Alkene Epoxidation Catalysts [Ru(pdc)(tpy)] and [Ru(pdc)(pybox)] Revisited: Revealing a Unique RuIV鈺怬 Structure from a Dimethyl Sulfoxide Coordinating Complex

详细信息    查看全文

• 作者：Ying Wang ; Lele Duan ; Lei Wang ; Hong Chen ; Junliang Sun ; Licheng Sun ; M氓rten S. G. Ahlquist
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：5
• 期：7
• 页码：3966-3972
• 全文大小：437K
• ISSN：2155-5435

文摘

The X-ray crystal structure of a dimethyl sulfoxide (DMSO) coordinating complex [Ru^II(魏²-pdc)(tpy)(DMSO)] (H₂pdc = 2,6-pyridyl dicarboxylic acid and tpy = 2,2鈥?6鈥?2鈥?terpyridine) led to the discovery of a unique Ru^IV鈺怬 configuration for the Ru-pybox (pybox = pyridine-bis(oxazoline) ligands) epoxidation catalyst by theoretical calculations. On the basis of this structure, a detailed theoretical study was conducted on the alkene epoxidation reaction using ruthenium-based epoxidation catalysts. It was found that the process of H₂O₂ coordination proceeded via an associative path in which one carboxylate detached. The following H₂O-elimination step was found to be facilitated by the detached carboxylate group. The resulting Ru^IV鈺怬 rearranges to the species trans-2a-oxo, in which one carboxylate group is situated over the tpy ring; the trans-2a-oxo was found to have the lowest activation free energies toward alkene epoxidation. These results demonstrated the importance of the hemilabile properties of the pdc^{2鈥?/sup> ligand for the Ru-pdc alkene epoxidation catalysts.}