First examples of stable transition metal complexes of an all-metal antiaromatic molecule (Al$_4$Li$_4$)

Abstract

We propose new methodologies for stabilizing all-metal antiaromatic clusters like: Al$_{4}$Li$_{4}$. We demonstrate that these all-metal species can be stabilized by complexation with 3d-transition metals very similar to its organic counterpart, C$_4$H$_4$. Complexation to transition metal ions reduce the frontier orbital energies and introduces aromaticity. We consider a series of such complexes [$η$$^4$(Al$_4$Li$_4$)-Fe(CO)$_3$, $η$$^2$$σ$$^2$(Al$_4$Li$_4$)-Ni and (Al$_{4}$Li$_{4}$)$_{2}$Ni] and make a comparison between the all-metal species and the organometallic compounds to prove conclusively our theory. Fragmentation energy analysis as well as NICS support similar mechanism of complexation induced stability in these all-metal molecules.