Brzeski Jakub, Freza Sylwia, Czapla Marcin, Skurski Piotr
Laboratory of Quantum Chemistry, Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
Henry Eyring Center for Theoretical Chemistry, Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States.
J Phys Chem A. 2021 Mar 25;125(11):2334-2343. doi: 10.1021/acs.jpca.1c00750. Epub 2021 Mar 10.
Grignard reagents are commonly used in organic synthesis, yet their ability to form stable anionic states has not been recognized thus far. In this work, representative examples of RMgF, RMgCl, and RMgBr molecules involving methyl, ethyl, and phenyl functional groups serving as R substituents are investigated regarding their equilibrium structures, adiabatic electron affinities, and vertical electron detachment energies of their daughter anions. The electronic stabilities determined for the negatively charged Grignard compounds are then compared to those predicted for their corresponding magnesium halides. The anions formed by RMgX (R = Me, Et, Ph; X = F, Cl, Br) molecules are found to be adiabatically electronically stable valence-bound systems characterized by relatively large vertical electron detachment energies spanning the 0.79-1.62 eV range. In addition, significant structural relaxation upon attachment of an excess electron is predicted for all Grignard compounds considered. Furthermore, the re-examination of the anions formed by magnesium halides resulted in recognizing them as valence-bound rather than dipole-bound anions, in contrast to the earlier interpretations.
格氏试剂常用于有机合成，但迄今为止它们形成稳定阴离子态的能力尚未得到认可。在这项工作中，研究了以甲基、乙基和苯基官能团作为R取代基的RMgF、RMgCl和RMgBr分子的代表性实例，涉及它们的平衡结构、绝热电子亲和能以及它们的阴离子的垂直电子脱离能。然后将确定的带负电荷的格氏化合物的电子稳定性与其相应卤化镁预测的稳定性进行比较。发现由RMgX（R = 甲基、乙基、苯基；X = 氟、氯、溴）分子形成的阴离子是绝热电子稳定的价键结合体系，其特征是垂直电子脱离能相对较大，范围在0.79 - 1.62电子伏特之间。此外，对于所有考虑的格氏化合物，预计在附着一个多余电子时会有显著的结构弛豫。此外，与早期的解释相反，对卤化镁形成的阴离子的重新研究导致将它们识别为价键结合而非偶极结合的阴离子。
