Unusual Five-Center,Four-Electron Bonding in a Rhodium–Bismuth Complex with Pentagonal-Bipyramidal Geometry

A better understanding of the chemical bond in general is gained from the electronic structure of the molecular complex [{RhBi₇}Br₈]. The interactions in the central Bi₅ ring can be interpreted as an unusual five-center, four-electron bond based on ab initio calculations and group theory. Of the linear combinations of five Bi p orbitals two of the molecular orbitals are binding (depicted in the sketch).