Catalysts prepared via surface organometallic chemistry (SOMC) typically follow a classical synthetic route; the complexes with desired ligand design are first prepared homogenously via organometallic chemistry and then later grafted on metal oxide supports (SiO2, Al2O3, etc.). The end products usually retain its original molecular orientation after grafting and could then be used in catalysis reactions, for instance, supported pentamethyl-tungsten complexes in alkane methathsis. In other cases, modifications are still required after grafting as in the case of metal hydrides or metal carbenes. Yet, due to the difficulties in the preparation of air-, moisture sensitive, and/or possibly explosive organometallic complexes such as homogenous hexamethyl tungsten complex, direct grafting of these complexes is not the most feasible strategy in these cases. Moreover, some complexes cannot be prepared by classical organometallics methods due to intermetallic, functional group, and ligand interactions as reported by Wilkinson for certain methylated metal oxo species.These metal-oxo compounds could be very useful to obtain active robust catalysts. Therefore, one of the recommended solutions will be to support metal oxychloride complexes first on surface, and then modify the ligands around the metal center to obtain the desired oxo methylated complexes. Altering the classical strategy can resolve most of these problems, making a new series of well defined, active, easily prepared, and cheap catalysts. Due to the well-established reactivity of methyl ligand in SOMC, we will focus on surface alkylation of tungsten oxychloride. WOCl4 can be easily grafted on silica support dehydroxylated at 700oC SiO2 (700). Different alkylating agents are used in the next step to selectively alkylate the W-Cl bond without affecting the surface of the support and to get a well defined species. Later, the catalyst was tested in paraffin and olefin metathesis.

New well defined silica-supported tungsten oxo methyl synthesized by surface alkylation: Application in olefin and paraffin metathesis

248th National Meeting (2014)

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