Lu Qianqian, Song Jinshuai, Zhang Minyi, Wei Jing, Li Chunsen
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China.
Dalton Trans. 2018 Feb 13;47(7):2460-2469. doi: 10.1039/c7dt04447j.
The mechanism of the ruthenium carboxylate-catalyzed hydrogenation of carboxylic acids was investigated by using density functional theory (DFT) calculations. The novel mechanism including two hydrogenation cycles was proposed for this reaction. The first cycle is the hydrogenation of the carboxylic acid to an aldehyde, while the second cycle is the hydrogenation of the aldehyde to an alcohol. These two catalytic cycles share similar elementary steps, including H heterolysis, hydride migration of the carboxylic acid or aldehyde, and catalyst regeneration. In this hydrogenation mechanism, the carboxylic acid is not only a reactant, but also an important proton source. Furthermore, the noncovalent interaction (e.g. hydrogen bonding interaction) between the ligand and carboxylic acid substrate could promote the hydrogenation of the carboxylic acid through stabilizing the transition state of the most energy-demanding step (i.e., hydride migration in the first catalytic cycle). Besides, the strong electron-donating ability of the dppb ligand could also facilitate the hydride migration.
通过密度泛函理论（DFT）计算研究了羧酸钌催化羧酸加氢的机理。针对该反应提出了包括两个加氢循环的新机理。第一个循环是羧酸加氢生成醛，而第二个循环是醛加氢生成醇。这两个催化循环具有相似的基本步骤，包括氢的异裂、羧酸或醛的氢化物迁移以及催化剂再生。在这种加氢机理中，羧酸不仅是反应物，还是重要的质子源。此外，配体与羧酸底物之间的非共价相互作用（如氢键相互作用）可通过稳定能量需求最高步骤（即第一个催化循环中的氢化物迁移）的过渡态来促进羧酸的加氢。此外，dppb配体的强给电子能力也有助于氢化物迁移。
