A Stable Cyclic (R2SnAu)3 Anion Having In‐Plane σ‐Möbius Aromaticity

• Published in: Angewandte Chemie International Edition 2020-01, Vol.59 (5), p.1980-1984
• Main Authors: Wang, Liliang, Xu, Jian, Kira, Mitsuo, Yan, Liping, Xiao, Xu‐Qiong, Li, Zhifang
• Format: Article
• Language: English
• Subjects: Anions; Aromaticity; Crystallography; Gold; gold complexes; low-valent compounds; NMR; Nuclear magnetic resonance; Perturbation methods; stannylenes; Tin; σ-Hückel aromaticity; σ-Möbius aromaticity
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201910731

A cyclic (R2SnAu)3 anion (3−, R2Sn=2,2,5,5‐tetrakis(trimethylsilyl)‐1‐stannacyclopentane‐1,1‐diyl) has been synthesized as a stable blue salt with K+(THF)6 through the reaction of stable dialkylstannylene 1 with R′3PAuCl (R′=Et, Ph) followed by the reduction with KC8. Crystallographic and NMR analysis shows that the six‐membered (SnAu)3 ring of 3− is planar and highly symmetric with an equal distance of six Au−Sn bonds. A UV/Vis spectrum of 3− in hexane reveals an intense absorption maximum at 598 nm. While cyclic Au3− with four valence electrons is known as unstable anti‐aromatic anion, 3− with three divalent tin ligands is stable σ aromatic anion with an unprecedented Möbius orbital array as predicted by the perturbation MO and CCSD analysis of 3−. A cyclic (R2SnAu)3 anion has been synthesized as a stable blue salt with K+(THF)6 by reaction of a dialkylstannylene with R′3PAuCl (R′=Et, Ph) and reduction with KC8. The six‐membered (SnAu)3 ring is planar and highly symmetric. Whereas cyclic Au3− with four valence electrons is an unstable anti‐aromatic anion, the (R2SnAu)3 anion with three divalent tin ligands is a stable σ aromatic anion with an unprecedented Möbius orbital array.