Electronic structure-based design rules for noble gas complexes

The formation of noble gas compounds continues to challenge conventional chemical intuition and remains an active area of experimental and theoretical research. Here, we present a systematic computational study aimed at establishing a predictive criterion for their formation and thermodynamic stability, focusing primarily on non-inserted species. Inspired by Bartlett's seminal idea linking noble gas ionization energies to reactivity, we propose an extended model that also incorporates the electronic affinities of interacting fragments. Using Koopmans' theorem, we define a simple electronic descriptor, Δ₂ = ENgHOMO - EFragmentLUMO, which has a strong correlation with dissociation free energies computed at the CCSD(T)/def2-TZVP level for a diverse set of 192 diatomic and polyatomic complexes. Our results show that compounds with positive Δ₂ values are predicted to be thermodynamically stable, while systems with moderately negative Δ₂ values (-100 to -200 kcal mol^-1) may be metastable under low-temperature conditions. The descriptor remains applicable to noble gas interactions with polyatomic electron-deficient fragments, with stability trends rationalized via Hoffmann's isolobal principle. As a case study, the recently observed ArBO⁺ complex falls within the predicted stability window, validating the model. Overall, this work offers a simple and quantitative design rule for anticipating noble gas compound stability and provides a theoretical foundation to guide future experimental discoveries in noble gas chemistry.