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Yes—but not as a silicon copy of benzene. In a 2010 Science report, chemists described a green, tricyclic silicon compound with the formula Si6R6 and argued that its central four-membered ring has an unusual form of aromaticity. Its framework is chairlike rather than a flat six-atom ring, and the authors proposed the name “dismutational aromaticity” for the electronic pattern.
What did “silicon goes aromatic” mean?
The phrase refers to a specific molecule reported by Kai Abersfelder, Andrew J. P. White, Henry S. Rzepa, and David Scheschkewitz in Science on 29 January 2010. Their compound was an intensely green isomer of hexasilabenzene, with the formula Si6R6. Here, R is 2,4,6-triisopropylphenyl, a bulky organic substituent.
Calling it an isomer means it has the same overall formula as the targeted hexasilabenzene structure but a different arrangement of atoms and bonds. The solid-state structure is tricyclic: its six silicon atoms form a framework of three rings, and different silicon atoms carry two, one, or no substituents outside that framework. It is not a simple six-silicon ring. (Abersfelder et al., Science, 2010; Chemical & Engineering News, 1 February 2010)
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How is it different from benzene?
Benzene is commonly introduced as a planar ring of six carbon atoms whose six pi electrons are delocalized around the ring. The silicon compound has a different architecture and a different proposed explanation for its aromatic character.
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| Feature | Benzene | 2010 silicon compound |
|---|---|---|
| Framework | Planar six-carbon ring | Tricyclic, chairlike silicon framework |
| Where the proposed cyclic delocalization occurs | Around the six-membered carbon ring | Across the central four-membered ring |
| Electrons in the proposed pattern | Six pi electrons in the familiar introductory model | Six mobile electrons with pi, sigma, and non-bonding character, according to the authors’ analysis |
The contemporary description of the silicon structure as chairlike is important: a drawing that presents it as a flat Si6 hexagon would give the wrong impression. The compound was made by coupling cyclotrisilane units bearing bulky substituents, not by simply replacing each carbon atom in a benzene ring with silicon. (Chemical & Engineering News, 1 February 2010)
Why did the authors call it “dismutational aromaticity”?
Aromaticity is an interpretation of a molecule’s electronic structure, not merely a label for a ring-shaped structure. In this case, theoretical analysis identified cyclic delocalization involving six mobile electrons across the central four-membered ring. Because the proposed pattern includes pi, sigma, and non-bonding electron character in an unusual framework, the authors proposed “dismutational aromaticity” as its name.
The term is the authors’ proposal, not a claim that the molecule is electronically identical to benzene or that every use of “aromatic” refers to one settled definition. In the paper’s abstract, they describe the alternative as potentially applicable in principle to many Hückel-aromatic species. (Abersfelder et al., Science, 2010)
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What did the NMR and ring-current analysis show?
The 2010 paper reported solution-state silicon-29 NMR shifts ranging from +125 to −90 ppm. The authors associated this unusually broad, inhomogeneous distribution with dismutation of formal oxidation numbers. These shifts are evidence about the distinct electronic environments of the silicon atoms; they are not, by themselves, a demonstration that the molecule behaves like benzene.
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A follow-up study by Raphael J. F. Berger, Henry S. Rzepa, and David Scheschkewitz, first published on 16 November 2010, examined the molecule’s magnetic response. Its authors described “rollercoaster ring currents” and a topology without a paramagnetic vortex at the center of the ring. That analysis offers a more specialized picture of the magnetic evidence; it does not erase the molecule’s structural difference from benzene. (Berger, Rzepa, and Scheschkewitz, Angewandte Chemie International Edition, 2010)
Was the compound an electronics material?
No practical optical-electronics use was demonstrated in the reporting. Contemporary coverage raised analogous silicon compounds as a possible future direction, but that was speculation about potential relevance, not an established application or a working device. The result’s significance was the unusual molecular structure and the proposed electronic interpretation. (Chemical & Engineering News, 1 February 2010)
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Did silicon aromaticity research end there?
No. Work on aromatic silicon compounds continued, but later molecules should not be confused with the 2010 Si6R6 isomer. For example, a 2023 Journal of the American Chemical Society paper reported neutral silicon four-membered rings with two-pi-electron aromaticity and distinct structures and chemistry. It is a later development in the broader field, not a revised identity for the earlier tricyclic compound. (2023 Journal of the American Chemical Society paper)
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