Cationic molybdenum oxo alkylidenes stabilized by N-heterocyclic carbenes: from molecular systems to efficient supported metathesis catalysts |
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| Authors: | Janis V Musso Jordan De Jesus Silva Mathis J Benedikter Jonas Groos Wolfgang Frey Christophe Copret Michael R Buchmeiser |
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| Institution: | Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart Germany.; Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1–5, CH-8093 Zürich Switzerland.; Institute of Organic Chemistry, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart Germany ; German Institutes of Textile and Fiber Research (DITF) Denkendorf, Körschtalstr. 26, 73770 Denkendorf, Germany |
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| Abstract: | Cationic d0 group 6 olefin metathesis catalysts have been recently shown to display in most instances superior activity in comparison to their neutral congeners. Furthermore, their catalytic performance is greatly improved upon immobilization on silica. In this context, we have developed the new family of molecular cationic molybdenum oxo alkylidene complexes stabilized by N-heterocyclic carbenes of the general formula Mo(O)(CHCMe3)(IMes)(OR)X−]] (IMes = 1,3-dimesitylimidazol-2-ylidene; R = 1,3-dimesityl-C6H3, C6F5; X− = B(3,5-(CF3)2C6H3)4−, B(ArF)4, tetrakis(perfluoro-t-butoxy)aluminate (PFTA)). Immobilization of Mo(O)(CHCMe3)(IMes)(O-1,3-dimesityl-C6H3)+B(ArF)4−] on silica via surface organometallic chemistry yields an active alkene metathesis catalyst that shows the highest productivity towards terminal olefins amongst all existing molybdenum oxo alkylidene catalysts.The first cationic molybdenum oxo complexes were synthesized and immobilized on partially dehydroxylated silica. Vastly enhanced catalytic activity for terminal olefins was found compared to their neutral congeners. |
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