The FCH₂CN–BCl₃ and ClCH₂CN–BCl₃ complexes were investigated by quantum-chemical computations and low-temperature, matrix-isolation-IR spectroscopy. Theory predicts two stable equilibrium structures, with distinctly different B–N distances, for both complexes. One set of structures, which correspond to the global energy minima, exhibit B–N distances of 1.610 and 1.604 Å for FCH₂CN–BCl₃ and ClCH₂CN–BCl₃, respectively (via M06-2X/aug-cc-pVTZ). The corresponding binding energies are 5.3 and 6.3 kcal/mol. For the metastable structures, the B–N distances are 2.870 and 2.865 Å for FCH₂CN–BCl₃ and ClCH₂CN–BCl₃, respectively, and the corresponding binding energies are 3.2 and 3.3 kcal/mol. Also, the barriers between these structures on the B–N distance potentials are 2.5 and 2.8 kcal/mol, respectively, relative to the secondary, long-bond minima. In addition, several IR bands of both FCH₂CN–BCl₃ and ClCH₂CN–BCl₃ were observed in nitrogen matrices, but the assigned bands are consistent with M06-2X predictions for the short-bond, minimum-energy structures. None of the observed IR bands could be assigned to the metastable, long-bond structures.

中文翻译：

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卤代乙腈-BCl ₃配合物的结构和能量性质：计算和基体红外光谱

FCH ₂ CN–BCl ₃和ClCH ₂ CN–BCl ₃配合物通过量子化学计算和低温，基体-隔离-IR光谱进行了研究。理论预测两种配合物都有两个稳定的平衡结构，其B–N距离明显不同。一组对应于全球最低能量的结构，对于FCH ₂ CN-BCl ₃和ClCH ₂ CN-BCl ₃，其B–N距离分别为1.610和1.604Å （通过M06-2X / aug-cc-pVTZ ）。相应的结合能为5.3和6.3kcal / mol。对于亚稳结构，FCH ₂ CN–BCl ₃的B–N距离为2.870和2.865Å和ClCH ₂ CN–BCl ₃，相应的结合能分别为3.2和3.3 kcal / mol。同样，相对于第二个长键极小值，B–N距离电势上这些结构之间的势垒分别为2.5和2.8 kcal / mol。此外，在氮气基质中观察到了FCH ₂ CN–BCl ₃和ClCH ₂ CN–BCl _3的多个红外波段，但分配的波段与M06-2X对短键，最小能量结构的预测一致。观察到的红外波段均不能分配给亚稳的长键结构。