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Boron as an Electron‐Pair Donor for B⋅⋅⋅Cl Halogen Bonds
Author(s) -
Alkorta Ibon,
Elguero José,
Del Bene Janet E.
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.201600435
Subject(s) - chemistry , lone pair , halogen , halogen bond , crystallography , covalent bond , natural bond orbital , atom (system on chip) , boron , stereochemistry , computational chemistry , molecule , density functional theory , alkyl , organic chemistry , computer science , embedded system
MP2/aug′‐cc‐pVTZ calculations were performed to investigate boron as an electron‐pair donor in halogen‐bonded complexes (CO) 2 (HB):ClX and (N 2 ) 2 (HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH 3 , and H. Equilibrium halogen‐bonded complexes with boron as the electron‐pair donor are found on all of the potential surfaces, except for (CO) 2 (HB):ClCH 3 and (N 2 ) 2 (HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO) 2 (HB):ClF, (CO) 2 (HB):ClCl, (N 2 ) 2 (HB):ClCl, and (N 2 ) 2 (HB):ClOH, which are stabilized by chlorine‐shared halogen bonds. These complexes have increased binding energies and shorter B−Cl distances. Charge transfer stabilizes all complexes and occurs from the B lone pair to the σ* Cl−A orbital of ClX, in which A is the atom of X directly bonded to Cl. A second reduced charge‐transfer interaction occurs in (CO) 2 (HB):ClX complexes from the Cl lone pair to the π* C≡O orbitals. Equation‐of‐motion coupled cluster singles and doubles (EOM‐CCSD) spin–spin coupling constants, 1 x J (B‐Cl), across the halogen bonds are also indicative of the changing nature of this bond. 1 x J (B‐Cl) values for both series of complexes are positive at long distances, increase as the distance decreases, and then decrease as the halogen bonds change from traditional to chlorine‐shared bonds, and begin to approach the values for the covalent bonds in the corresponding ions [(CO) 2 (HB)−Cl] + and [(N 2 ) 2 (HB)−Cl] + . Changes in 11 B chemical shieldings upon complexation correlate with changes in the charges on B.