Silica Based Cocatalysts for Heterogeneous Olefin Dimerization and Ethene Polymerization Reactions with Nickel Complexes

摘要

We have developed a new buffered silica-based Lewis acid cocatalyst for olefin dimerization and polymerization reactions with nickel complexes. The Lewis acidities of EtAlCl2 and Et2AlCl-modified silicas were adjusted by the addition of BiPh3 or N-methylpyrrole buffers. The buffered heterogeneous cocatalysts were employed to activate nickel complexes for selective propene dimerization reactions to give dimers in 91?% yield. Buffer addition also reduced the rate of ligand abstraction from the catalytically active nickel center. In combination with a nickel diimine complex, ethene was polymerized to give 69 wt?% polyethylene and 31 wt?% oligomers. The polyethylene displayed a molecular mass of 154 kg?mol-1 and a polydispersity index (PDI) of 3.26. The oligomers consisted of 93?% butenes, 46?% thereof being 1-butene. Furthermore, triphenylbismuth-buffered Lewis acidic chloroaluminate ionic liquids were coated on surface-modified silica to yield a supported ionic liquid phase (SILP) system. Dimer selectivities of up to 94?% were obtained with the SILP system in nickel-catalyzed propene dimerization reactions. The newly developed silica-based cocatalysts provide promising new olefin dimerization systems suitable for fixed bed applications.