Metathesis catalysts in confining reaction fields-confinement effects vs. surface effects

Abstract

It has been recognized previously that inside nanosized cavities like in mesoporous materials a small ensemble situation can be realized. The limited number of reactants per confinement leads to unusual chemical behaviour whenever inter- vs. intramolecular pathways compete against each other. Therefore, the metathesis reaction might represent a chemical process for which the product distribution is influenced by a confining reaction field. In the current paper we report about the unusual reactivity of the Grubbs generation I catalyst inside mesoporous silica materials. It has been observed that due to a combination of confinement and surface effects the Grubbs catalyst is not stable inside small pores. It quickly rearranges to a variety of unexpected products. However, the undesired deactivation of the catalyst can be prohibited by surface modification of the silica surfaces.