TY - JOUR
T1 - Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N-Donor SBA15 Surface Ligands
T2 - A Solid-State NMR and DFT Study
AU - Bendjeriou-Sedjerari, Anissa
AU - Sofack-Kreutzer, Julien
AU - Minenkov, Yury
AU - Abou-Hamad, Edy
AU - Hamzaoui, Bilel
AU - Werghi, Baraa
AU - Anjum, Dalaver H.
AU - Cavallo, Luigi
AU - Huang, Kuo Wei
AU - Basset, Jean Marie
N1 - Funding Information:
This work received support from the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. CRG_R2_13_BASS_KAUST_1.
Publisher Copyright:
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2016/9/5
Y1 - 2016/9/5
N2 - Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡CtBu)(CH2tBu)3with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2)], leads to [(≡SiNH2−)(≡SiO−)W(≡CHtBu)(CH2tBu)2] and [(≡SiNH2−)(≡SiO−)W(=CHtBu)2(CH2tBu). 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.
AB - Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡CtBu)(CH2tBu)3with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2)], leads to [(≡SiNH2−)(≡SiO−)W(≡CHtBu)(CH2tBu)2] and [(≡SiNH2−)(≡SiO−)W(=CHtBu)2(CH2tBu). 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.
KW - chelating ligands
KW - SBA15 silica
KW - surface organometallic chemistry
KW - tautomerization
KW - α-H exchange
UR - http://www.scopus.com/inward/record.url?scp=84981492646&partnerID=8YFLogxK
U2 - 10.1002/anie.201605934
DO - 10.1002/anie.201605934
M3 - Article
AN - SCOPUS:84981492646
SN - 1433-7851
VL - 55
SP - 11162
EP - 11166
JO - Angewandte Chemie - International Edition
JF - Angewandte Chemie - International Edition
IS - 37
ER -