The N⋅⋅⋅B triel bonds in complexes of boron trihalides, BX3 (X = F, Cl, Br, and I), with species acting as Lewis bases through the nitrogen center, NH3, N2, and HCN, are analyzed theoretically (MP2/aug‐cc‐pVTZ calculations). It is confirmed that stronger Lewis acid properties of the boron center are observed for the BCl3 moiety than for the BF3 one in complexes with the strong Lewis base (NH3); while the opposite order is observed for complexes with the weak Lewis base (N2). The BX3NCH complexes (for X = Cl, Br, and I) are characterized by two tautomeric forms and by two corresponding N⋅⋅⋅B distances, the shorter one possesses characteristics of the covalent bond. In a case of the BF3NCH complex one energetic minimum is observed. Ab initio calculations are supported by an analysis of molecular electrostatic potentials (EPs) and electron density distributions. The quantum theory of ‘atoms in molecules’ and the decomposition of the energy of interaction are applied. The aforementioned acidity orders as well as the existence of two tautomers for some of complexes result partly from the electrostatic interactions' balance; the EP distribution is different for the BF3 species than for the other BX3 species where X = Cl, Br, and I. © 2017 Wiley Periodicals, Inc.

中文翻译：

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三卤化硼配合物中triel键的两个面

理论上分析了三卤化硼 BX3 (X = F、Cl、Br 和 I) 配合物中的 N⋅⋅⋅B triel 键，其中物种通过氮中心 NH3、N2 和 HCN 充当路易斯碱（ MP2/aug-cc-pVTZ 计算）。已证实，BCl3 部分的硼中心比 BF3 与强路易斯碱 (NH3) 形成复合物时观察到更强的路易斯酸性质；而对于弱路易斯碱 (N2) 的配合物则观察到相反的顺序。BX3NCH 复合物（对于 X = Cl、Br 和 I）以两种互变异构形式和两个相应的 N⋅⋅⋅B 距离为特征，较短的具有共价键的特征。在 BF3NCH 复合体的情况下，观察到一个能量最小值。从头算计算得到了分子静电势 (EP) 和电子密度分布分析的支持。应用了“分子中的原子”的量子理论和相互作用能量的分解。上述酸度顺序以及某些配合物的两个互变异构体的存在部分是由于静电相互作用的平衡；BF3 物种的 EP 分布与 X = Cl、Br 和 I 的其他 BX3 物种不同。 © 2017 Wiley Periodicals, Inc.