Pnicogen-Bonded
Anionic Complexes
Janet E. Del Bene
Ibon Alkorta
José Elguero
10.1021/jp502667k.s001
https://acs.figshare.com/articles/journal_contribution/Pnicogen_Bonded_Anionic_Complexes/2298895
Ab initio MP2/aug′-cc-pVTZ
calculations have been carried
out to investigate the pnicogen-bonded complexes H<sub>2</sub>YP:X<sup>–</sup>, for X,Y = Cl, NC, F, CCH, and CH<sub>3</sub>. Of
the 36 possible complexes, only 21 are unique equilibrium structures.
All substituents form (H<sub>2</sub>XPX)<sup>−</sup> complexes
with symmetric X–P–X bonds. The P–A ion–molecule
pnicogen bonds in these and some additional complexes have partial
covalent character, while some P–A′ covalent bonds have
partial ion–molecule character. A and A′ are the atoms
of X and Y, respectively, which are directly bonded to P. Complexes
with these types of bonds include the symmetric complexes (H<sub>2</sub>XPX)<sup>−</sup>, H<sub>2</sub>(CH<sub>3</sub>)P:F<sup>–</sup>, H<sub>2</sub>(CCH)P:F<sup>–</sup>, H<sub>2</sub>FP:NC<sup>–</sup>, H<sub>2</sub>FP:Cl<sup>–</sup>, H<sub>2</sub>FP:CN<sup>–</sup>, and H<sub>2</sub>(NC)P:Cl<sup>–</sup>. Charge transfer from A to the P–A′ σ* orbital
stabilizes H<sub>2</sub>YP:X<sup>–</sup> complexes and leads
to a reduction of the negative charge on X. For fixed X, the smallest
negative charge occurs in the symmetric complex. Then, for a given
X, the order of decreasing negative charge with respect to Y is CH<sub>3</sub> > CCH > CN (bonded through C) > F > NC (bonded
through N)
> Cl, which is also the order of decreasing P–A distance.
EOM-CCSD
spin–spin coupling constants <sup>1p</sup><i>J</i>(P–A) differentiate between shorter ion–molecule pnicogen
bonds with partial covalent character and longer P···A
ion–molecule pnicogen bonds. Similarly, coupling constants <sup>1</sup><i>J</i>(P–A′) differentiate between
longer covalent P–A′ bonds with partial ion–molecule
character and shorter P–A′ covalent bonds.
2014-05-08 00:00:00
CCH
pnicogen
charge
covalent character
bond
2FP
H 2XPX complexes
MP
NC
CH
CN
ion
H 2YP complexes