Olefin Hydrosilylation Catalyzed by a Bis-N-Heterocyclic Carbene Rhodium Complex. A Density Functional Theory Study

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• 作者：Yin Wu ; Virve A. Karttunen ; Shane Parker ; Alexander Genest ; Notker R枚sch
• 刊名：Organometallics
• 出版年：2013
• 出版时间：April 22, 2013
• 年：2013
• 卷：32
• 期：8
• 页码：2363-2372
• 全文大小：471K
• 年卷期：v.32,no.8(April 22, 2013)
• ISSN：1520-6041

文摘

Using a density functional theory method, we explored four reaction mechanisms of hydrosilylation of silane and ethylene as model substrates, catalyzed by a Rh(I) complex with a bidendate ethylene-bridged bis-N-heterocyclic carbene ligand. We examined in detail the energy profiles of the Glaser鈥揟illey, Chalk鈥揌arrod, and modified Chalk鈥揌arrod mechanisms, as well as of 蟽-bond metathesis. The Chalk鈥揌arrod mechanism and 蟽-bond metathesis were determined most favorable, with the calculated highest relative activation enthalpies of 9.3 and 8.6 kcal mol^鈥?, respectively. We also studied a potential side reaction in the 蟽-bond metathesis that leads to the formation of ethane; its rate-limiting activation enthalpy is sufficiently high, 20.9 kcal mol^鈥? (14.6 kcal mol^鈥? higher than the competing barrier on the main pathway), not to be competitive. The feasibility of crucial reaction steps, C鈥揌 and C鈥揝i bond formation, was found to correlate with the ease of conformational changes of the bis-N-heterocyclic carbene ligand, thus providing a hint at optimum ligand design.