Neither too Classic nor too exotic: One-electron Na·B Bond in NaBH3- Cluster.

It is hereby reported that NaBH 3 -  cluster exhibits a Na·B one-electron bond, a well-established type of electron-deficient bonding in the literature. The topological analysis of the electron localization function, at the correlated level, reveals that Na - , when approaching the bonding distance, fairly distributes its valence electron pair between two lobes. One of these electrons is used to bond with BH 3 , which participates through its boron empty  p -orbital. Furthermore, the bonding situation of LiBH 3 - , KBH 3 - , MgBH 3 , and CaBH 3  global minima structures are similar to that of NaBH 3 - , extending the family of these new one-electron bond systems with biradicaloid character.