Fluorinated cobalt catalysts and their use in forming narrowly dispersed polyethylene waxes of high linearity and incorporating vinyl functionality

A family of six bis(arylimino)pyridine-cobalt(ii) chloride complexes, [2-{CMeN(2-F-4,6-((4-FC H ) CH) C H )}-6-(CMeNAr)C H N]CoCl (Ar = 2,6-Me C H Co1, 2,6-Et C H Co2, 2,6-i-Pr C H Co3, 2,4,6-Me C H Co4, 2,6-Et-4-MeC H Co5) and [2-[CMeN{2-{(4-FC H ) CH}-4-{CH(C H )Ar }-6-F}]-6-(CMeN(2,6-i-Pr C H ))C H N]CoCl (Ar = (3-(4-FC H ) CH-4-NH -5-F)C H ) (Co6), each incorporating oneortho-fluoride and oneortho-bis(4-fluorophenyl)methyl group, has been synthesized in good yield from the corresponding unsymmetricalN,N,N′-ligands,L1-L6. All complexes have been well characterized including by F NMR spectroscopy; a variable temperature F NMR study has also been performed onCo6to investigate a dynamic isomerization process. The molecular structures ofCo1andCo5emphasize the variation in steric protection of the metal center imparted by the inequivalentN-aryl groups. In the presence of methylaluminoxane (MAO) or modified methylaluminoxane (MMAO),Co1-Co5exhibited high activities of up to 11.7 × 10 g of polyethylene (PE) (mol of Co) h at 70 °C, delivering strictly linear, low molecular weight PE waxes (between 924 and 5550 g mol ) of narrow dispersity and terminated with vinyl functionality. By comparison,Co6, possessing a more extended fluorinatedpara-CH(C H )Ar group, was the least active but afforded the highest molecular weight polyethylene (up to 10 027 mol ). In addition, DFT studies of the model Co(i)-propyl species,Co1′,Co3′andCo6′, have been performed in an attempt to explain the favorable formation of the low molecular weight polymers. 6 4 2 2 6 2 5 3 2 2 6 3 2 6 3 2 6 3 3 6 2 6 2 6 4 2 6 5 2 6 3 5 3 2 6 4 2 2 6 2 6 5 F F 19 19 6 −1 −1 −1 F −1