Theoretical study of Ha⟨-P and Xa⟨-P interactions of methylphosphines with HSX molecules

Ab initio calculations were used to analyze the interactions between thiohypohalous acids (HSX; X = F, Cl, Br, I) and methylphosphine derivatives (PH (n) Me3-n , n = 0-3) at the MP2/aug-cc-pVDZ level of theory. Interaction of HSX with PH (n) Me3-n leads to both hydrogen bond (HSX-PH (n) Me3-n -HB) as well as halogen bond (HSX-PH (n) Me3-n -XB) complexes. Stabilities of both HB and XB complexes increase with basicity of the phosphines. However, HB complexes of a phosphine molecule with different HSX have the same order of stabilities, but XB complexes of heavier thiohypohalous acids are more stable. Electron densities of complexes were characterized with the atoms in molecules methodology. The charge transfer within dimers was analyzed by means of natural bond orbitals.