J. Chem. Theor. Comput. 8, 2320-2327 (2012)

DOI: 10.1021/ct300399y

Influence of Hydrogen Bonds on the P...P Pnicogen Bond

Ab initio MP2/aug′-cc-pVTZ calculations have been carried out to investigate the influence of F–H···F hydrogen bonds on the P···P pnicogen bond in complexes nFH:(PH2F)2 for n = 1–3. The formation of F–H···F hydrogen bonds leads to a shortening of the P–P distance, a lengthening of the P–F distance involved in the hydrogen bond, a strengthening of the P···P interaction, and changes in atomic populations, NMR 31P chemical shieldings, and 1pJ(P–P) coupling constants. The magnitude of these changes depends on the number of FH molecules and their positions in the complex and are relatively modest except for complexes 2FH:(PH2F)2and 3FH:(PH2F)2 that have all FH molecules hydrogen bonded to the same F-atom. For these two complexes, 1pJ(P–P) decreases as the P–P distance decreases and approaches the value of 1J(P–P) for P2H4. The dramatic changes in these two complexes reflect the changing nature of the hydrogen bonds and the pnicogen bond. Thus, the complex 3FH:(PH2F)2 acquires ion-pair character represented as [3(FH)F:(H2P–PH2F)+], and the P···P pnicogen bond acquires significant covalent character. These changes are observed to a lesser extent in 2FH:(PH2F)2