Chemical bonding in hypervalent molecules. The dominance of ionic bonding and negative hyperconjugation over d-orbital participation
14 Feb 1990-Journal of the American Chemical Society (American Chemical Society)-Vol. 112, Iss: 4, pp 1434-1445
TL;DR: In this article, natural population and natural bond orbital analysis is applied to a series of 32-valence-electron species of X{sub 3}XY type (CF{sub 4}, F{sub 2}NO, O{sub 1}PS{sup 3{minus}], F{Sub 3}SN, etc.).
Abstract: Does sulfur form six covalent bonds in CH{sub 3}SO{sub 2}Cl, F{sub 3}S{triple bond}N or carbon or phosphorus five bonds in F{sub 3}C=O{sup {minus}}, F{sub 3}P=O After a brief history of the viewpoints on hypervalent bonding and a comparison of analysis methods (with CH{sub 3}SO{sub 2}Cl as example), natural population and natural bond orbital analysis is applied to a series of 32-valence-electron species of X{sub 3}XY type (CF{sub 4}, F{sub 3}NO, O{sub 3}ClF, O{sub 3}PS{sup 3{minus}}, F{sub 3}SN, etc.). The {sigma}-bonding in these systems is found to be significantly ionic, and the strongly polar {sigma}*{sub AX} orbitals are found to be more effective electron acceptors than the extra-valence d{sub {pi}} (A) orbitals. By generalizing our discussion to n-coordinate 8n-valence-electron species (HF{sub 2}{sup {minus}}, BF{sub 3}, ClO{sub 4}{sup {minus}}, F{sub 4}SO, F{sub 5}TeO{sup {minus}}, IF{sub 6}{sup +}, OXeF{sub 6}, etc.) and their reduced analogues that have one or more lone pairs on the central atom (SF{sub 4}, IF{sub 6}{sup {minus}}, ClF{sub 3}, etc.), we provide a classification of hypervalent (and many nonhypervalent) molecules. The simple, qualitative bonding concepts for hypervalent molecules developed here supercede the inaccurate and misleading dsp{sup 3} and d{sup 2}sp{sup 3} models that are still in widespread use.
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