Synthesis of an oxo trialkyl tungsten fluoride complex and its dual reactivity with silica dehydroxylated at high temperature

Abstract
The novel complex W (=O)Np3F has been prepared by fluorination of the corresponding chloride counterpart with AgBF4. The reactivity of this complex with silica dehydroxylated at 700 °C afforded a well-defined silica supported monopodal tungsten oxo trialkyl surface species (≡SiO)W (=O)Np3. The reaction proceeds both through silanolysis of the W-F bond and opening of a siloxane bridge, with formation of a Si-F fragment, thanks to the affinity of silicon for fluoride. The resulting surface species was characterized by elemental analysis, DRIFT, solid state NMR and EXAFS spectroscopy. This material presenting fluorine on its surface shows an enhanced catalytic activity in propylene self-metathesis compared to its monopodal counterpart (≡SiO)W (=O)Np3 (prepared from W (=O)Np3Cl) suggesting that the Si-F in a close vicinity to the W decreases the electron density of the W and thus increases its reactivity towards the olefinic substrate.

Citation
Merle N, Mazoyer E, Szeto KC, Rouge P, de Mallmann A, et al. (2018) Synthesis of an oxo trialkyl tungsten fluoride complex and its dual reactivity with silica dehydroxylated at high temperature. Journal of Organometallic Chemistry. Available: http://dx.doi.org/10.1016/j.jorganchem.2018.05.016.

Acknowledgements
E. Mazoyer thanks UOP for a graduate fellowship. This work was funded by the Agence Nationale de la Recherche (ANR-12-BS07-0021-01, OXOCAT). CNRS, We also thank Steven Fiddy, former scientist at the SRS of the CCLRC, in Daresbury, UK, for his help during the recording of the EXAFS data at SRS beam line 9.3 (project # AP 50049).

Publisher
Elsevier BV

Journal
Journal of Organometallic Chemistry

DOI
10.1016/j.jorganchem.2018.05.016

Additional Links
http://www.sciencedirect.com/science/article/pii/S0022328X18303863

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