Detecting delocalization

Abstract

As the bonding in many compounds can be adequately described using localized, two-centre two-electron bonds, the electronic structure of molecules where such a description is inadequate is often chemically very interesting. Three-centre bond orders provide a useful tool for detecting the presence and analyzing the importance of multicentre and hypervalent effects. To depict the resulting chemical structures, a graphical device is introduced which constructs the chemical connections ab initio from the electronic structure. The three-centre, two-electron bonding in a set of electron-deficient boranes and the three-centre, four-electron bonding in a set of electron-rich xenon fluorides has been analyzed and the approach has been used to test for the occurrence and importance of pseudo-aromatic, closed-loops in polyoxometalates.