Valence bond theory nomenclature

Restricting ourselves to a six-coordinated system and to the valence bond theory and crystal field theory, it is possible to illustrate the bonding in complexes and to designate the nomenclature using [CoFe] and [Co(NH3)e] + as examples. It is first necessary to know that [CoFs] is paramagnetic with four unpaired electrons, whereas [Co(NH3) ] + is diamagnetic. On the basis of the valence bond theory the electronic structures are designated as ( 5) or cPsp (6) hybridizations. 

Modem quantum-mechanical Valence-Bond (VB) theory has firm roots back to classical ideas even of a century and a half ago. These connections are of special interest, especially if greater general insight and extension of the classical concepts can be made. The interconnecting simpler semiempirical approaches, such as are of the prime focus here, are historically inextricably mixed with that of the ab initio theory, and the development has been via a peculiarly torturous road toward quantitative relevance. Thence here some brief historical commentary which also sets some nomenclature and ideas is first made. 

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