Ying Fei, Yuan Xu, Zhang Xinxing, Xie Jing
Key Laboratory of Cluster Science of Ministry of Education, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
College of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCAST), Tianjin Key Laboratory of Biosensing and Molecular Recognition, Shenzhen Research Institute, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin 300071, China.
Molecules. 2022 Nov 21;27(22):8069. doi: 10.3390/molecules27228069.
Halogen bonds (XBs) between metal anions and halides have seldom been reported because metal anions are reactive for XB donors. The pyramidal-shaped Mn(CO) anion is a candidate metallic XB acceptor with a ligand-protected metal core that maintains the negative charge and an open site to accept XB donors. Herein, Mn(CO) is prepared by electrospray ionization, and its reaction with CHI in gas phase is studied using mass spectrometry and density functional theory (DFT) calculation. The product observed experimentally at m/z = 337 is assigned as [IMn(CO)(OCCH)], which is formed by successive nucleophilic substitution and reductive elimination, instead of the halogen-bonded complex (XC) CH-I···Mn(CO), because the I···Mn interaction is weak within XC and it could be a transient species. Inspiringly, DFT calculations predict that replacing CHI with CFI can strengthen the halogen bonding within the XC due to the electro-withdrawing ability of F. More importantly, in so doing, the nucleophilic substitution barrier can be raised significantly, ~30 kcal/mol, thus leaving the system trapping within the XC region. In brief, the combination of a passivating metal core and the introduction of an electro-withdrawing group to the halide can enable strong halogen bonding between metallic anion and iodide.
金属阴离子与卤化物之间的卤键（XB）鲜有报道，因为金属阴离子对XB供体具有反应活性。金字塔形的Mn(CO)阴离子是一种潜在的金属XB受体，其配体保护的金属核心可维持负电荷并提供一个接受XB供体的开放位点。在此，通过电喷雾电离制备了Mn(CO)，并使用质谱和密度泛函理论（DFT）计算研究了其在气相中与CHI的反应。实验观察到的质荷比为m/z = 337的产物被确定为[IMn(CO)(OCCH)]，它是通过连续的亲核取代和还原消除形成的，而不是卤键复合物（XC）CH-I···Mn(CO)，因为XC内的I···Mn相互作用较弱，它可能是一种瞬态物种。令人鼓舞的是，DFT计算预测，由于F的吸电子能力，用CFI取代CHI可以增强XC内的卤键。更重要的是，这样做可以显著提高亲核取代势垒，约30 kcal/mol，从而使体系被困在XC区域内。简而言之，钝化金属核心与在卤化物中引入吸电子基团相结合，可以实现金属阴离子与碘化物之间的强卤键。
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