A strategy for the preparation of isolated organometallic catalysts on silica supports - Towards single-site solid catalysts

A well-defined amine functionalized silica surface displaying evidence of isolated amine sites is prepared using a molecular patterning technique. These aminosilicas serve as a support for immobilized organometallic catalysts, specifically constrained geometry catalysts for olefin polymerizations. The patterned catalysts show an activity of 27-32 kg polymer/mol Ti hr for the polymerization of ethylene with methylaluminoxane as cocatalyst. This activity is significantly higher than catalysts made via traditional supporting techniques on a densely loaded amine-functionalized silica, which show an activity of 4-10 kg polymer/mol Ti hr. This activity increase, when combined with reactivity and probe molecule studies, provides further evidence of the site-isolated behavior of the patterned amine sites and the unique nature of active sites that can be assembled on these aminosilica materials.