Comparative Study\nof Neutral and Cationic Sn<sub>2</sub>H<sub>2</sub>: Toward Laboratory\nDetection of the Cation

Group 14 M<sub>2</sub>H<sub>2</sub> isomers (M = Si,\nGe, Sn, and\nPb) have attracted interest due to their radically differing electronic\nstructures from acetylene. To better understand the Sn–H interactions\nof the neutral and cationic Sn<sub>2</sub>H<sub>2</sub> structures,\nwe present the most rigorous study of these systems to date. CCSD(T)/cc-pwCVTZ\nharmonic frequencies are presented as the first predictions for the\nneutral and cationic species to date. CCSDT(Q)/CBS relative energies\nare reported using the focal point approach, confirming the butterfly\nisomer as the global minimum on the potential energy surface for both\nthe neutral and cationic species. In all, there exist 7 minima and\n15 transition states. NBO analysis is also performed to elucidate\nthe changes in bond order going from neutral to cation across all\nisomers of Sn<sub>2</sub>H<sub>2</sub>. Our results provide insights\ninto the important Sn–H interaction and provide guidance for\nfuture work that may detect Sn2H2+ in the laboratory for the first time.