Solid‐State NMR Characterization of Wilkinson’s Catalyst Immobilized in Mesoporous SBA‐3 Silica |
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Authors: | Anna Grünberg Dr. Xu Yeping Dr. Hergen Breitzke Dr. Gerd Buntkowsky Prof. |
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Affiliation: | Eduard‐Zintl‐Institut für Anorganische und Physikalische Chemie, Technische Universit?t Darmstadt, Petersenstr. 20, 64287 Darmstadt (Germany), Fax: (+49)?6151‐164347 |
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Abstract: | The Wilkinson’s catalyst [RhCl(PPh3)3] has been immobilized inside the pores of amine functionalized mesoporous silica material SBA‐3 and The structure of the modified silica surface and the immobilized rhodium complex was determined by a combination of different solid‐state NMR methods. The successful modification of the silica surface was confirmed by 29Si CP‐MAS NMR experiments. The presence of the Tn peaks confirms the successful functionalization of the support and shows the way of binding the organic groups to the surface of the mesopores. 31P‐31P J‐resolved 2D MAS NMR experiments were conducted in order to characterize the binding of the immobilized catalyst to the amine groups of the linkers attached to the silica surface. The pure catalyst exhibits a considerable 31P‐31P J‐coupling, well resolvable in 2D MAS NMR experiments. This J‐coupling was utilized to determine the binding mode of the catalyst to the linkers on the silica surface and the number of triphenylphosphine ligands that are replaced by coordination bonds to the amine groups. From the absence of any resolvable 31P‐31P J‐coupling in off‐magic‐angle‐spinning experiments, as well as slow‐spinning MAS experiments, it is concluded, that two triphenylphosphine ligands are replaced and that the catalyst is bonded to the silica surface through two linker molecules. |
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Keywords: | heterogeneous catalysis NMR spectroscopy phosphorus Wilkinson’ s catalyst |
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