Yáñez Manuel, Mó Otilia, Montero-Campillo M Merced, Alkorta Ibon, Elguero José
Departamento de Química, Módulo 13, Facultad de Ciencias, and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, Madrid, Spain.
Instituto de Química Médica, IQM-CSIC, Madrid, Spain.
J Comput Chem. 2025 Jan 5;46(1):e27509. doi: 10.1002/jcc.27509. Epub 2024 Sep 28.
In this study, we investigate the protonation effects on the structure, relative stability and basicity of complexes formed by the interaction of monomers and dimers of BeX and MgX (X = H, F) with NH, CHNH, HCN, and NCH bases. Calculations were performed using the M06-2X/aug-cc-pVTZ formalism, along with QTAIM, ELF and NCI methods for electron density analysis and MBIE and LMO-EDA energy decomposition analyses for interaction enthalpies. The protonation of the MH- and MH-Base complexes occurs at the negatively charged hydrogen atoms of the MH and MH moieties through typical hydride abstraction reactions, while protonation at the N atom of the base is systematically less exothermic. The preference for the hydride transfer mechanism is directly associated with the significant exothermicity of H formation through the interaction between H and H, and the high hydride donor ability of these complexes. The basicity of both, MH and MH compounds increases enormously upon association with the corresponding bases, with the increase exceeding 40 orders of magnitude in terms of ionization constants. Due to the smaller exothermicity of HF formation, the basicity of fluorides is lower than that of hydrides. In Be complexes, the protonation at the N atom of the base dominates over the fluoride abstraction mechanism. However, for the Mg complexes the fluoride abstraction mechanism is energetically the most favorable process, reflecting the greater facility of Mg complexes to lose F.
在本研究中，我们研究了质子化对由BeX和MgX（X = H，F）的单体和二聚体与NH、CHNH、HCN和NCH碱相互作用形成的配合物的结构、相对稳定性和碱性的影响。使用M06 - 2X/aug - cc - pVTZ形式进行计算，并结合QTAIM、ELF和NCI方法进行电子密度分析，以及MBIE和LMO - EDA能量分解分析进行相互作用焓分析。MH - 和MH - 碱配合物的质子化通过典型的氢化物提取反应发生在MH和MH部分带负电荷的氢原子上，而碱的N原子上的质子化在系统上放热较少。对氢化物转移机制的偏好直接与通过H和H之间的相互作用形成H的显著放热以及这些配合物的高氢化物供体能力相关。与相应碱缔合后，MH和MH化合物的碱性都大幅增加，就电离常数而言，增加超过40个数量级。由于HF形成的放热较小，氟化物的碱性低于氢化物。在Be配合物中，碱的N原子上的质子化比氟化物提取机制占主导。然而，对于Mg配合物，氟化物提取机制在能量上是最有利的过程，这反映了Mg配合物更容易失去F。
