Braida Benoit, Ribeyre Tristan, Hiberty Philippe C
Sorbonne Université, UPMC Univ Paris 06, UMR 7616, LCT, F-75005 Paris (France), Fax: (+33) 1-44-27-41-17; CNRS, UMR 7616, LCT, F-75005 Paris (France).
Chemistry. 2014 Jul 28;20(31):9643-9. doi: 10.1002/chem.201402755. Epub 2014 Jun 26.
Some typical hypervalent molecules, SF4 , PF5 , and ClF3 , as well as precursors SF ((4) Σ(-) state) and SF2 ((3) B1 state), are studied by means of the breathing-orbital valence bond (BOVB) method, chosen for its capability of combining compactness with accuracy of energetics. A unique feature of this study is that for the first time, the method used to gain insight into the bonding modes is the same as that used to calculate the bonding energies, so as to guarantee that the qualitative picture obtained captures the essential physics of the bonding system. The (4) Σ(-) state of SF is shown to be bonded by a three-electron σ bond assisted by strong π back-donation of dynamic nature. The linear (3) B1 state of SF2 , as well as the ground states of SF4 , PF5 and ClF3 , are described in terms of four VB structures that all have significant weights in the range 0.17-0.31, with exceptionally large resonance energies arising from their mixing. It is concluded that the bonding mode of these hypervalent species and isoelectronic ones complies with Coulson's version of the Rundle-Pimentel model, but assisted by charge-shift bonding. The conditions for hypervalence to occur are stated.
通过呼吸轨道价键（BOVB）方法研究了一些典型的高价分子，如SF₄、PF₅和ClF₃，以及前体SF（（⁴）Σ⁻态）和SF₂（（³）B₁态），选择该方法是因其能够将紧凑性与能量学的准确性相结合。本研究的一个独特之处在于，首次用于深入了解键合模式的方法与用于计算键能的方法相同，以确保所获得的定性图像能够捕捉键合系统的基本物理性质。结果表明，SF的（⁴）Σ⁻态通过一个三电子σ键结合，并伴有动态性质的强π反馈。SF₂的线性（³）B₁态以及SF₄、PF₅和ClF₃的基态，是根据四个VB结构来描述的，它们在0.17 - 0.31范围内都具有显著的权重，并且由于它们的混合而产生了异常大的共振能。得出结论，这些高价物种和等电子物种的键合模式符合库尔森版本的朗德尔 - 皮门特尔模型，但有电荷转移键合的辅助。阐述了高价态出现的条件。
