Does φ-Aromaticity exist in prismatic {Bi6}-based clusters?

Abstract

In a recent paper (Peerless et al. Nat. Chem. 15, 347-356, (2023)), the authors isolated the heterometallic cluster containing at its heart the prismatic {Bi6}-based cluster. To explain its exceptionally high abundance and selective formation tendency (as compared to other Zintl clusters) as well as the unusual magnetic-response properties, the authors introduced the so-called phi-aromaticity. Here, we show that introducing a new type of aromaticity in this case is unjustified and misleading.

[K2(Bi@Pd12@Bi20)]4–: An Endohedral Inorganic Fullerene with Spherical Aromaticity

“…42 The existence of ϕ-aromaticity in the triangular-prismatic {Bi 6 } cluster has been extensively discussed by chemists. 43,44 However, the synthesis of polybismuth clusters has historically been limited compared with other lighter element congeners. While Zintl detected the potential existence of the Bi 7 3− anion through potentiometric titration experiments in 1932, Bi 2 2− and Bi 4 2− were the largest known bismuth anion clusters for an extended period.…”

“…Polybismuth clusters have attracted considerable attention due to their aromatic behavior and magnetic properties. − One striking example is cluster [Th@Bi 12 ] 4– , which exhibits 2π electrons delocalized over the nonplanar {Bi 12 } and displays a ring current as strong as that in porphine, making it an all-metal aromatic compound . The existence of ϕ-aromaticity in the triangular-prismatic {Bi 6 } cluster has been extensively discussed by chemists. , However, the synthesis of polybismuth clusters has historically been limited compared with other lighter element congeners. While Zintl detected the potential existence of the Bi 7 3– anion through potentiometric titration experiments in 1932, Bi 2 2– and Bi 4 2– were the largest known bismuth anion clusters for an extended period. − It was not until 2014 that Dehnen and co-workers successfully isolated Bi 11 3– from the solution phase, overcoming this limitation .…”