Accessing Realistic Models for the WO3–SiO2 Industrial Catalyst through the Design of Organometallic Precursors

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• 作者：Y. Bouhoute ; D. Grekov ; K. C. Szeto ; N. Merle ; A. De Mallmann ; F. Lefebvre ; G. Raffa ; I. Del Rosal ; L. Maron ; R. M. Gauvin ; L. Delevoye ; M. Taoufik
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：January 4, 2016
• 年：2016
• 卷：6
• 期：1
• 页码：1-18
• 全文大小：982K
• ISSN：2155-5435

文摘

In order to access realistic models to the industrial olefin metathesis catalyst WO₃/SiO₂, which is the bigrafted tungsten oxo alkylidene species [(≡SiO)₂WO(═CHR)], we targeted the parent bis-alkyl oxo derivative [(≡SiO)₂WOR₂] prone to carbene formation. Thus, grafting of [WO(CH₂EMe₃)₃Cl] (E = C, 1-Np; E = Si, 1-Ns) onto silica dehydroxylated at 200 °C was performed. While 1-Np affords the monopodal species [(≡SiO)WO(CH₂CMe₃)₃] (2-Np), the neosilyl derivative 1-Ns reacts to yield the well-defined bipodal species [(≡SiO)₂WO(CH₂SiMe₃)₂] (2-Ns), via consecutive HCl and SiMe₄ release. This was demonstrated by mass balance analysis, elemental analysis, IR, advanced solid-state NMR (1D and 2D ¹H, ¹³C, ²⁹Si, and ¹⁷O), and EXAFS. Furthermore, DFT calculations allowed understanding and rationalizing the experimental results regarding grafting selectivity. The material 2-Ns proved to lead to the most stable and efficient supported tungsten oxo catalyst for propene metathesis under dynamic conditions at 80 °C.