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

In 2021 Olaru, Mebs, and Beckmann reported the synthesis of remarkable cationic carbene analogues $ \mathrm{PR_2^+} $ P R 2 + and $ \mathrm{AsR_2^+} $ As R 2 + . This work followed the same group's synthesis of $ \mathrm{SbR_2^+} $ Sb R 2 + and $ \mathrm{BiR_2^+} $ Bi R 2 + . To better understand these important systems, $ \mathrm{SbH_2^+} $ Sb H 2 + and $ \mathrm{BiH_2^+} $ 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 $ \mathrm{Pn^+} $ P n + + $ \mathrm{H_2} $ H 2 ( $ \mathrm{Pn} $ Pn = $ \mathrm{Sb} $ Sb , $ \mathrm{Bi} $ 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 $ \mathrm{SbH_2^+} $ Sb H 2 + , we obtained R = 1.697 Å and $ \theta =90.8^{\circ } $ θ = 90.8 ∘ with $ \mathrm{Sb^+ + H_2 \rightarrow SbH_2^+} $ S b + + H 2 → Sb H 2 + reaction enthalpy of $ \Delta H = -18.71\,{\rm kcal}\ {\rm mol}^{-1} $ ΔH = − 18.71 kcal mol − 1 . For $ \mathrm{BiH_2^+} $ Bi H 2 + , the analogous results were R = 1.774 Å, $ \theta =89.7^{\circ } $ θ = 89.7 ∘ , and $ \Delta H = -7.64\,{\rm kcal}\,{\rm mol}^{-1} $ ΔH = − 7.64 kcal mol − 1 for $ \mathrm{Bi^+ + H_2 \rightarrow BiH_2^+} $ B i + + H 2 → Bi H 2 + . [ABSTRACT FROM AUTHOR]