Multifluoro-Modification Enhancing Catalytic Activity and Thermal Stability of Bis(imino)pyridylcobalt Chlorides for Linear Polyethylene.

Abstract

The multifluoro aniline, 2,6-bis[bis(4-fluorophenyl)methyl]-4-trifluoromethoxy-phenylamine, is meticulously synthesized and utilized to form a series of bis(imino)pyridine derivatives. These derivatives react with cobalt chloride to give six bis(imino)pyridylcobalt (II) complexes (alkyl: 2,6-dimethyl Co1; 2,6-diethyl Co2; 2,6-diisopropyl Co3; 2,4,6-trimethyl Co4; 2,6-diethyl-4-methyl Co5; 2,6-bis[bis(4-fluorophenyl)methyl]-4-trifluoromethoxy Co6). High activity and good thermal stability in ethylene polymerization are achieved by these cobalt complexes in the presence of MAO or MMAO. Notably, superior polymerization results are observed in n-hexane compared to toluene with peak activity reaching 1.55×10⁷ g (PE) mol^-1 (Co) h^-1 at 70 °C in n-hexane. Moreover, the resulting polyethylenes are highly linear, featuring vinyl terminal group, and exhibit a wide range of molecular weights (M_w: 22.5-285 kg mol^-1) along with high melting points (T_m >127.3 °C).