Valence-bond description of electrons

Vol. 30 R.D. Harcourt, Qualitative Valence-Bond Descriptions of Electron-Rich Molecules Pauling 3-Electron Bonds and Increased-Valence Theory. X, 260 pages. 1982. 

R. D. Harcourt, Qualitative Valence Bond Descriptions of Electron-Rich Molecules... 

MULTIREFERENCE PERTURBATION THEORY AND VALENCE BOND DESCRIPTION OF ELECTRONIC STRUCTURES OF MOLECULES... 

Harcourt, R.D. J. Chem. Educ. 1968,45, 779 Qualitative Valence-Bond Description of Electron-Rich molecules. Pauling "3-Electron Bonds" and "Increased-Valence" Theory, Lectures Notes in Chem., Springer-Verlag, vol. 30, 1982, chap. 4,10-12, 16. 

For a different qualitative VB treatment of Inorganic molecules. Including "hypervalent" molecules, the reader Is referred to the Interesting work of Harcourt Harcourt, R,D. Qualitative Valence-Bond Description of Electron-Rich Molecules , Lecture Notes In Chemistry, Vol. 30 Sprlnger-Verlag ... 

We are therefore led to conclude that all increased-valence structures for 4-electron 3-centre bonding units can have Pauling 3-electron bonds as components of their valence-bond structures. And because the phenomenon of 4-electron 3-centre bonding occurs extremely frequently, it follows that the relevance of Pauling 3-electron bond and increased-valence theory for qualitative valence-bond descriptions of electronic structure is very great. The need for an increased-valence theory has also been implied by Bent in his review on inter- and intramolecular donor and acceptor complexes. 

For the ground-states of other electron-rich molecules, the results of valence-bond calculations from different laboratories - see for example references 24-29 of Chapter 2 - also indicate also indicate that long-bond structures are more important than is usually supposed, and therefore they need to be included in qualitative valence-bond descriptions of their electronic stmcture. This book describes how this can be done, and some of the resulting consequences for the interpretation of the electronic structure, bond properties and reaction mechanisms for various electron-rich molecules. When appropriate, molecular orbital and valence-bond descriptions of bonding are compared, and relationships that exist between them are derived. Considerable attention is given to the use of Pauling 3-electron bonds (A--B as A-B) for providing qualitative valence-bond descriptions of electronic structure. The increased-valence structures for electron-rich molecules - for example... 

The increased-valence theory represents a natural extension of the more familiar Lewis-Pauling valence-bond theory. Therefore an understanding of it may be useful for all chemists who have an interest in qualitative valence-bond descriptions of electronic structure. It will be shown that all Lewis-type valence-bond structures with lone-pairs of electrons can be stabilized easily via one-electron delocalizations from doubly-occupied atomic orbitals into diatomic bonding molecular orbitals when the relevant atomic orbitals overlap, as is shown here for the two sets of oxygen n electrons of N2O. 

According to Lewis s approach and valence-bond theory, we should describe the bonding in 02 as having all the electrons paired. However, oxygen is a paramagnetic gas (Fig. 3.24 and Box 3.2), and paramagnetism is a property of unpaired electrons. The paramagnetism of 02 therefore contradicts both the Lewis structure and the valence-bond description of the molecule. 

Modern Valence-Bond Description of the Mechanisms of Six-Electron Pericyclic Reactions... 

Modern valence-bond description of the mechanisms of six-electron 327... 

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