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

High-level quantum chemical calculations are performed to investigate C=SeSe=C interactions. Bounded structures are found with binding energies between -4 and -7kJmol(-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 sigma-hole at the extension of the C=Se bond. The topological analysis of the molecular electrostatic potential and L(r)=-delta(2)(r) function, and natural bond orbital analysis reveal that these particular SeSe contacts can be considered to be quadruple Lewis acid-base interactions.