Charge-shift bonding - A class of electron-pair bonds that emerges from valence bond theory and is supported by the electron localization function approach

Sason Shaik*, David Danovich, Bernard Silvi, David L. Lauvergnat, Philippe C. Hiberty

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

235 Scopus citations

Abstract

This paper deals with a central paradigm of chemistry, the electron-pair bond. Valence bond (VB) theory and electron-localization function (ELF) calculations of 21 single bonds demonstrate that along the two classical bond families of covalent and ionic bonds, there exists a class of charge-shift bonds (CS bonds) in which the fluctuation of the electron pair density plays a dominant role. In VB theory, CS bonding manifests by way of a large covalent-ionic resonance energy, RECS, and in ELF by a depleted basin population with large variances (fluctuations). CS bonding is shown to be a fundamental mechanism that is necessary to satisfy the equilibrium condition, namely the virial ratio of the kinetic and potential energy contributions to the bond energy. The paper defines the atomic propensity and territory for CS bonding: Atoms (fragments) that are prone to CS bonding are compact electronegative and/or lone-pair-rich species. As such, the territory of CS bonding transcends considerations of static charge distribution, and in volves: a) homopolar bonds of heteroatoms with zero static ionicity, b) heteropolar σo and π bonds of the electronegative and/or electron-pair-rich elements among themselves and to other atoms (e.g., the higher metalloids, Si, Ge, Sn, etc), c) all hypercoordinate molecules. Several experimental manifestations of charge-shift bonding are discussed, such as depleted bonding density, the rarity of ionic chemistry of silicon in condensed phases, and the high barriers of halogen-transfer reactions as compared to hydrogen-transfers.

Original languageEnglish
Pages (from-to)6358-6371
Number of pages14
JournalChemistry - A European Journal
Volume11
Issue number21
DOIs
StatePublished - 21 Oct 2005

Keywords

  • Bond theory
  • Charge-shift bonding
  • Electron pairing
  • ELF (electron localization function)
  • Valence bond

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