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

Abstract

In the framework of SMD approach a systematic computational study of structural, electronic and thermodynamic properties of molecular complexes of Cl₂, ICl and I₂ with series of N-containing Lewis bases in solvents of different polarity was carried out. Results indicate that molecular complexes of Cl₂ 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 Cl₂ 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 OEt₂, ε = 4.24) should not be neglected and single point solvation energy computations on gas phase optimized geometries are not reliable for such systems.