Concerted or Stepwise Hydrogen Transfer in the Transfer Hydrogenation of Acetophenone Catalyzed by Ruthenium鈥揂cetamido Complex: A Theoretical Mechanistic Investigation
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- 作者：Xiaojia Guo ; Yanhui Tang ; Xin Zhang ; Ming Lei
- 刊名：Journal of Physical Chemistry A
- 出版年：2011
- 出版时间：November 10, 2011
- 年：2011
- 卷：115
- 期：44
- 页码：12321-12330
- 全文大小：1106K
- 年卷期：v.115,no.44(November 10, 2011)
- ISSN：1520-5215
文摘
In this paper, the mechanism of transfer hydrogenation of acetophenone catalyzed by ruthenium鈥揳cetamido complex was studied using density function theory (DFT) method. The catalytic cycle of transfer hydrogenation consists of hydrogen transfer (HT) step and dehydrogenation (DH) step of isopropanol (IPA). Inner sphere mechanism (paths 1 and 7) and outer sphere mechanism (paths 2鈥?) in HT step are fully investigated. Calculated results indicate that DH step of IPA (from i1 to i2) is the rate-determining step in the whole catalytic cycle, which has a potential energy barrier of 16.2 kcal/mol. On the other hand, the maximum potential energy barriers of paths 1鈥? in the HT step are 5.9, 12.7, 24.4, 16.8, 23.7, 7.2, and 6.1 kcal/mol, respectively. The inner sphere pathways (paths 1 and 7) are favorable hydrogen transfer modes compared with outer sphere pathways, and the proton transferred to the oxygen atom of acetophenone comes from the hydroxyl group but not from amino group of acetamido ligand. Those theoretical results are in agreement with experimental report. However, in view of this DFT study in the inner sphere mechanism of HT step, hydride transfer and proton transfer are concerted and asynchronous hydrogen transfer but not a stepwise one, and hydride transfer precedes proton transfer in this case.