Confinement of the Grubbs catalyst in alkene-functionalized mesoporous silica

Herein, we report on the impact of alkyl chain length of olefin moieties anchored into silica mesopores on the confinement behavior and stability of the first-generation Grubbs catalyst, i.e., [RuCl2 (=C(H)(Ph))(PCy3)(2)]. In this contribution, ordered mesoporous SBA-15 silica materials were functionalized with alkenyl-trichlorosilanes exhibiting different carbon chain lengths, e.g., vinyl- (C2), allyl- (C3), hexenyl- (C6) and octenyl- (C8) trichlorosilanes. Subsequently, the Grubbs I catalyst was incorporated into these different host materials in the presence of organic solvent. The thus-obtained materials, before and after interaction with Grubbs I, were characterized by a variety of methods, including N-2 physisorption, thermogravimetric analyses, solid state NMR (C-13, P-31, and Si-29) and attenuated total reflectance (ATR) infra-red spectroscopy. Our investigations reveal a pronounced dependence of the Grubbs surface stability as a function of the grafted alkyl chain length of the alkene moieties. The nature of the immobilized Ru-based species is function of the surface modification and the presence of residual silanol groups. (C) 2013 Elsevier Inc. All rights reserved.