The concept of aromaticity was originally defined as a property of unsaturated, cyclic planar organic molecules like benzene, which gain stability by the inherent delocalization of 4n + 2 π-electrons over the ring atoms. Since then, π-aromaticity has been observed for a large variety of organic and inorganic non-metal compounds, yet, for molecules consisting only of metal atoms, it has remained restricted to systems with three to five atoms. Here, we present the straightforward synthesis of a metal 12-ring that exhibits 2π-aromaticity and has a ring current much stronger than that of benzene (6π) and equivalent to that of porphine (26π), despite these organic molecules having (much) larger numbers of π-electrons. Highly reducing reaction conditions allowed access to the heterometallic anion [Th@Bi₁₂]⁴⁻, with interstitial Th⁴⁺ stabilizing a Bi₁₂⁸⁻ moiety. Our results show that it is possible to design and generate substantial π-aromaticity in large metal rings, and we hope that such π-aromatic heavy-metal cycles will eventually find use in cluster-based reactions.

芳香性的概念最初被定义为不饱和环状平面有机分子（如苯）的一种特性，它们通过环原子上 4 n  + 2 π电子的固有离域获得稳定性。从那时起，已经观察到大量有机和无机非金属化合物的π芳香性，然而，对于仅由金属原子组成的分子，它仍然局限于具有三到五个原子的系统。在这里，我们介绍了金属 12 环的直接合成，该金属 12 环具有 2 π芳香性，环电流比苯 (6 π ) 强得多，相当于卟啉 (26 π ))，尽管这些有机分子具有（多）更多的π-电子。高度还原反应条件允许获得异金属阴离子 [Th@Bi ₁₂ ] ⁴⁻，间隙 Th ⁴⁺稳定 Bi ₁₂ ⁸⁻部分。我们的结果表明，可以在大金属环中设计和产生大量的π芳香性，我们希望这种π芳香重金属循环最终能在基于团簇的反应中找到用途。