The Mayer bond order as a tool in inorganic chemistry

The bonding in molecules is most often described using the classical chemic al ideas of covalency (bond multiplicity) and ionicity (atomic charges). Th e Mayer bond order is a natural extension of the Wiberg bond order, which h as proved extremely useful in bonding analysis using semi-empirical computa tional methods, and the Mulliken population analysis to ab initio theories. The usefulness of the Mayer bond order has been tested in a number of inor ganic molecules including sulfur-nitrogen rings, halogen-oxide molecules an d transition metal dichloride molecules. The basis set dependence of the Ma yer bond order is tested through the case studies presented. It is shown th at the bond order can be fully or partially decomposed into the contributio ns from symmetry types for many interactions of interest to the inorganic c hemist. The power of this approach is shown by examining the bonding in a v ariety of systems and is illustrated by detailed studies of the role of the ring size and electron count on the bonding in S-N rings, the role of hype rvalency in the relative stabilities of mixed hydrogen and halogen peroxide isomers and the importance of s-d hybridization in the 3d transition metal dichloride molecules.