Mechanistic Insights into Ruthenium-Pincer-Catalyzed Amine-Assisted Homogeneous Hydrogenation of CO2 to Methanol,Journal of the American Chemical Society

当前位置： X-MOL 学术 › J. Am. Chem. Soc. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Mechanistic Insights into Ruthenium-Pincer-Catalyzed Amine-Assisted Homogeneous Hydrogenation of CO2 to Methanol
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2019-02-12 , DOI: 10.1021/jacs.8b12763
Sayan Kar ₁ , Raktim Sen ₁ , Jotheeswari Kothandaraman ₁ , Alain Goeppert ₁ , Ryan Chowdhury ₁ , Socrates B. Munoz ₁ , Ralf Haiges ₁ , G. K. Surya Prakash ₁

Affiliation

Amine-assisted homogeneous hydrogenation of CO2 to methanol is one of the most effective approaches to integrate CO2 capture with its subsequent conversion to CH3OH. The hydrogenation typically proceeds in two steps. In the first step the amine is formylated via an in situ formed alkylammonium formate salt (with consumption of 1 equiv of H2). In the second step the generated formamide is further hydrogenated with 2 more equiv of H2 to CH3OH while regenerating the amine. In the present study, we investigated the effect of molecular structure of the ruthenium pincer catalysts and the amines that are critical for a high methanol yield. Surprisingly, despite the high reactivity of several Ru pincer complexes [RuHClPNP R(CO)] (R = Ph/ i-Pr/Cy/ t-Bu) for both amine formylation and formamide hydrogenation, only catalyst Ru-Macho (R = Ph) provided a high methanol yield after both steps were performed simultaneously in one pot. Among various amines, only (di/poly)amines were effective in assisting Ru-Macho for methanol formation. A catalyst deactivation pathway was identified, involving the formation of ruthenium biscarbonyl monohydride cationic complexes [RuHPNP R(CO)2]+, whose structures were unambiguously characterized and whose reactivities were studied. These reactivities were found to be ligand-dependent, and a trend could be established. With Ru-Macho, the biscarbonyl species could be converted back to the active species through CO dissociation under the reaction conditions. The Ru-Macho biscarbonyl complex was therefore able to catalyze the hydrogenation of in situ formed formamides to methanol. Complex Ru-Macho-BH was also highly effective for this conversion and remained active even after 10 days of continuous reaction, achieving a maximum turnover number (TON) of 9900.

中文翻译：

钌-钳催化胺辅助 CO2 均相加氢制甲醇的机理研究

胺辅助将 CO2 均相氢化成甲醇是将 CO2 捕获与其随后转化为 CH3OH 相结合的最有效方法之一。氢化通常分两步进行。在第一步中，胺通过原位形成的甲酸烷基铵甲酰化（消耗 1 当量 H2）。在第二步中，生成的甲酰胺进一步用 2 当量的 H2 氢化成 CH3OH，同时再生胺。在本研究中，我们研究了钌钳状催化剂和对高甲醇产率至关重要的胺的分子结构的影响。令人惊讶的是，尽管几种 Ru 钳形配合物 [RuHClPNP R(CO)] (R = Ph/ i-Pr/Cy/ t-Bu) 对胺甲酰化和甲酰胺氢化具有高反应性，在一锅中同时进行两个步骤后，只有催化剂 Ru-Macho (R = Ph) 提供了高甲醇收率。在各种胺中，只有（二/多）胺可有效协助 Ru-Macho 形成甲醇。确定了催化剂失活途径，包括形成双羰基一氢化钌阳离子络合物 [RuHPNP R(CO)2]+，其结构已明确表征并研究其反应性。发现这些反应性是配体依赖性的，并且可以确定一种趋势。使用 Ru-Macho，双羰基物质可以在反应条件下通过 CO 解离转化回活性物质。因此，Ru-Macho 双羰基络合物能够催化原位形成的甲酰胺氢化成甲醇。

更新日期：2019-02-12

点击分享查看原文

点击收藏

阅读更多本刊新发论文本刊介绍/投稿指南