**4. Conclusion**

This computational study uses density functional theory to determine the thermodynamic stability of {η<sup>2</sup> -(X@Cn)}ML2 complexes (M = Pt, Pd; X = F<sup>−</sup> , 0, Li+ and n = 60, 70, 76, 84, 90 and 96). The calculations show the reaction is more stable when the Li<sup>+</sup> ion is encapsulated within Cn but the complex becomes unstable if there is a F− ion. Basic EDA shows that there is an increase in the interaction between the metal fragment and Cn if there is an encapsulated Li+ ion but F− ion has the opposite effect.

The advanced EDA results show that π back-bonding is crucial to thermodynamic stability and that thermodynamic stability is increased by the presence of a Li<sup>+</sup> ion but the presence of a F<sup>−</sup> ion has the opposite effect. These computations also show that a platinum center results in stronger π back-bonding than a palladium center and that there is no linear relationship between cage size and π back-bonding.
