Lewis acid-catalysis plays an important role throughout the chemical value chain. One example concerns the systems based on TiIV as selective epoxidation catalysts. However, until today, the true nature of the active site is poorly understood for immobilized systems. Therefore, the development of well defined model catalysts is desirable in order to compare the chemistry of different surface species.Chemical Vapor Deposition (CVD) is a convenient approach to synthesize heterogeneous catalysts in a very precise way. This solvent-free technique moreover matches the sustainable and environmentally friendly technological demands of today. The reaction of a volatile metals precursor (e.g., TiCl4, Ti(O-iprop)4, VOCl3) with silanol-groups on a support (e.g., silica) creates chemically bound sites on the surface which can be further modified by post-synthesis procedures. The same can be done by using a solvent to anchor non-volatile metal precursor (e.g. ZrCl4). In order to characterize the resulting catalyst a variety of spectroscopic tools have been developed (ranging from 35Cl solid state NMR to ligand probing) to elucidate the active sites and therewith setting the starting point for drawing conclusions about the chemical mechanism of the underlying reaction.In this contribution, we present a convenient way to synthesize silica-supported d0 transition metal catalysts which are chemically modified by post-synthesis methods and characterized by various techniques. Finally a general mechanism will be presented in which the change of the surface metal species can be tuned upon post-synthesis heat treatment.

Thermal restructuring of d<sup>0</sup> transition metal Lewis acid sites grafted to silica

244th National Meeting (2012)

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Thermal restructuring of d0 transition metal Lewis acid sites grafted to silica

Thermal restructuring of d⁰ transition metal Lewis acid sites grafted to silica