Complexes H₂CO:PXH₂and HCO₂H : PXH₂for X=NC, F, Cl, CN, OH, CCH, CH₃, and H: Pnicogen Bonds and Hydrogen Bonds

Abstract

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate H 2 CO : PXH 2 pnicogen-bonded complexes and HCO 2 H : PXH 2 complexes that are stabilized by pnicogen bonds and hydrogen bonds, with X = NC, F, Cl, CN, OH, CCH, CH 3 , and H. The binding energies of these complexes exhibit a secondorder dependence on the OÀ P distance. DFT-SAPT binding energies correlate linearly with MP2 binding energies. The HCO 2 H : PXH 2 complexes are stabilized by both a pnicogen bond and a hydrogen bond, resulting in greater binding energies for the HCO 2 H : PXH 2 complexes compared to H 2 CO : PXH 2 . Neither the OÀ P distance across the pnicogen bond nor the OÀ P distance across the hydrogen bond correlates with the binding energies of these complexes. The nonlinearity of the hydrogen bonds suggests that they are relatively weak bonds, except for complexes in which the substituent X is either CH 3 or H. The pnicogen bond is the more important stabilizing interaction in the HCO 2 H : PXH 2 complexes except when the substituent X is a more electropositive group. EOM-CCSD spin-spin coupling constants 1p J(OÀ P) across pnicogen bonds in H 2 CO:PXH 2 and HCO 2 H : PXH 2 complexes increase as the OÀ P distance decreases, and exhibit a second order dependence on that distance. There is no correlation between 2h J(OÀ P) and the OÀ P distance across the hydrogen bond in the HCO 2 H : PXH 2 complexes. 2h J(OÀ P) coupling constants for complexes with X = CH 3 and H have much greater absolute values than anticipated from their OÀ P distances.[a] Dr.

IR and NMR properties of N-base:PH2F:BeX2 ternary and corresponding binary complexes stabilised by pnicogen and beryllium bonds

“…In previous studies we have demonstrated that spin-spin coupling constants across hydrogen [31], halogen [32], chalcogen [33], pnicogen [34], and tetrel bonds [35] provide a fingerprint of the nature of the intermolecular bond in a related series of complexes. These coupling constants increase in absolute value as the intermolecular distance decreases in complexes with traditional intermolecular bonds, may reach a maximum as the bond length decreases and the bonds become atomshared bonds, and then further decreases as atom transfer occurs.…”

Properties and Stabilities of Cyclic and Open Chains of Halogen Bonds

“…The latter are characterized by the replacement of the bridging proton by any of a wide assortment of other atoms, most more electronegative than H. These interactions are commonly categorized in reference to the family of elements from which this replacement bridging atom is drawn. The chalcogen bond, − for example, makes use of S, Se, and Te, while the involvement of P, As, or Sb leads to the designation as a pnicogen bond. − …”

On the Ability of Nitrogen to Serve as an Electron Acceptor in a Pnicogen Bond

“…A close cousin of the halogen bond is the pnicogen bond in which the bridging atom is drawn from Group 15 of the periodic table. − These bonds can be quite strong, ranging well up above 10 kcal/mol. As in most interactions of this sort, the binding strength increases as one progresses down the column of the periodic table, again for reasons of diminishing electronegativity and rising polarizability.…”