Reaction mechanism of the reductive elimination in the catalytic carbonylation of methanol. A density functional study |
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| Affiliation: | 1. Den – Service d’Études du Comportement des Radionucléides (SECR), CEA, Université Paris-Saclay, F–91191 Gif-sur-Yvette, France;2. Den – Service d’Études Analytiques et de Réactivité des Surfaces (SEARS), CEA, Université Paris-Saclay, F–91191 Gif-sur-Yvette, France;1. Department of Veterinary Pathobiology, Texas A&M University, College Station, TX, USA;2. Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA;3. Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, USA;4. Department of Small Animal Clinical Sciences, Texas A&M University, College Station, TX, USA;1. The college of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China;2. China railway siyuan survey and design group co.ltd. Wuhan Hubei 430063, China;1. Department of Chemistry, University College London, 20 Gordon Street, London, WC1H OAJ, UK;2. Department of Chemistry, P.O. Box 305070, University of North Texas, Denton, TX 76203-5070, USA;3. Geological Survey Department of Cyprus, Ministry of Agriculture, Rural Development and Environment, Lefkonos 1, Lefkosia 1415, Cyprus |
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| Abstract: | Reductive elimination, the final step of the Monsanto and Cativa processes, has been studied using the density functional theory with the hybrid B3LYP exchange and correlation functional. To our knowledge, this is the first systematic computational study of the reductive elimination for which even the experimental studies are rare. We have studied different isomers of the anionic dicarbonyls [Rh(CO)2(COCH3)I3]− (1) and [Ir(CO)2(COCH3)I3]− (2). Several possible reaction routes for the elimination of CH3COI from 1 and 2 have been explored. In addition, different isomers of the neutral tricarbonyl [Ir(CO)3(COCH3)I2] (3) and possible reaction paths connected to 3 have been studied. Our results show mer,trans-1 to be the dominant intermediate in the rhodium system although its transformation to fac,cis-1 and the elimination from this seems to be the most likely reaction pathway. In the anionic iridium system, the dominating intermediate is proposed to be fac,cis-2. In the neutral iridium system, mer,cis-3 is proposed to be the dominant intermediate. While inspecting the iridium system as a whole, one could propose a transformation from anionic dicarbonyl to neutral tricarbonyl that would enhance the total rate of the reductive elimination. This observation is similar to that already verified in the 1,1-insertion in the Cativa process. In general, the geometrical arrangement of the different ligands has a large effect on the catalytic activity of the different possible intermediates of these processes. |
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