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, we present the case of NaBH 3 - cluster. According to our analysis, NaBH 3 - exhibits a strong diradical character and cannot be classified as electron-sharing or dative bond . We elaborate on the common problems of popular bonding description. Additionally, we provide a simple model, based on the bond order and local spin indicators, which discriminates between all three bonding situations.