Double π-hole tetrel-chalcogen interactions can lead to stable molecular heterodimer

A thorough topological investigation is used to study the possible isomers of (SO3)(H2XY) complexes, for X=C, Si and Y=O, S. From the topological properties of the isolated monomers, up to five types of isomers can be considered, depending on the nature of the X and Y atoms. After geometry optimisations, three isomers belonging to four different types of geometry were obtained. The natures of the X and Y atoms not only affect the relative stability of the isomers, but also the interaction sites available on the H2XY molecule. For all the systems considered in this study, a covalent structure was obtained from a non-covalent isomeric form involving a double -hole interaction. Such a covalent structure corresponds to the global minimum for the (SO3)(H2CS), (SO3)(H2SiO) and (SO3)(H2SiS) complexes, and a local minimum for the (SO3)(H2CO) complex. The usefulness of physically-relevant topological tools for a thorough characterisation of the monomers prior to a search for the isomeric forms of a complex is once again demonstrated.