Simultaneous Occurrence of Quadruple Lewis Acid-Base Interactions between Selenium Atoms in Selenocarbonyl Dimers

High-level quantum chemical calculations are performed to investigate C=Se⋅⋅⋅Se=C interactions. Bounded structures are found with binding energies between -4 and -7 kJ mol^-1 . An energy decomposition analysis shows that dispersion is the more attractive term, and in all cases save one, the electrostatic interaction is attractive despite each selenium atom having a positive σ-hole at the extension of the C=Se bond. The topological analysis of the molecular electrostatic potential and L(r)=-∇² ρ(r) function, and natural bond orbital analysis reveal that these particular Se⋅⋅⋅Se contacts can be considered to be quadruple Lewis acid-base interactions.