Ethylene polymerization with silica-supported bis(imino)pyridyl iron(II) catalysts

Two strategies have been developed to prepare silica-supported bis(imino)pyridyl Fe(II) catalysts for ethylene polymerization. The bis(imino)pyridyl ligands were modified by the introduction of reactive ethoxysilane or Sisingle bondCl end groups, allowing the immobilization of them via the direct reaction of the ethoxysilane or Sisingle bondCl groups with the silanols on the silica surface. The resultant silica-supported bis(imino)pyridyl ligands were characterized by analytical and spectroscopic (NMR, Raman, FTIR, and XPS) techniques. The complexation reactions of the supported ligands with FeCl2 ⋅ 4H2O give rise to silica-supported Fe(II) precatalysts, which exhibit high catalytic activities for ethylene polymerization in the presence of modified methylaluminoxane (MMAO). The molecular weights of the polyethylenes obtained with the supported precatalysts are much higher than those produced with corresponding homogeneous Fe(II) precatalyst under the same conditions.