The Influence of the Solvation on the Bonding of Molecular Complexes of Diatomic Halogens With Nitrogen-Containing Donors and Their Stability With Respect to the Heterolytic Halogen-Halogen Bond Splitting.

In the framework of SMD approach a systematic computational study of structural, electronic and thermodynamic properties of molecular complexes of Cl, ICl and I with series of N-containing Lewis bases in solvents of different polarity was carried out. Results indicate that molecular complexes of Cl with strong and medium-strong LB undergo spontaneous ionization in the acetonitrile solution. The increase of the solvent polarity can change the nature of interaction in X'XLB systems from molecular X'X ← LB donor-acceptor complexes to 3-center 4-electron bound X'→X ← LB in solvents of medium polarity and to the contact ion pairs X'→[XLB] in polar solvents. Thus, the controlled generation of cationic [LB∙X] species is possible by varying the nature of LB, varying the nature of the solvent, and varying the nature of the halogen X. Molecular Cl has the greatest tendency to form ionic species in polar solvents. Spontaneous ionization of molecular nσ complexes of chlorine with strong LB in medium-polar solvents (starting from OEt, ε = 4.24) should not be neglected and single point solvation energy computations on gas phase optimized geometries are not reliable for such systems.