Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, 8093, Zürich, Switzerland.
Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106, Braunschweig, Germany.
Angew Chem Int Ed Engl. 2016 Nov 2;55(45):13960-13964. doi: 10.1002/anie.201605129. Epub 2016 Aug 3.
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(OtBu ) ] (1, Mes=2,4,6-trimethylphenyl, OtBu =hexafluoro-tert-butoxy) onto partially dehydroxylated silica gave a well-defined silica-supported active alkyne-metathesis catalyst [(≡SiO)Mo(≡CMes)(OtBu ) ] (1/SiO ). Both 1 and 1/SiO 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/SiO by comparison to 1 do not prevent the achievement of high turnover numbers. We attribute the lower reactivity of 1/SiO to the rigidity of the surface Mo species owing to the strong interaction of the metal site with the silica surface.
在这种很有前景的方法成为构建 C≡C 三键的常规方法之前，有必要提高炔烃复分解催化剂的活性、稳定性和化学选择性。在此，我们证明，将已知的分子催化剂[MesC≡Mo(OtBu)]（1，Mes=2,4,6-三甲基苯基，OtBu=六氟叔丁氧基）接枝到部分脱羟基的硅胶上得到了一种明确的负载于硅胶上的活性炔烃复分解催化剂[(≡SiO)Mo(≡CMes)(OtBu)]（1/SiO）。在各种精心纯化的炔烃的自复分解反应中，无论是在ppm 级别的催化剂负载量下，1 和 1/SiO 均表现出非常高的活性、选择性和稳定性。值得注意的是，与 1 相比，1/SiO 的较低的周转率频率并不会阻止达到高的周转数。我们将 1/SiO 的较低反应性归因于由于金属位点与硅胶表面的强相互作用，表面 Mo 物种的刚性。
