Facile heterolytic bond splitting of molecular chlorine upon reactions with Lewis bases: Comparison with ICl and I 2 .

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 ] + … X 3 - $$ {\mathrm{X}}_3^{-} $$ 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 ] + … Cl 3 - $$ {\mathrm{Cl}}_3^{-} $$ } 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.