Electron-pair bonds, theoretical treatment

Since rigorous theoretical treatments of molecular structure have become more and more common in recent years, there exists a definite need for simple connections between such treatments and traditional chemical concepts. One approach to this problem which has proved useful is the method of localized orbitals. It yields a clear picture of a molecule in terms of bonds and lone pairs and is particularly well suited for comparing the electronic structures of different molecules. So far, it has been applied mainly within the closed-shell Hartree-Fock approximation, but it is our feeling that, in the future, localized representations will find more and more widespread use, including applications to wavefunctions other than the closed-shell Hartree-Fock functions. 

The [WsXg]44 clusters are diamagnetic and with the 24 available metal electrons there is a metal-metal bond of order one between each pair of tungsten atoms, in agreement with theoretical treatment of the electronic structure of these clusters.354,355... 

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