Stability of the first-generation Grubbs metathesis catalyst in a continuous flow reactor |
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| Affiliation: | 1. Tarragona, Spain;2. Riverside, CA, USA;1. Office of Scientific Research, Anhui Provincial Institute for Food and Drug Control, Hefei 230022, China;2. School of Pharmacy, Anhui University of Chinese Medicine, Hefei 230031, China;3. School of Materials and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China;4. School of Foreign Studies, Heifei University of Technology, Hefei 230009, China;1. School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via S. Agostino 1, 62032 Camerino, Italy;2. Dipartimento di Scienze per la Promozione della Salute e Materno-Infantile—Sezione di Farmacologia, Università di Palermo, 90127 Palermo, Italy;3. Department of Medical Biochemistry and Biophysics, Umeå University, SE-90187 Umeå, Sweden;4. Centro Interdipartimentale di Ricerca in Oncologia Clinica, Policlinico ‘P. Giaccone’, Università di Palermo, 90127 Palermo, Italy;5. Department of Biochemistry and Molecular Biology, Indiana University School of Medicine and Richard Roudebush VA Medical Center, Indianapolis, IN 46202, USA;1. Department of Natural and Synthetic Polymers, Faculty of Chemical Engineering, «Gheorghe Asachi» Technical University of Iasi, Prof. Dimitrie. Mangeron Street, 73, 700050 Iasi, Romania;2. CEA, LIST Saclay, Laboratoire Capteurs et Architectures Électroniques, 91191 Gif-sur-Yvette Cedex, France;1. School of Chemistry and Chemical Engineering, Xi''an Shiyou University, 18 Dian-zi-er Road, Xi''an, Shaanxi, PR China;2. Department of Chemistry, School of Science, Tianjin University, and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China;3. Frontier Institute of Science and Technology (FIST), State Key Laboratory for Mechanical Behavior of Materials and MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi''an Jiaotong University, Xi''an 710054, PR China;4. Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin 300071, China |
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| Abstract: | Ethylene pretreatment of the (PCy3)2Cl2Ru CHPh catalyst (1) prior to cross-metathesis of ethylene and cis-2-butene to form propylene in the continuous flow reactor produced a direct effect on catalyst deactivation. Similar cis-2-butene pretreatment of the same catalyst exhibited far less change in the catalyst activity. These results support the assumption that the ruthenium methylidene intermediate generated from ethylene and 1 is unstable and promotes catalyst loss while ruthenium alkylidenes, e.g. derived from 2-butene, exhibit significantly enhanced stability and sustained catalyst integrity. Continuous removal of products in the continuous flow reactor was important for separating the catalyst decay and the catalyst deactivation caused by a terminal olefin, in this case propylene.The amount of produced propylene during the 1 lifespan was determined in a series of tests using identical catalyst concentrations ([Ru] = 60 ppm) in pentadecane while varying the olefin pretreatment times from 0 to 420 min. The catalyst turnover numbers in the cross-metathesis experiments proved inversely proportional to the duration of ethylene treatment prior to the reaction. The activity of 1 pre-exposed to ethylene closely matched with the activity of the catalyst that decayed in the reaction mixture containing ethylene and cis-2-butene for the same period of time. A significant contribution of the Ru-methylidene decay to the activity losses in metathesis reactions was demonstrated directly in the cross-metathesis reaction environment. The catalyst proved to be less sensitive to cis-2-butene pretreatment and showed turnover numbers for subsequent cross-metathesis essentially similar to the reference cross-metathesis test. |
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