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- Title
Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N-Donor SBA15 Surface Ligands: A Solid-State NMR and DFT Study.
- Authors
Bendjeriou-Sedjerari, Anissa; Sofack-Kreutzer, Julien; Minenkov, Yury; Abou-Hamad, Edy; Hamzaoui, Bilel; Werghi, Baraa; Anjum, Dalaver H.; Cavallo, Luigi; Huang, Kuo-Wei; Basset, Jean-Marie
- Abstract
Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡C tBu)(CH2 tBu)3 with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2)], leads to [(≡SiNH2−)(≡SiO−)W(≡CH tBu)(CH2 tBu)2] and [(≡SiNH2−)(≡SiO−)W(=CH tBu)2(CH2 tBu). Variable temperature, 1H-1H 2D double-quantum, 1H-13C HETCOR, and HETCOR with spin diffusion solid-state NMR spectroscopy demonstrate tautomerization between the alkyl alkylidyne and the bis(alkylidene) on the SBA15 surface. Such equilibrium is possible through the coordination of W to the surface [(≡Si−OH)(≡Si−NH2)] groups, which act as a [N,O] pincer ligand. DFT calculations provide a rationalization for the surface-complex tautomerization and support the experimental results. This direct observation of such a process shows the strong similarity between molecular mechanisms in homogeneous and heterogeneous catalysis. In propane metathesis (at 150 °C), the tungsten bis(carbene) tautomer is favorable, with a turnover number (TON) of 262. It is the highest TON among all the tungsten alkyl-supported catalysts.
- Subjects
TRANSITION metal compounds spectra; TUNGSTEN compounds; LIGAND exchange reactions; TAUTOMERISM; STRUCTURAL isomerism; TUNGSTEN compounds synthesis; MOLECULAR structure of tungsten compounds
- Publication
Angewandte Chemie International Edition, 2016, Vol 55, Issue 37, p11162
- ISSN
1433-7851
- Publication type
Article
- DOI
10.1002/anie.201605934