Influence of hydrogen bonds on the P⋯P pnicogen bond

Abstract

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:(PH 2F) 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:(PH 2F) 2 and 3FH:(PH 2F) 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 P 2H 4. The dramatic changes in these two complexes reflect the changing nature of the hydrogen bonds and the pnicogen bond. Thus, the complex 3FH:(PH 2F) 2 acquires ion-pair character represented as [3(FH)F -:(H 2P-PH 2F) +], and the P⋯P pnicogen bond acquires significant covalent character. These changes are observed to a lesser extent in 2FH:(PH 2F) 2. © 2012 American Chemical Society.