17O NMR Gives Unprecedented Insights into the Structure of Supported Catalysts and Their Interaction with the Silica Carrier

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• 作者：Nicolas Merle ; Julien Tr茅bosc ; Anne Baudouin ; Iker Del Rosal ; Laurent Maron ; Kai Szeto ; Marie Genelot ; Andr茅 Mortreux ; Mostafa Taoufik ; Laurent Delevoye ; R茅gis M. Gauvin
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：June 6, 2012
• 年：2012
• 卷：134
• 期：22
• 页码：9263-9275
• 全文大小：667K
• 年卷期：v.134,no.22(June 6, 2012)
• ISSN：1520-5126

文摘

Flame silica was surface-labeled with ¹⁷O, through isotopic enrichment of both siloxanes and silanols. After heat treatment at 200 and 700 掳C under vacuum, the resulting partially dehydroxylated silica materials were investigated by high-field solid-state ¹H and ¹⁷O NMR. More specifically, MQ MAS and HMQC sequences were used to probe the ¹⁷O local environment. In a further step, these ¹⁷O-tagged supports were used for the preparation of supported catalysts by reaction with perhydrocarbyl transition metal derivatives (zirconium tetraalkyl, tantalum trisalkyl鈥揳lkylidene, and tungsten trisalkyl鈥揳lkylidyne complexes). Detailed ¹⁷O 1D and 2D MQ and HMQC MAS NMR studies demonstrate that signals in the Si鈥?b>OH, Si鈥?b>O鈥揝i, and Si鈥?b>O鈥搈etal regions are highly sensitive to local structural modifications, thanks to ¹⁷O wide chemical shift and quadrupolar constant ranges. Experimental results were supported by DFT calculations. From the selective surface labeling, unprecedented information on interactions between supported catalysts and their inorganic carrier has been extracted.