ISSN:
1434-1948
Schlagwort(e):
Mesoporous materials
;
MCM-41
;
MCM-48
;
Immobilisation
;
Solid-state NMR
;
Heterogeneous catalysis
;
Titanium
;
Titanocenes
;
Chemistry
;
General Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Titanium(IV)-grafted mesoporous silicas have been prepared by diffusion of an excess of the ansa-bridged titanocene [SiMe2(η5-C5H4)2]TiCl2 into the channels of hexagonal MCM-41 and cubic MCM-48 in dichloromethane or tetrahydrofuran at room temperature. The choice of solvent determines the course of the reaction and hence the activity of the resulting materials as catalysts in the catalytic epoxidation of cyclooctene with tert-butylhydroperoxide. Magic-angle spinning (MAS) NMR (13C, 29Si) spectroscopy was used to characterise the local environment of the surface-bound titanium active sites. When dichloromethane is used, the dominant species anchored to the surface are isolated ansa-bridged titanocene fragments. When THF is used, the [SiMe2(η5-C5H4)2] unit is lost with the concomitant formation of surface-bound TiIV species coordinated by THF molecules. These materials showed the best catalytic performance per Ti atom for the conversion of cyclooctene. All materials were further characterised by means of elemental analysis, powder X-ray diffraction (XRD), N2 adsorption and FTIR spectroscopy.
Zusätzliches Material:
7 Ill.
Materialart:
Digitale Medien
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