Linear group 13 E[triple bond, length as m-dash]E triple bonds

Linear Group 13 E≡E Triple Bonds in E2 Li6 2

The triply bonded heavier main-group compounds have a textbook trans-bent geometry, in contrast to a familiar linear form found for the lightest analogues. Strikingly, the unexpected linear group 13 E≡E triple bonds were herein found in the D_4h -symmetry E₂ Li₆ ²⁺ clusters, and they possess a large barrier (>18.0 kcal/mol) towards the dissociation of Li⁺ . The perfectly surrounded Li₄ motifs and two linear coordinated Li atoms strongly suppress the increasing nonbonded electron density of heavier E atoms, making two degenerate π bonds and one multi-center σ bond in linear heavier main-group triple bonds. The surrounding Li₆ motifs not only creates an effective electronic structure to form a linear E≡E triple bond, but the resulting electrostatic interactions account for the highly stable global E₂ Li₆ ²⁺ clusters.

EE triple bonds (E = Group 13) promoted by charge transfer from alkali metals

Chemical bonding analysis shows that strong charge transfer arises from M4 (M = Li and Na) motifs to E2 (E = Group 13), further making an EE triple bond composed of two π bonds and one delocalized σ bond.