Modeling the Oxygen Vacancy at a Molecular Vanadium(III) Silica-Supported Catalyst

Autor: Albert Solé-Daura, Céline Paris, Sébastien Blanchard, Yanling Li, Teng Zhang, Sarah Hostachy, Josep M. Poblet, Jorge J. Carbó, Geoffroy Guillemot, Anna Proust
Přispěvatelé: 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), Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Edifices PolyMétalliques (E-POM), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Chimie Moléculaire de Paris Centre (FR 2769), De la Molécule aux Nanos-objets : Réactivité, Interactions et Spectroscopies (MONARIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Equipe de Recherche en Matériaux Moléculaires et Spectroscopies (ERMMES)
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Zdroj: Journal of the American Chemical Society
Journal of the American Chemical Society, American Chemical Society, 2018, 140 (44), pp.14903--14914. ⟨10.1021/jacs.8b09048⟩
ISSN: 0002-7863
1520-5126
Popis: Here we report on the use of a silanol-decorated polyoxotungstate, [SbW9O33(tBuSiOH)3]3\textendash (1), as a molecular support to describe the coordination of a vanadium atom at a single-site on silica surfaces. By reacting [V(Mes)3·thf] (Mes = 2,4,6-trimethylphenyl) with 1 in tetrahydrofuran, the vanadium(III) derivative [SbW9O33(tBuSiO)3V(thf)]3\textendash (2) was obtained. Compound 2 displays the paramagnetic behavior expected for a d2-VIII high spin complex (SQUID measurements) with a triplet electronic ground state (ca. 30 kcal·mol\textendash 1 more stable than the singlet, from DFT calculations). Compound 2 proves to be a reliable model for reduced isolated-vanadium atom dispersed on silica surfaces [(\equivSi\textemdash O)3VIII(OH2)], an intermediate that is often proposed in a Mars\textendash van Krevelen type mechanism for partial oxidation of light alcohols. Oxidation of 2 under air produced the oxo-derivative [SbW9O33(tBuSiO)3VO]3\textendash (3). In compound 2, the d2-electrons are localized in degenerated d(V) orbitals, whereas in the electronically analogous bireduced-[SbW9O33(tBuSiO)3VO]5\textendash, 3·(2e), one electron is localized on d(V) orbital and the second one is delocalized on the polyoxotungstic framework, leading to a unique case of a bireduced heteropolyanion derivative with completely decoupled d1-V(IV) and d1-W(V). Our body of experimental results (EPR, magnetic measurements, spectroelectrochemical studies, Raman spectroscopy) and theoretical studies highlights (i) the role of the apical ligand coordination, i.e., thf (σ-donor) vs oxo (π-donor), in destabilizing or stabilizing the d(V) orbitals relative to the d(W) orbitals, and (ii) a geometrical distortion of the O3VO entity that causes a splitting of the degenerated orbitals and the stabilization of one d(V) orbital in the bireduced compound 3·(2e).
Databáze: OpenAIRE
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