title: Tungsten(VI) Carbyne/Bis(carbene) Tautomerization Enabled by N-Donor SBA15 Surface Ligands: A Solid-State NMR and DFT Study.
abstract: Designing supported well-defined bis(carbene) complexes remains a key challenge in heterogeneous catalysis. The reaction of W(≡CtBu)(CH2 tBu)3 with amine-modified mesoporous SBA15 silica, which has vicinal silanol/silylamine pairs [(≡SiOH)(≡SiNH2 )], leads to [(≡SiNH2 -)(≡SiO-)W(≡CHtBu)(CH2 tBu)2 ] and [(≡SiNH2 -)(≡SiO-)W(=CHtBu)2 (CH2 tBu). Variable temperature, (1) H-(1) H 2D double-quantum, (1) H-(13) C 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.
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Anissa
authors: A
authors: Bendjeriou-Sedjerari
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Julien
authors: J
authors: Sofack-Kreutzer
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Yury
authors: Y
authors: Minenkov
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Edy
authors: E
authors: Abou-Hamad
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Bilel
authors: B
authors: Hamzaoui
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Baraa
authors: B
authors: Werghi
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Dalaver H
authors: DH
authors: Anjum
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Luigi
authors: L
authors: Cavallo
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia.
authors: Kuo-Wei
authors: KW
authors: Huang
authors: King Abdullah University of Science and Technology (KAUST), Kaust Catalysis Center (KCC), Thuwal, 23955-6900, Saudi Arabia. jeanmarie.basset@kaust.edu.sa.
authors: Jean-Marie
authors: JM
authors: Basset
keywords: SBA15 silica; chelating ligands; surface organometallic chemistry; tautomerization; α-H exchange