Geng Lina, Zhang Mingchao, Zhang Zhiqiang, Li Yan
School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Road 185, Anshan 114051, China.
Dalton Trans. 2023 Oct 3;52(38):13653-13661. doi: 10.1039/d3dt01912h.
To understand the mechanism of the dehydrogenation of methanol to CO and H catalyzed by a ruthenium pincer complex, a density functional theory (DFT) study has been conducted on two different cycles which differ in the substances entering the cycle (methanol (cycle 1) methoxymethanol (cycle 2)). Our calculated results show that both cycles consist of three stages: dehydrogenation of alcohol to aldehyde (stage I); hydrogen formation (stage II); and decarbonylation with the regeneration of the catalyst (stage III). The energy barriers of the rate-determining steps for cycles 1 and 2 are 49.6 and 28.5 kcal mol, respectively. Thus cycle 2 is more energetically feasible. For stage III of cycle 2, our results did not support the mechanism proposed in the experiment (CO release occurs prior to decarbonylation). Instead, we suggested and examined an alternative pathway, that is, decarbonylation occurs prior to CO release. The mechanistic insights gained in the present paper could be beneficial for further designing of these kinds of reactions.
为了解钌钳形配合物催化甲醇脱氢生成一氧化碳和氢气的机理，我们对两种不同的循环进行了密度泛函理论（DFT）研究，这两种循环在进入循环的物质（甲醇（循环1）和甲氧基甲醇（循环2））上有所不同。我们的计算结果表明，两个循环均由三个阶段组成：醇脱氢生成醛（阶段I）；生成氢气（阶段II）；以及催化剂再生的脱羰反应（阶段III）。循环1和循环2的速率决定步骤的能垒分别为49.6和28.5千卡/摩尔。因此，循环2在能量上更可行。对于循环2的阶段III，我们的结果不支持实验中提出的机理（脱羰反应之前先释放一氧化碳）。相反，我们提出并研究了另一种途径，即脱羰反应在释放一氧化碳之前发生。本文获得的机理见解可能有助于进一步设计这类反应。
