Tang Chuan-Kai, Li Ya-Zhou, Ma Fang, Cao Zexing, Mo Yirong
School of Chemistry and Materials Science, Huaibei Normal University, Huaibei 235000, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemistry Engineering, Xiamen University, Xiamen 361005, China.
J Phys Chem Lett. 2021 Aug 12;12(31):7545-7552. doi: 10.1021/acs.jpclett.1c02134. Epub 2021 Aug 4.
There has been growing interest in the CO capture and reduction by transition-metal-free catalysts. Here we performed a proof-of-concept study using an ab initio valence bond method called the block-localized wave function (BLW) method. The integrated BLW and density function theory (DFT) computations demonstrated that heterobimetallic Ae/Al(I) (Ae represents alkaline earth metals Mg and Ca) Lewis acid/base combinations without transition metals can facilely capture and activate CO. There are two remarkable findings in this study. The first concerns the ionic nature of the metal-metal bonds. The experimentally synthesized low valent aluminum compound with a bidentate β-diketiminate (BDI) ligand, or (BDI)Al(I) in brief, is a Lewis base due to the lone pair on the aluminum cation though overall Al(I) is positively charged. Al(I) can form ionic metal-metal bonds with the alkaline earth metals of the positively charged Lewis acids (BDI)Ae. This type of ionic metal-metal bonds is counterintuitive and antielectrostatic as both metals carry positive charges. The second finding is the CO activation mechanism. (BDI)Al(I) can effectively bind and activate CO by transferring one electron to CO, and the resulting complex can be best expressed as [(BDI)Al(I)][CO]. The participation of (BDI)Ae further enhances the capture and activation of CO by (BDI)Al(I).
无过渡金属催化剂用于捕获和还原一氧化碳的研究日益受到关注。在此，我们使用一种名为块定域波函数（BLW）方法的从头算价键方法进行了一项概念验证研究。结合BLW和密度泛函理论（DFT）的计算表明，不含过渡金属的异双金属Ae/Al（I）（Ae代表碱土金属Mg和Ca）路易斯酸/碱组合能够轻松捕获并活化一氧化碳。本研究有两个显著发现。第一个涉及金属 - 金属键的离子性质。实验合成的带有双齿β - 二酮亚胺（BDI）配体的低价铝化合物，简称为（BDI）Al（I），尽管整体Al（I）带正电荷，但由于铝阳离子上的孤对电子，它是一种路易斯碱。Al（I）可以与带正电荷的路易斯酸（BDI）Ae的碱土金属形成离子型金属 - 金属键。这种离子型金属 - 金属键是违反直觉且反静电的，因为两种金属都带正电荷。第二个发现是一氧化碳的活化机制。（BDI）Al（I）可以通过向一氧化碳转移一个电子来有效地结合并活化一氧化碳，生成的配合物最好表示为[(BDI)Al(I)][CO]。（BDI）Ae的参与进一步增强了（BDI）Al（I）对一氧化碳的捕获和活化。
