Structures, Energies, Bonding, and NMR Properties of Pnicogen Complexes H₂XP:NXH₂(X ═ H, CH₃, NH₂, OH, F, Cl)

Abstract

Ab initio calculations have been carried out in a systematic investigation of P···N pnicogen complexes H(2)XP:NXH(2) for X ═ H, CH(3), NH(2), OH, F, and Cl, as well as selected complexes with different substituents X bonded to P and N. Binding energies for complexes H(2)XP:NXH(2) range from 8 to 27 kJ mol(-1) and increase to 39 kJ mol(-1) for H(2)FP:N(CH(3))H(2). Equilibrium structures have a nearly linear A-P-N arrangement, with A being the atom directly bonded to P. Binding energies correlate with intermolecular N-P distances as well as with bonding parameters obtained from AIM and SAPT analyses. Complexation increases (31)P chemical shieldings in complexes with binding energies greater than 19 kJ mol(-1). One-bond spin-spin coupling constants (1p)J(N-P) across the pnicogen interaction exhibit a quadratic dependence on the N-P distance for complexes H(2)XP:NXH(2), similar to the dependence of (2h)J(X-Y) on the X-Y distance for complexes with X-H···Y hydrogen bonds. However, when the mixed complexes H(2)XP:NX'H(2) are included, the curvature of the trendline changes and the good correlation between (1p)J(N-P) and the N-P distance is lost.

H2XP:OH2 Complexes: Hydrogen vs. Pnicogen Bonds

“…These angles vary between 161 and 168˝, indicating that the O-P-A arrangement approaches linearity. These values are consistent with the values of the P-P-A and N-P-A angles in the pnicogen-bonded complexes (H 2 XP) 2 [44] and H 2 XP:NXH 2 [45] . Table 5 also presents the NBO Olp→σ*P-A charge-transfer energies in these pnicogen-bonded complexes.…”

Mutual influence between anion–π and pnicogen bond interactions: The enhancement of P⋯N and P⋯O interactions by an anion–π bond

“…Thus, the electrostatic component of the A c c e p t e d M a n u s c r i p t 5 Pn-bond has been described in terms of the σ-hole concept. However, Scheiner [25,26] and Alkorta et al [27][28][29] have demonstrated that charge-transfer from the lone pair of the Lewis base to the σ* Pn-R orbital of the acid plays an essential role in the stabilization of Pn-bond complexes. Pn-bond interactions are relevant in biological systems.…”

Theoretical estimation of pnicogen bonds and hydrogen bonds in small heterocyclic complexes: Red-shifts and blue-shifts ruled by polarization effects

“…In other cases the charge transfer can outweigh the electrostatic contribution, as can be seen in the studies on charge-assisted hydrogen bonds [39]. In studies by Del Bene, Alkorta and others [40] many similarities were found between the PN-Bonds and HBonds in the NH 2 F•••PH 2 F•••HF trimer, for instance, the relationship between the strength of the P•••N interactions and P−F bond lengths [41].…”