Searching for the ylide structure. An ab initio study of the H2O…CCl2 complex

The potential energy surface (PES) for the H2O…CCl2 complex has been investigated at the self-consistent field level with a DZP basis set in order to search for stationary points and to verify the possible formation of an ylide species. Six stationary points were located on the PES, being one minimum, three first-order transition states (TS) and two second-order TS structures. A stable ylide species was not found, and an explanation for this is given based on electrostatic grounds. The unique minimum corresponds to an H-bond structure, with a dissociation energy of 845.5 cm−1, calculated including zero point energy correction, a more extended basis set, electron correlation effects at the MP2 level and taking into account basis set superposition errors employing the counterpoise method.