title: Silica-surface reorganization during organotin grafting evidenced by ¹¹⁹Sn DNP SENS: a tandem reaction of gem-silanols and strained siloxane bridges.
abstract: Grafting reactive molecular complexes on dehydroxylated amorphous silica is a strategy to develop "single-site" heterogeneous catalysts. In general, only the reactivity of isolated silanols is invoked for silica dehydroxylated at 700 °C ([SiO(2-700)]), though ca. 10% of the surface silanols are in fact geminal Q2-silanols. Here we report the reaction of allyltributylstannane with [SiO(2-700)] and find that the geminal Q2-silanols react to form products that would formally arise from vicinal Q3-silanols that are not present on [SiO(2-700)], indicating that a surface rearrangement occurs. The reorganization of the silica surface is unique to silica dehydroxylated at 700 °C or above. The findings were identified using Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy (DNP SENS) combined with DFT calculations.
authors.affiliation: Department of Chemistry and Applied Biosciences, Vladimir Prelog Weg 2 ETH Zürich, CH-8093 Zürich, Switzerland. ccoperet@inorg.chem.ethz.ch.
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Conley
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Rossini
authors.forename: Aleix
authors.initials: A
authors.lastname: Comas-Vives
authors.forename: Maxence
authors.initials: M
authors.lastname: Valla
authors.forename: Gilles
authors.initials: G
authors.lastname: Casano
authors.forename: Olivier
authors.initials: O
authors.lastname: Ouari
authors.forename: Paul
authors.initials: P
authors.lastname: Tordo
authors.forename: Anne
authors.initials: A
authors.lastname: Lesage
authors.forename: Lyndon
authors.initials: L
authors.lastname: Emsley
authors.forename: Christophe
authors.initials: C
authors.lastname: Copéret