Catalyst Design for Alkene Epoxidation by Molecular Analogues of Heterogeneous Titanium-Silicalite Catalysts
| Autor: | Hugo Fouilloux, Albert Solé-Daura, Jorge J. Carbó, Lise-Marie Chamoreau, Anna Proust, Teng Zhang, Christophe M. Thomas, Geoffroy Guillemot, Carine Robert, Josep M. Poblet |
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| Přispěvatelé: | Universitat Rovira i Virgili, Institut Parisien de Chimie Moléculaire (IPCM), Chimie Moléculaire de Paris Centre (FR 2769), Institut de Chimie du CNRS (INC)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche de Chimie Paris (IRCP), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Ministère de la Culture (MC), Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL), Departament de Química Física i Inorgànica |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Allylic rearrangement
Molecular model 010405 organic chemistry chemistry.chemical_element General Chemistry Alkene epoxidation 010402 general chemistry 01 natural sciences Catalysis 0104 chemical sciences Silanol chemistry.chemical_compound chemistry Polymer chemistry [CHIM]Chemical Sciences Titanium |
| Zdroj: | ACS Catalysis ACS Catalysis, 2020, 10 (8), pp.4737--4750. ⟨10.1021/acscatal.9b05147⟩ |
| Popis: | International audience; The epoxidation of allylic alcohols with H2O2 catalyzed by the hybrid [α-B-SbW9O33(tBuSiO)3Ti(OiPr)]3\textendash (1) anion as a molecular model of heterogeneous Ti-silicalite TS-1 catalyst was analyzed by means of DFT to determine the main factors that control the catalytic process and, finally, to improve the value of the available catalysts. Our calculations revealed that unlike other alkenes, allylic alcohols can bind the Ti center after activation of the precatalyst via hydrolysis to give the corresponding Ti-alcoholate, which is the catalyst resting state. Next, the dissociative addition of hydrogen peroxide to Ti causes the cleavage of a Ti\textendash OSi junction to form a Ti(\eta2-OOH) moiety. The partial detachment of the Ti from the catalyst structure yields an intermediate with a flexible Ti center from which the Ti-OOH group can transfer an electrophilic oxygen to the alkene substrate in an inner-sphere fashion. The rate-determining process, which involves the heterolytic activation of H2O2 over the Ti(IV) and the electrophilic O-transfer, accounts for an overall free-energy barrier of 23.0 kcal mol\textendash 1 for 2-methyl-2-buten-1-ol, in line with the experimental value of 22.3. Conversely, the outer-sphere O-transfer\textemdash also accessible to nonfunctionalized alkenes\textemdash occurs through a more strained transition state that lays above in energy (by ∼4 kcal mol\textendash 1), giving a clue to explain the low yields reported experimentally for nonfunctionalized olefins. We also found that reducing the bulkiness of the substituents in the silanol functions of the catalyst has a positive influence on the catalytic activity, decreasing the overall free-energy barriers for the outer-sphere path. With this knowledge, we developed other catalytic species with tailored steric properties based on [SbW9O33(RSiOH)3]3\textendash structure (R =iPr and nPr), which were synthesized, characterized, and successfully applied to the catalytic epoxidation of unfunctionalized alkenes. Present results clearly show that the detailed knowledge of the reaction mechanisms, even for complex processes, is possible nowadays and that the acquired information allows designing catalysts with desired activities. |
| Databáze: | OpenAIRE |
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