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A Valence Bond Model for Electron‐Rich Hypervalent Species: Application to SF n ( n =1, 2, 4), PF 5 , and ClF 3
Author(s) -
Braida Benoit,
Ribeyre Tristan,
Hiberty Philippe C.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402755
Subject(s) - hypervalent molecule , valence (chemistry) , intermolecular force , valence electron , atomic physics , chemistry , electron , molecule , valence bond theory , ground state , computational chemistry , physics , molecular orbital , quantum mechanics , organic chemistry , reagent
Some typical hypervalent molecules, SF 4 , PF 5 , and ClF 3 , as well as precursors SF ( 4 Σ − state) and SF 2 ( 3 B 1 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 B 1 state of SF 2 , as well as the ground states of SF 4 , PF 5 and ClF 3 , 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.