Thermochemical data for the decomposition of different heptahalides calculated at different computational levels using the def2-TZVPP basis set at the DFT and MP2 levels, and individual basis sets at the CCSD(T) level (see ESI). Energies are given in kJ mol⁻¹. A positive value implies an endothermic reaction.

Reaction	B3LYP-D3BJ	SCS-MP2	CCSD(T)
[F(ClF)3]− → [F(ClF)2]− + ClF	68.5	54.9	63.3
[Cl(Cl2)3]− → [Cl(Cl2)2]− + Cl2	41.8	32.522	—
[Cl(ClF)3]− → [Cl(ClF)2]− + ClF	62.6	34.7	53.1
[F(Cl2)3]− → [F(Cl2)2]− + Cl2	48.8	—	48.7