Pnicogen and hydrogen bonds: complexes between PH3X(+) and PH2X systems.

The charge-assisted complexes between PH3X(+) and PH2X have been analyzed. MP2/aug'-cc-pVTZ calculations were performed and the results were supported by the Quantum Theory of Atoms in Molecules approach and the Natural Bond Orbitals method. It was found that three different configurations could be formed, i.e. those linked through a P···P or a P···X pnicogen bond and those linked through a P-H···P hydrogen bond. The P···P configurations are the most stable ones corresponding to the strongest interactions; for all complexes the P···P configuration exists, while the P···X and P-H···P ones are present only for some of them. Different relations between the parameters were found, especially for the P···P interactions where there are correlations between the P···P distance and the electron density at the P···P bond critical point (ρPP) as well as between ρPP and the charge transfer energy.