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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Charge transfer via the dative N-B bond and dihydrogen contacts. Experimental and theoretical electron density studies of four deltahedral boranes
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Charge transfer via the dative N-B bond and dihydrogen contacts. Experimental and theoretical electron density studies of four deltahedral boranes

机译：通过和式N-B键和二氢接触进行电荷转移。四个六面体硼烷的实验和理论电子密度研究

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In an approach combining high resolution X-ray diffraction at low temperatures with density functional calculations, two closo-borates, B _(12)H_(12)~(2-) (1) and B10H 10~(2-) (2), and two arachno-boranes, B_(10)H 12L2 (L = amine (3) or acetonitrile (4)), are studied by means of Atoms In Molecules (AIM) theory and Electron Localizability Indicator (ELI-D). The charge transfer via the dative N-B bonds in the arachno-boranes and via dihydrogen contacts in the closo-borates is quantified. The dative N-B bond in 4 is significantly shorter and stronger than that in 3 and in small N-B Lewis acid base adducts from the literature. It is even shorter in the gas phase than in the crystal environment in contrast to the bond shortening in the crystal generally found for N-B Lewis acid-base adducts. Furthermore, the calculated charge transfer in terms of AIM charges is opposite to the expected N → B direction but still weak as found for all other N-B bonds. The intramolecular charge redistributions due to intermolecular interactions are quantified by the AIM and ELI-D analysis of contact ion pairs. The latter method gives a deeper understanding of delocalization effects in the borane cages as well as in the counterions. Since dihydrogen bonds are rarely found in crystal structures, one focus was directed to the topologies of the large number of 58 experimentally found contacts of this type. The analysis reveals that the electron density at the bond critical point, the corresponding Laplace function, and the curvature along the bond path (λ_3) show a behavior that clearly discriminates these interactions from classical hydrogen bonds, confirming earlier theoretical findings.
机译：在将低温下的高分辨率X射线衍射与密度泛函计算相结合的方法中，两种硼酸盐B_（12）H_（12）〜（2-）（1）和B10H 10〜（2-）（2 ），并通过分子原子（AIM）理论和电子可定位性指示器（ELI-D）研究了两个芳族硼烷B_（10）H 12L2（L =胺（3）或乙腈（4））。定量了通过芳族硼烷中的N-B键间的电荷转移以及通过异硼酸盐中的二氢接触进行的电荷转移。文献中的4中的N-B固定键比3中的N-B短和强得多，在较小的N-B Lewis酸碱加成物中。与通常在N-B Lewis酸碱加合物中发现的键合缩短相比，气相中的键合缩短甚至比晶体环境中的短。此外，根据AIM电荷计算出的电荷转移与预期的N→B方向相反，但仍然弱于所有其他N-B键。通过分子间相互作用产生的分子内电荷再分布通过接触离子对的AIM和ELI-D分析进行定量。后一种方法可以更深入地了解硼烷笼子和抗衡离子中的离域作用。由于在晶体结构中很少发现二氢键，因此将重点放在大量58种通过实验发现的这种类型的触点的拓扑结构上。分析表明，键临界点处的电子密度，相应的拉普拉斯函数和沿键路径的曲率（λ_3）表现出明显区分这些相互作用与经典氢键的行为，从而证实了较早的理论发现。

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