title: 17O NMR gives unprecedented insights into the structure of supported catalysts and their interaction with the silica carrier.
abstract: Flame silica was surface-labeled with (17)O, through isotopic enrichment of both siloxanes and silanols. After heat treatment at 200 and 700 °C under vacuum, the resulting partially dehydroxylated silica materials were investigated by high-field solid-state (1)H and (17)O NMR. More specifically, MQ MAS and HMQC sequences were used to probe the (17)O local environment. In a further step, these (17)O-tagged supports were used for the preparation of supported catalysts by reaction with perhydrocarbyl transition metal derivatives (zirconium tetraalkyl, tantalum trisalkyl-alkylidene, and tungsten trisalkyl-alkylidyne complexes). Detailed (17)O 1D and 2D MQ and HMQC MAS NMR studies demonstrate that signals in the Si-OH, Si-O-Si, and Si-O-metal regions are highly sensitive to local structural modifications, thanks to (17)O 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.
authors.affiliation: Laboratoire de Chimie Organométallique de Surface, Villeurbanne, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Merle
authors.forename: Julien
authors.initials: J
authors.lastname: Trébosc
authors.forename: Anne
authors.initials: A
authors.lastname: Baudouin
authors.forename: Iker Del
authors.initials: ID
authors.lastname: Rosal
authors.forename: Laurent
authors.initials: L
authors.lastname: Maron
authors.forename: Kai
authors.initials: K
authors.lastname: Szeto
authors.forename: Marie
authors.initials: M
authors.lastname: Genelot
authors.forename: André
authors.initials: A
authors.lastname: Mortreux
authors.forename: Mostafa
authors.initials: M
authors.lastname: Taoufik
authors.forename: Laurent
authors.initials: L
authors.lastname: Delevoye
authors.forename: Régis M
authors.initials: RM
authors.lastname: Gauvin