moderate catalyst activities for polymerization of ethylene and resulted in high molecular weight linear poly(ethylene)s ( M v > 4 × 10 5 g/mol). Catalyst activities were much lower when compared to similar N ‐alkyl substituted complexes presumably due to the resonance effect of the aromatic group on the amido nitrogen. POLYM. ENG.SCI., 2011. © 2011 Society of Plastics Engineers