Department of Chemistry, Faculty of Science, Central Tehran Branch, Islamic Azad University, Shahrak Gharb, Tehran, Iran.
Inorg Chem. 2010 Sep 6;49(17):7773-82. doi: 10.1021/ic1005715.
Density functional theory has been used to analyze the detailed reaction mechanism for the reductive cleavage of CO(2) by a dinitrogen bridged bis-beta-diketoiminatediiron complex, L(tBu)Fe-N(2)-FeL(tBu) (I), recently reported by Holland and co-workers. A number of pathways have been investigated and the most likely mechanism correlates well with experimental evidence. A rationale has been provided for the binding of CO(2), the release of CO, and the ready formation of CO(3)(2-). Our results show that the insertion of CO(2) into the diiron complex is the rate determining step of the reductive cleavage reaction. An intramolecular reduction step from the reduced dinitrogen bridge is proposed which serves to increase the activation of CO(2). This is followed by an intersystem crossing from the septet to the nonet state which acts as a driving force for the subsequent release of CO. The overall reductive cleavage reaction is exergonic by 120 kJ/mol, and further reaction of the released CO with the starting diiron complex is also predicted to be strongly exergonic.
密度泛函理论已被用于分析由双氮桥联双β-二酮亚胺二铁配合物 L(tBu)Fe-N(2)-FeL(tBu)（I）还原裂解 CO2 的详细反应机理，该配合物是 Holland 等人最近报道的。已经研究了多种途径，最可能的机制与实验证据很好地相关。为 CO2 的结合、CO 的释放和 CO3(2-)的易于形成提供了合理的解释。我们的结果表明，CO2 插入二铁配合物是还原裂解反应的速率决定步骤。提出了从还原的二氮桥进行的分子内还原步骤，这有助于增加 CO2 的活化。随后，从七重态到非重态的系间穿越作为随后释放 CO 的驱动力。整个还原裂解反应的自由能变化为-120 kJ/mol，并且预测释放的 CO 与起始二铁配合物的进一步反应也具有很强的自由能变化。
