Ethylene oligomerization catalyzed by a novel iron complex containing fluoro and methyl substituents

A novel 2,6-bis(imino)pyridyl iron complex, [2,6-(2-F-4-CH ₃C ₆H ₃N=CCH ₃) ₂C ₅H ₃N]FeCl ₂·H ₂O (3) has been synthesized by the reaction of the corresponding bis(imino)pyridyl ligand with FeCl ₂·4H ₂O in tetrahydrofuran (THF). The activity of complex 3 reaches to 10 ⁷ g/mol Fe h in ethylene oligomerization, and the products are mostly (>90%) 1-butene, 1-hexene and 1-octene. As reaction temperature increases, the activities decrease rapidly and the product distributions shift to the low-molecular-weight part. The product distributions are almost unchanged when the Al/Fe molar ratio increases from 420 to 2500, but the catalytic activities increase rapidly at first and then decrease. Other three complexes {2,6-(2-X-4-Y-6-ZC ₆H ₃N=CCH ₃) ₂C ₅H ₃N}FeCl ₂· nH ₂O (X = CH ₃, Y = CH ₃, Z = H, n = 0 (1), X = F, Y = H, Z = F, n = 1 (2)) and {Fe[2,6-(2-FC ₆H ₃N=CCH ₃) ₂C ₅H ₃N] ₂} ²⁺[FeCl ₄] ^2-·H ₂O (4) have been also synthesized for comparison and used for ethylene oligomerization. The ortho and para substituents on aniline have performed effects on oligomerization activities and distributions of oligomers for 2,6-bis(imino)pyridyl iron complexes.