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 $\mathrm{P}{\mathrm{R}}_2^{+}$ and $\mathrm{As}{\mathrm{R}}_2^{+}$. This work followed the same group's synthesis of $\mathrm{Sb}{\mathrm{R}}_2^{+}$ and $\mathrm{Bi}{\mathrm{R}}_2^{+}$. To better understand these important systems, $\mathrm{Sb}{\mathrm{H}}_2^{+}$ and $\mathrm{Bi}{\mathrm{H}}_2^{+}$ 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 $\mathrm{P}{\mathrm{n}}^{+}$ + ${\mathrm{H}}_2$ ($\mathrm{Pn}$ = $\mathrm{Sb}$, $\mathrm{Bi}$) 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 $\mathrm{Sb}{\mathrm{H}}_2^{+}$, we obtained R = 1.697 Å and $\theta ={90.8}^{\circ }$ with $\mathrm{S}{\mathrm{b}}^{+}+{\mathrm{H}}_2\to \mathrm{Sb}{\mathrm{H}}_2^{+}$ reaction enthalpy of $\mathrm{\Delta H}=-18.71\mathrm{kcal}{\mathrm{mol}}^{-1}$. For $\mathrm{Bi}{\mathrm{H}}_2^{+}$, the analogous results were R = 1.774 Å, $\theta ={89.7}^{\circ }$, and $\mathrm{\Delta H}=-7.64\mathrm{kcal}{\mathrm{mol}}^{-1}$ for $\mathrm{B}{\mathrm{i}}^{+}+{\mathrm{H}}_2\to \mathrm{Bi}{\mathrm{H}}_2^{+}$.

GRAPHICAL ABSTRACT

Keywords:

• Pnictogenium cations
• antimony
• bismuth
• ab initio
• CCSDT(Q)

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Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article was originally published with errors, which have now been corrected in the online version. Please see Correction (http://dx.doi.org/10.1080/00268976.2023.2278347)

Additional information

Funding

We acknowledge support from the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES) under Contract No. DE-SC0018412.