Facile heterolytic bond splitting of molecular chlorine upon reactions with Lewis bases: Comparison with ICl and I₂

Formation of molecular complexes and subsequent heterolytic halogen‐halogen bond splitting upon reactions of molecular Cl 2 with nitrogen‐containing Lewis bases (LB) are computationally studied at M06‐2X/def2‐TZVPD and for selected compounds at CCSD(T)/aug‐cc‐pvtz//CCSD/aug‐cc‐pvtz levels of theory. Obtained results are compared with data for ICl and I 2 molecules. Reaction pathways indicate, that in case of Cl 2 ∙LB complexes the activation energies for the heterolytic Cl‐Cl bond splitting are lower than the activation energies of the homolytic splitting of Cl 2 molecule into chlorine radicals. The heterolytic halogen splitting of molecular complexes of X 2 ∙Py with formation of [XPy 2 ] + … contact ion pairs in the gas phase is slightly endothermic in case of Cl 2 and I 2 , but slightly exothermic in the case of ICl. Formation of {[ClPy 2 ] + …} 2 dimers makes the overall process exothermic. Taking into account that polar solvents favor ionic species, generation of donor‐stabilized Cl + in the presence of the Lewis bases is expected to be favorable. Thus, in polar solvents the oxidation pathway via donor‐stabilized Cl + species is viable alternative to the homolytic Cl‐Cl bond breaking.