Characterisation of a pre-reactive intermediate in gas-phase mixtures of fluorine and ammonia: the rotational spectrum of the H3N…F2 complex

Theoretical Insights into the Nature of Halogen Bonding in Prereactive Complexes

“…The present theoretical investigation is focused upon the halogen bonding between a dihalogen XY and ammonia as the Lewis base. The experimentally derived angular geometries of H 3 N⋅⋅⋅XY all show a C 3 v structure,17–22 and this directionality conforms with what might be expected from the σ-hole concept; the optimal halogen bond should form such that R-X⋅⋅⋅N is linear to maximise the interaction between the area of electron depletion and the nitrogen lone pair.…”

“…Comparison with the conventional CCSD(T)/aug-cc-pVTZ results of Karpfen indicates that the lower-level calculations produce intermolecular bond lengths that are too long by up to 0.06 Å,[37] and that MP2/aug-cc-pVTZ fortuitously produces geometries closer to CCSD(T)-F12b/VTZ-F12 than CCSD(T)/aug-cc-pVTZ does. The experimental estimates of the intermolecular bond lengths (2.708 Å for H 3 N⋅⋅⋅F 2 ,[17] 2.73 Å for H 3 N⋅⋅⋅Cl 2 ,[19] and 2.37 Å for H 3 N⋅⋅⋅ClF)[18] were obtained under the approximation that the monomer geometries do not change under complexation and are not directly comparable to the theoretical equilibrium geometry results in Figure 1, but it can be seen that the trends are much the same; the H 3 N⋅⋅⋅F 2 intermolecular distance is only slightly shorter than that in H 3 N⋅⋅⋅Cl 2 , with H 3 N⋅⋅⋅ClF shorter by approximately 0.36 Å.…”

“…Using the famous Mulliken notation,[23] this small amount of charge transfer would be termed an “outer complex” and it may be expected that the intermolecular interaction is weak. The experimental intermolecular stretching force constants ( k σ ) have also been determined for a number of H 3 N⋅⋅⋅XY complexes 17–22…”

Comparison between standard and counterpoise-corrected optimization using some hydrogen and halogen bonded systems

“…The B Á Á Á X bond lengths have previously been determined by experimental techniques for some dimers [20][21][22][23][24][25][26][27][28][29][30][31][32] Some optimized structures are minimum stationary points at the standard level whereas they are maximum stationary points at the CP-corrected level, and vice versa. For example, linear structures of N 2 Á Á Á HCl and N 2 Á Á Á HBr are ground states by the CP-corrected method and, with negative vibrational frequencies, are transition states by the standard method.…”

Präreaktive Komplexe der Dihalogene XY mit Lewis-Basen B in der Gasphase: eine systematische Studie der Halogen-Analoga B⋅⋅⋅XY der Wasserstoffbrückenbindungen B⋅⋅⋅HX

“…Diese Reihenfolge trifft auch bei B´´´F 2 -Komplexen mit B HCN, [63] H 2 S [64] und NH 3 [65] zu, wobei diese Komplexe durch eine extrem schwache Wechselwirkung gekennzeichnet sind. Zweitens gilt für k s bei kon-stantem XY F 2`C l 2`B rCl`ClF.…”