Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry.
Type
ArticleKAUST Department
Chemical Science ProgramKAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Date
2019-11-05Permanent link to this record
http://hdl.handle.net/10754/660217
Metadata
Show full item recordAbstract
With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(≡Si-O-)Hf(=NMe)(η1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, <10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 °C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol·g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(≡Si-O-)Hf(η2π-MeNCH2)(η1-NMe2)(η1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(≡Si-O-)Hf(=NMe)(η1-NMe2)]. [(≡Si-O-)Hf(=NMe)(η1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(≡Si-O-)Hf(=NMe)(η1-NMe2)] is correlated to the catalytic performance.Citation
Aljuhani, M. A., Pelletier, J. D. A., & Basset, J.-M. (2019). Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry. Journal of Visualized Experiments, (152). doi:10.3791/59409Sponsors
The authors would like to express their thanks to the King Abdullah University of Science and Technology (KAUST) for financial and human support.Publisher
MyJove CorporationDOI
10.3791/59409Additional Links
https://www.jove.com/video/59409/imine-metathesis-silica-supported-catalysts-using-methodology-surfacehttps://www.jove.com/pdf/59409/imine-metathesis-silica-supported-catalysts-using-methodology-surface
Embedded External Content
ae974a485f413a2113503eed53cd6c53
10.3791/59409
Scopus Count
Except where otherwise noted, this item's license is described as Copyright © 2019 Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License