The molecular interactions between phosphorous ylide (PY) and HX molecules (X = F, CN, and N3) were investigated using the MP2 method at 6-311++G(2d,2p) basis set. Three different patterns including non-classical hydrogen bond H···C, X···P interaction and classical hydrogen bond H···X were found for complex formation between PY and HX molecules. From the predicted models, stability of the H···C type complexes are greater than other types. Quantum theories of atoms in molecules and natural bond orbitals methods have been applied to analyze the intermolecular interactions. Good correlations have been found between the interaction energies (SE), the second-order perturbation energy E (2), and the charge transfer qCT in the studied systems.
