The Isomers of the Acetylene Derivatives C 2 Li 4 : Transferable Structural Units in Hyperlithiated Compounds

C 2 Li 4 is an acetylene and not an ethylene derivative , despite its stoichiometry. All the isomers correspond to minima on the potential energy surface of C 2 Li 4 . Ab initio calculations established the occurrence of Li   2 + , Li   3 + , and Li   4 2+units, characteristic for per‐ and hyperlithiated molecules, and showed that structure 1 lies at the global energy minimum.