Capturing aromatic Cr₅ pentagons in large main-group molecular cages

Chromium chemistry is attractive to researchers due to its interesting structural arrangements and unusual Cr–Cr bonding interactions. However, the exploration of polymeric Cr_n (n > 3) clusters is challenging because of the difficulty in achieving precise matching between the metal cores and ligands. To the best of our knowledge, planar Cr_n configurations beyond the Cr₃ triangle have not been identified. In this study, we successfully isolated and characterized a Cr₅ cluster using the Zintl ion synthesis route. This cluster exists within the ternary anion [Cr₅Sn₂Sb₂₀]⁴⁻ and the nanoscale dimer fusion anion [(Cr₅)₂Sn₆Sb₃₀]⁶⁻. Furthermore, we elucidated the aromatic properties of the Cr₅Sn₂ subunits through theoretical computational analysis, this aromaticity substantially enhancing the intrinsic stability of these Cr₅ cluster species. (Figure presented.)