An All-Metal Aromatic Sandwich Complex [Sb3Au3Sb3](3-)

• Published in: Journal of the American Chemical Society 2015-09, Vol.137 (34), p.10954-10957
• Main Authors: Pan, Fu-Xing, Li, Lei-Jiao, Wang, Ying-Jin, Guo, Jin-Chang, Zhai, Hua-Jin, Xu, Li, Sun, Zhong-Ming
• Format: Article
• Language: English
• ISSN: 1520-5126
• DOI: 10.1021/jacs.5b07730

A sandwich complex, as exemplified by ferrocene in the 1950s, usually refers to one metal center bound by two arene ligands. The subject has subsequently been extended to carbon-free aromatic ligands and multiple-metal-atom "monolayered" center, but not to an all-metal species. Here, we describe the synthesis of an unprecedented all-metal aromatic sandwich complex, [Sb3Au3Sb3](3-), which was isolated as K([2.2.2]crypt)(+) salt and identified by single-crystal X-ray diffraction. Quantum chemical calculations indicate that intramolecular electron transfers for the three metallic layers (Sb → Au donation and Sb ← Au back-donation) markedly redistribute the valence electrons from the cyclo-Sb3 ligands and Au3 interlayer to the Au-Sb bonds, which hold the complex together via σ bonding. Each cyclo-Sb3 possesses aromaticity with delocalized three-center three-electron (3c-3e) π bonds, which are essentially equivalent to a 3c-4e ππ* triplet system, following the reversed 4n Hückel rule for aromaticity in a triplet state.