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Using (FH) 2 and (FH) 3 to Bridge the σ‐Hole and the Lone Pair at P in Complexes with H 2 XP, for X=CH 3 , OH, H, CCH, F, Cl, NC, and CN
Author(s) -
Del Bene Janet E.,
Alkorta Ibon,
Elguero José
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600048
Subject(s) - lone pair , crystallography , chemistry , antibonding molecular orbital , hydrogen bond , molecule , acceptor , ternary operation , intermolecular force , ab initio , binding energy , stereochemistry , atomic orbital , atomic physics , physics , organic chemistry , quantum mechanics , computer science , programming language , condensed matter physics , electron
Ab initio MP2/aug′‐cc‐pVTZ calculations are used to investigate the binary complexes H 2 XP:HF, the ternary complexes H 2 XP:(FH) 2 , and the quaternary complexes H 2 XP:(FH) 3 , for X=CH 3 , OH, H, CCH, F, Cl, NC, and CN. Hydrogen‐bonded (HB) binary complexes are formed between all H 2 XP molecules and FH, but only H 2 FP, H 2 ClP, and H 2 (NC)P form pnicogen‐bonded (ZB) complexes with FH. Ternary complexes with (FH) 2 are stabilized by F−H⋅⋅⋅P and F−H⋅⋅⋅F hydrogen bonds and F⋅⋅⋅P pnicogen bonds, except for H 2 (CH 3 )P:(FH) 2 and H 3 P:(FH) 2 , which do not have pnicogen bonds. All quaternary complexes H 2 XP:(FH) 3 are stabilized by both F−H⋅⋅⋅P and F−H⋅⋅⋅F hydrogen bonds and P⋅⋅⋅F pnicogen bonds. Thus, (FH) 2 with two exceptions, and (FH) 3 can bridge the σ‐hole and the lone pair at P in these complexes. The binding energies of H 2 XP:(FH) 3 complexes are significantly greater than the binding energies of H 2 XP:(FH) 2 complexes, and nonadditivities are synergistic in both series. Charge transfer occurs across all intermolecular bonds from the lone‐pair donor atom to an antibonding σ* orbital of the acceptor molecule, and stabilizes these complexes. Charge‐transfer energies across the pnicogen bond correlate with the intermolecular P−F distance, while charge‐transfer energies across F−H⋅⋅⋅P and F−H⋅⋅⋅F hydrogen bonds correlate with the distance between the lone‐pair donor atom and the hydrogen‐bonded H atom. In binary and quaternary complexes, charge transfer energies also correlate with the distance between the electron‐donor atom and the hydrogen‐bonded F atom. EOM‐CCSD spin‐spin coupling constants 2h J (F–P) across F−H⋅⋅⋅P hydrogen bonds, and 1p J (P–F) across pnicogen bonds in binary, ternary, and quaternary complexes exhibit strong correlations with the corresponding intermolecular distances. Hydrogen bonds are better transmitters of F–P coupling data than pnicogen bonds, despite the longer F⋅⋅⋅P distances in F−H⋅⋅⋅P hydrogen bonds compared to P⋅⋅⋅F pnicogen bonds. There is a correlation between the two bond coupling constants 2h J (F–F) in the quaternary complexes and the corresponding intermolecular distances, but not in the ternary complexes, a reflection of the distorted geometries of the bridging dimers in ternary complexes.