What can we learn from two‐center three‐electron bonding with the topological analysis of ELF? (original) (raw)

In this paper, a review is presented of the abundant literature on the two‐center three‐electron (2c‐3e) bonding, which plays a crucial role in electron transfer and radical chemistry. Important questions regarding this peculiar type of interaction are (1) Is a three‐electron bonded complex a molecule or an assembly of molecules?, (2) Since an unpaired electron is involved, where is the spin density located?, and (3) Is there a descriptor of electron fluctuation, which is a central phenomenon in this type of bonding? We demonstrate that the topological analysis of the electron localization function (ELF), which provides a convenient mathematical framework to study chemical bond in molecules and solids, is able to answer these questions. First, examples of potentially 3e‐bonded complexes proposed by Pauling are reinvestigated. Second, the electron attachment process on molecules of the HnXYHm type with X,Y = Cl, S, P, Si and n, m = 0–2 is considered. Finally, the ELF‐based topology o...