Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35043 Marburg, Germany.
J Phys Chem A. 2009 Oct 29;113(43):11693-8. doi: 10.1021/jp902780t.
DFT calculations at the BP86/TZ2P level have been carried out for the compounds OCBBCO, N(2)BBN(2), and OBBBBO. The calculations predict very short distances and large bond dissociation energies for the central B-B bonds. The nature of the bonding situation was investigated with an energy decomposition analysis. It shows that the central boron-boron bonds are genuine triple bonds. The pi-bonding contributes between 38-40% to the total orbital interactions of the B[triple bond]B bonds. The compounds can be considered as donor-acceptor complexes L-->BB<--L between the central B(2) moiety in the third [(3)(1)Sigma(g)(+)] excited state and the ligands L = CO, N(2), BO(-). The pi-backdonation L<--BB-->L for L = CO, N(2) is very strong, which suggests that the latter bonds should also be considered as triple bonds. The pi-bonding in OB<--BB-->BO is weaker, which makes the latter bonds borderline cases for triple bonds. The triple-bond character explains the very large bond dissociation energies for the LB-BL and L-BB-L bonds.
在 BP86/TZ2P 水平上进行了 OCBBCO、N(2)BBN(2)和OBBBBO化合物的密度泛函理论计算。这些计算预测了中心 B-B 键的非常短的距离和大的键离解能。通过能量分解分析研究了键合情况的本质。结果表明，中心硼-硼键是真正的三键。π键合对 B[三重键]B 键的总轨道相互作用的贡献在 38-40%之间。这些化合物可以被认为是在第三 [(3)(1)Sigma(g)(+)]激发态的中心 B(2)部分和配体 L = CO、N(2)、BO(-)之间的供体-受体配合物 L-->BB<--L。对于 L = CO、N(2)，π-backdonation L<--BB-->L 非常强，这表明后者也应该被认为是三键。OB<--BB-->BO中的π键合较弱，这使得后者的键成为三键的边界情况。三键特征解释了 LB-BL 和 L-BB-L 键的非常大的键离解能。
