不同甲基卤化物中的C-X键断裂(CH3X;X=Cl,Br,I)在本工作中从理论上研究了5,6-二甲基苯并咪唑-双(二甲基乙二肟)钴(II)(CoIICbx)介导的。SN2样机理被认为模拟了其中钴原子充当亲核试剂和卤素充当离去基团的化学过程。利用内在反应坐标法计算了反应路径,并通过反作用力形式主义进行了详细分析,分子中原子的量子理论(QTAIM),以及单电子密度导出量的计算,例如源函数(SF)和自旋密度。将结果与在5,6-二甲基苯并咪唑-双(二甲基乙二肟酸)钴(I)(CoICbx)存在下进行的相同反应中获得的结果进行了彻底比较,以揭示两种情况之间的主要差异。与存在CoICbx络合物的反应相比,观察到由CoIICbx介导的反应是吸热的并且具有更高的活化能。后者得到了反作用力结果的支持,这表明了活化能与裂解反应中存在的不同亲核试剂的电离势之间的关系。此外,SF结果表明,较低的轴向配体(即,5,6-二甲基苯并咪唑)仅参与由CoIICbx络合物介导的反应的第一阶段,而对于CoICbx的案子,它似乎在整个过程中起着重要作用。最后,QTAIM电荷分析表明,两种情况下都会发生钴原子的氧化;同时,这表明在CoIICbx情况下形成了不常见的两中心单电子键。后者通过电子定位计算得到证实,与CoIICbx对应物相比,这导致CoICbx情况在Co-C原子间区域的电子计数更大。
The C-X bond cleavage in different methyl halides (CH3X; X = Cl, Br, I) mediated by 5,6-dimethylbenzimidazole-bis(dimethylglyoximate)cobalt(II) (CoIICbx) was theoretically investigated in the present work. An SN2-like mechanism was considered to simulate the chemical process where the cobalt atom acts as the nucleophile and the halogen as the leaving group. The reaction path was computed by means of the intrinsic reaction coordinate method and analyzed in detail through the reaction force formalism, the quantum theory of atoms in molecules (QTAIM), and the calculation of one-electron density derived quantities, such as the source function (SF) and the spin density. A thorough comparison of the results with those obtained in the same reaction occurring in presence of 5,6-dimethylbenzimidazole-bis(dimethylglyoximate)cobalt(I) (CoICbx) was conducted to reveal the main differences between the two cases. The reactions mediated by CoIICbx were observed to be endothermic and possess higher activation energies in contrast to the reactions where the CoICbx complex is present. The latter was supported by the reaction force results, which suggest a relationship between the activation energy and the ionization potentials of the different nucleophiles present in the cleavage reaction. Moreover, the SF results indicates that the lower axial ligand (i.e., 5,6-dimethylbenzimidazole) exclusively participates on the first stage of the reaction mediated by the CoIICbx complex, while for the CoICbx case, it appears to have an important role along the whole process. Finally, the QTAIM charge analysis indicates that oxidation of the cobalt atom occurs in both cases; at the same time, it suggests the formation of an uncommon two-center one-electron bond in the CoIICbx case. The latter was confirmed by means of electron localization calculations, which resulted in a larger electron count at the Co-C interatomic region for the CoICbx case upon comparison with its CoIICbx counterpart.