Comparative Study of Neutral and Cationic Sn₂H₂: Toward Laboratory Detection of the Cation

Group 14 M₂H₂ isomers (M = Si, Ge, Sn, and Pb) have attracted interest due to their radically differing electronic structures from acetylene. To better understand the Sn-H interactions of the neutral and cationic Sn₂H₂ structures, we present the most rigorous study of these systems to date. CCSD(T)/cc-pwCVTZ harmonic frequencies are presented as the first predictions for the neutral and cationic species to date. CCSDT(Q)/CBS relative energies are reported using the focal point approach, confirming the butterfly isomer as the global minimum on the potential energy surface for both the neutral and cationic species. In all, there exist 7 minima and 15 transition states. NBO analysis is also performed to elucidate the changes in bond order going from neutral to cation across all isomers of Sn₂H₂. Our results provide insights into the important Sn-H interaction and provide guidance for future work that may detect <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:msub><mml:mstyle><mml:mrow><mml:mi>S</mml:mi><mml:mi>n</mml:mi></mml:mrow></mml:mstyle><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math> in the laboratory for the first time.