Alkyne Metathesis with Silica‐Supported and Molecular Catalysts at Parts‐per‐Million Loadings |
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| Authors: | Deven P Estes Martin Casey Alexey Fedorov Matthias Tamm Christophe Copéret |
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| Affiliation: | 1. Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich, Switzerland;2. Institut für Anorganische und Analytische Chemie, Technische Universit?t Braunschweig, Braunschweig, Germany |
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| Abstract: | Improvement of the activity, stability, and chemoselectivity of alkyne‐metathesis catalysts is necessary before this promising methodology can become a routine method to construct C≡C triple bonds. Herein, we show that grafting of the known molecular catalyst MesC≡Mo(OtBuF6)3] ( 1 , Mes=2,4,6‐trimethylphenyl, OtBuF6=hexafluoro‐tert‐butoxy) onto partially dehydroxylated silica gave a well‐defined silica‐supported active alkyne‐metathesis catalyst (≡SiO)Mo(≡CMes)(OtBuF6)2] ( 1 /SiO2‐700). Both 1 and 1 /SiO2‐700 showed very high activity, selectivity, and stability in the self‐metathesis of a variety of carefully purified alkynes, even at parts‐per‐million catalyst loadings. Remarkably, the lower turnover frequencies observed for 1 /SiO2‐700 by comparison to 1 do not prevent the achievement of high turnover numbers. We attribute the lower reactivity of 1 /SiO2‐700 to the rigidity of the surface Mo species owing to the strong interaction of the metal site with the silica surface. |
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| Keywords: | alkynes metathesis molybdenum NMR spectroscopy supported catalysts |
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