Comparative Study of Dihydrogen, Tetrel, and Metal Bonds in Complexes of C3H4 Isomers with MH and MH2 (M = Li, Na, Be, and Mg)

Abstract In this manuscript, the interactions of metal hydrides, MH and MH2 (M = Li, Na, Be, and Mg), with the C3H4 isomers cyclopropane (CP) and propyne (P) were investigated using quantum chemical calculations at the MP2/aug-cc-pVTZ level of theory. The molecular electrostatic potential (MEP) results showed that each isomer exhibits distinct behavior and participates in different types of interactions with specific characteristics. The interaction patterns differ markedly between the MH and MH2 hydrides. For the MH monomers, Structure A is stabilized by a tetrel bond (TB), while Structure C is characterized by the simultaneous presence of dihydrogen bond and metal bond interactions (DHB–MB). In contrast, the corresponding MH2 monomers form TB complexes in Structure A but are stabilized exclusively by metal bond (MB) interactions in Structure C. By comparison, cyclopropane participates only in DHB complexes, giving rise to Structure B.The interaction energy (ΔEintCP) and thermodynamic calculations highlighted that the stability of the complexes follows the order C > B > A. They also indicated that complex formation is governed by an exothermic process. Moreover, ΔG was negative only for Structure C, indicating that the formation of these complexes is thermodynamically favorable under the specified gas-phase conditions at 298 K and 1 atm