Boron as an Electron‐Pair Donor for B⋅⋅⋅Cl Halogen Bonds

Abstract

MP2/aug'-cc-pVTZ calculations were performed to investigate boron as an electron-pair donor in halogen-bonded complexes (CO) (HB):ClX and (N ) (HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH , and H. Equilibrium halogen-bonded complexes with boron as the electron-pair donor are found on all of the potential surfaces, except for (CO) (HB):ClCH and (N ) (HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO) (HB):ClF, (CO) (HB):ClCl, (N ) (HB):ClCl, and (N ) (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) (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, J(B-Cl), across the halogen bonds are also indicative of the changing nature of this bond. 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) (HB)-Cl] and [(N ) (HB)-Cl] . Changes in B chemical shieldings upon complexation correlate with changes in the charges on B.

One‐Electron Bonds in Frustrated Lewis Pair TPB Ligands: Boron Behaving as a Lewis Base

“…Indeed, the plot of the natural charges for the three atoms involved in the path (Figure S3) shows that the A⋅⋅⋅M⋅⋅⋅Y atoms are polarized following a +δ/−δ/+δ (P) or a −δ/+δ/−δ (N) pattern. These results are in consonance with recent works regarding a less‐common behavior of trivalent B as a donor, such as in B⋅⋅⋅Cl halogen bonds and B 2 H 4 complexes …”

One‐Electron Bonds in Frustrated Lewis Pair TPB Ligands: Boron Behaving as a Lewis Base

“…These interactions are directly related with the ability of forming one-electron B/ Al···Cu sigma bonds,inwhich Band Al behave as Lewis bases rather than as Lewis acids.I ndeed, the plot of the natural charges for the three atoms involved in the path ( Figure S3) shows that the A···M···Y atoms are polarized following a + d/ Àd/ + d (P) or a Àd/ + d/Àd (N) pattern. These results are in consonance with recent works regarding al ess-common behavior of trivalent Ba sadonor, such as in B···Cl halogen bonds [24] and B 2 H 4 complexes. [25]…”

A Continuum from Halogen Bonds to Covalent Bonds: Where Do λ3 Iodanes Fit?

“…XB is a non-covalent interaction between an electrophilic halogen (X) and a nucleophile with a lone pair (lp(A)) of donating electrons [42,43]. For the remainder of this work, we will express lone pairs as (lp).The nucleophile/halogen acceptor (A), donates electrons to the antibonding (σ*(XY)) orbital of the halogen donor (Y) [48,49]. XB is also known to have an X-A distance that is shorter than the sum of the vdW radii with Y-X-A angles close to 180 degrees [35,41,50,51].…”