Neutral and Cationic Molybdenum Imido Alkylidene N‐Heterocyclic Carbene Complexes: Reactivity in Selected Olefin Metathesis Reactions and Immobilization on Silica |
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| Authors: | Suman Sen Roman Schowner Dominik A. Imbrich Dr. Wolfgang Frey Prof. Michael Hunger Prof. Michael R. Buchmeiser |
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| Affiliation: | 1. Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring?55, 70569 Stuttgart (Germany);2. Institute of Organic Chemistry, University of Stuttgart, Pfaffenwaldring?55, 70569 Stuttgart (Germany);3. Institute of Chemical Technology, University of Stuttgart, Pfaffenwaldring?55, 70569 (Germany);4. Institute of Textile Chemistry and Chemical Fibers, K?rschtalstr.?26, 73770 Denkendorf (Germany) |
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| Abstract: | The synthesis and single‐crystal X‐ray structures of the novel molybdenum imido alkylidene N‐heterocyclic carbene complexes [Mo(N‐2,6‐Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf)2] ( 3 ), [Mo(N‐2,6‐Me2C6H3)(IMes)(CHCMe2Ph)(OTf)2] ( 4 ), [Mo(N‐2,6‐Me2C6H3)(IMesH2)(CHCMe2Ph)(OTf){OCH(CF3)2}] ( 5 ), [Mo(N‐2,6‐Me2C6H3)(CH3CN)(IMesH2)(CHCMe2Ph)(OTf)]+ BArF? ( 6 ), [Mo(N‐2,6‐Cl2C6H3)(IMesH2)(CHCMe3)(OTf)2] ( 7 ) and [Mo(N‐2,6‐Cl2C6H3)(IMes)(CHCMe3)(OTf)2] ( 8 ) are reported (IMesH2=1,3‐dimesitylimidazolidin‐2‐ylidene, IMes=1,3‐dimesitylimidazolin‐2‐ylidene, BArF?=tetrakis‐[3,5‐bis(trifluoromethyl)phenyl] borate, OTf=CF3SO3?). Also, silica‐immobilized versions I1 and I2 were prepared. Catalysts 3 – 8 , I1 and I2 were used in homo‐, cross‐, and ring‐closing metathesis (RCM) reactions and in the cyclopolymerization of α,ω‐diynes. In the RCM of α,ω‐dienes, in the homometathesis of 1‐alkenes, and in the ethenolysis of cyclooctene, turnover numbers (TONs) up to 100 000, 210 000 and 30 000, respectively, were achieved. With I1 and I2 , virtually Mo‐free products were obtained (<3 ppm Mo). With 1,6‐hepta‐ and 1,7‐octadiynes, catalysts 3 , 4 , and 5 allowed for the regioselective cyclopolymerization of 4,4‐bis(ethoxycarbonyl)‐1,6‐heptadiyne, 4,4‐bis(hydroxymethyl)‐1,6‐heptadiyne, 4,4‐bis[(3,5‐diethoxybenzoyloxy)methyl]‐1,6‐heptadiyne, 4,4,5,5‐tetrakis(ethoxycarbonyl)‐1,7‐octadiyne, and 1,6‐heptadiyne‐4‐carboxylic acid, underlining the high functional‐group tolerance of these novel Group 6 metal alkylidenes. |
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| Keywords: | alkylidene immobilization molybdenum N‐heterocyclic carbenes olefin metathesis |
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