Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Am Chem Soc. 2012 Mar 21;134(11):5180-6. doi: 10.1021/ja2105834. Epub 2012 Mar 7.
The chemical conversion of CO(2) has been studied by numerous experimental groups. Particularly the use of rhenium tricarbonyl-based molecular catalysts has attracted interest owing to their ability to absorb light, store redox equivalents, and convert CO(2) into higher-energy products. The mechanism by which these catalysts mediate reduction, particularly to CO and HCOO(-), is poorly understood, and studies aimed at elucidating the reaction pathway have likely been hindered by the large number of species present in solution. Herein the mechanism for carbon monoxide production using rhenium tricarbonyl catalysts has been investigated using density functional theory. The investigation presented proceeds from the experimental work of Meyer's group (J. Chem. Soc., Chem. Commun.1985, 1414-1416) in DMSO and Fujita's group (J. Am. Chem. Soc.2003, 125, 11976-11987) in dry DMF. The latter work with a simplified reaction mixture, one that removes the photo-induced reduction step with a sacrificial donor, is used for validation of the proposed mechanism, which involves formation of a rhenium carboxylate dimer, Re(dmb)(CO)(3)(OCO), where dmb = 4,4'-dimethyl-2,2'-bipyridine. CO(2) insertion into this species, and subsequent rearrangement, is proposed to yield CO and the carbonate-bridged Re(dmb)(CO)(3)(OCO(2)). Structures and energies for the proposed reaction path are presented and compared to previously published experimental observations.
CO(2) 的化学转化已被众多实验小组研究。特别地，由于铼三羰基基分子催化剂具有吸收光、储存氧化还原当量以及将 CO(2) 转化为高能产物的能力，因此它们的使用引起了人们的兴趣。这些催化剂介导还原的机制，特别是还原为 CO 和 HCOO(-)，理解得很差，并且旨在阐明反应途径的研究可能由于溶液中存在的大量物种而受到阻碍。在此，使用密度泛函理论研究了使用铼三羰基催化剂生产一氧化碳的机理。本研究源自 Meyer 小组（J. Chem. Soc.，Chem. Commun.1985，1414-1416）在 DMSO 和 Fujita 小组（J. Am. Chem. Soc.2003，125，11976-11987）在干燥 DMF 中的实验工作。后者使用简化的反应混合物，即通过牺牲供体去除光诱导还原步骤，用于验证所提出的机理，该机理涉及形成铼羧酸盐二聚体Re(dmb)(CO)(3)(OCO)，其中 dmb = 4,4'-二甲基-2,2'-联吡啶。该物种中 CO(2) 的插入以及随后的重排被提议生成 CO 和碳酸盐桥接的Re(dmb)(CO)(3)(OCO(2))。提出了反应途径的结构和能量，并与以前发表的实验观察结果进行了比较。
