The heavy Carbene analogues SbH2 + and BiH2 +. Convergent quantum mechanical studies*

Abstract

In 2021 Olaru, Mebs, and Beckmann reported the synthesis of remarkable cationic carbene analogues P R 2 + and As R 2 + . This work followed the same group's synthesis of Sb R 2 + and Bi R 2 + . To better understand these important systems, Sb H 2 + and Bi H 2 + have been studied with high level ab initio quantum mechanical methods. Geometries were optimised with the CCSDT(Q) method with the cc-pwCVTZ-PP basis set using small core pseudopotentials. Fundamental vibrational frequencies were computed to provide theoretical predictions for future synthetic studies. Relative energies with respect to P n + + H 2 ( Pn = Sb , Bi ) were determined at the CCSDT/CBS level of theory via the Focal Point Analysis method, and anharmonic zero-point vibrational energy and higher order contributions were also computed. For Sb H 2 + , we obtained R = 1.697 Å and θ = 90.8 ∘ with S b + + H 2 → Sb H 2 + reaction enthalpy of ΔH = − 18.71 kcal mol − 1 . For Bi H 2 + , the analogous results were R = 1.774 Å, θ = 89.7 ∘ , and ΔH = − 7.64 kcal mol − 1 for B i + + H 2 → Bi H 2 + .