Beyond the Classical Electron-Sharing and Dative Bond Picture: The Case of Spin-Polarized Bond

Chemical bonds are traditionally assigned as electron-sharing or donor-acceptor/dative. External criteria such as the nature of the dissociation process, energy partitioning schemes, or quantum chemical topology are invoked to assess the bonding situation. However, for systems with marked multi-reference character, this binary categorization might not be precise enough to render the bonding properties. A third scenario can be foreseen: spin polarized bonds. To illustrate this, the case of a NaBH3- cluster is presented. According to the analysis, NaBH3- exhibits a strong diradical character and cannot be classified as electron-sharing or dative bond. Elaborated upon are the common problems of popular bonding description. Additionally, a simple model, based on the bond order and local spin indicators, which discriminates between all three bonding situations, is provided.

Automated summary

This article discusses the classification of chemical bonds, pointing out that the traditional categorization of electron-sharing or donor-acceptor/dative bonds may not be accurate enough to describe the bonding properties of certain systems. A third possibility is proposed: spin polarized bonds, illustrated by the case of a NaBH3- cluster. Furthermore, a simple model based on bond order and local spin indicators is provided to distinguish between all three bonding situations.