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Buzsáki D, Kovács MB, Hümpfner E, Harcsa-Pintér Z, Kelemen Z. Conjugation between 3D and 2D aromaticity: does it really exist? The case of carborane-fused heterocycles. Chem Sci 2022; 13:11388-11393. [PMID: 36320586 PMCID: PMC9533420 DOI: 10.1039/d2sc03511a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 09/02/2022] [Indexed: 11/21/2022] Open
Abstract
Although several synthesized icosahedral carborane fused 2D π-ring systems are known, and even considerable conjugation has been noted between them in some cases, the phenomenon itself is not fully understood. Based on the results of our computational study, it can be concluded that the 2D aromatic character of the fused (exo) five-membered ring is low, even in cases where significant conjugation was proposed in previous studies. Moreover, the carborane moiety constricts the bonding properties of the exo ring, thus prohibiting or promoting different Lewis resonance structures. These results will shed further light on the design and electronic modulation of new carborane-based materials. We have demonstrated that carborane fused heterocycles can definitely be considered as non-2D aromatic compounds; therefore, their aromatic character was significantly overestimated in earlier studies.![]()
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Affiliation(s)
- Dániel Buzsáki
- MTA-BME Computation Driven Chemistry Group, Műegyetem rkp 3., H-1111 Budapest, Hungary
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rkp 3., H-1111 Budapest, Hungary
| | - Máté Barnabás Kovács
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rkp 3., H-1111 Budapest, Hungary
| | - Evelyn Hümpfner
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rkp 3., H-1111 Budapest, Hungary
| | - Zsófia Harcsa-Pintér
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rkp 3., H-1111 Budapest, Hungary
| | - Zsolt Kelemen
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rkp 3., H-1111 Budapest, Hungary
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2
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Ito S, Ishii Y, Kuwabara T. Inorganic salt-assisted assembly of anionic π-conjugated rings enabling 7Li NMR-based evaluation of antiaromaticity. Dalton Trans 2022; 51:16397-16402. [DOI: 10.1039/d2dt02649j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A cluster composed of three dilithium dibenzosilepinides and two Li2O molecules showed downfield shifted 7Li{1H} NMR signals (δ = 6.3, 4.4) due to the paratropic ring currents of the dianionic dibenzosilepins.
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Affiliation(s)
- Shotaro Ito
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan
| | - Youichi Ishii
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo, 112-8551, Japan
| | - Takuya Kuwabara
- Department of Chemistry and Biochemistry, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan
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3
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Reinhold CRW, Schmidtmann M, Tumanskii B, Müller T. Radicals and Anions of Siloles and Germoles. Chemistry 2021; 27:12063-12068. [PMID: 33978965 PMCID: PMC8453960 DOI: 10.1002/chem.202101415] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Indexed: 11/27/2022]
Abstract
The synthesis of persistent sila- and germacyclopentadienyl (silolyl- and germolyl-) radicals by careful stoichiometric reduction of the corresponding halides with potassium is reported. The radicals were characterized by EPR spectroscopy and trapping reactions. The reduction of tris(trimethylsilyl)silyl-substituted halides was successful while smaller substituents (i. e., t-Butyl, Ph) gave the corresponding dimers. The EPR spectroscopic parameter of the synthesized tetrolyl radicals indicate only small spin delocalization to the butadiene unit due to cross-hyperconjugation. Silolyl- and germolyl anions are unavoidable byproducts and are isolated in the form of their potassium salts and characterized by X-ray crystallography. The comparison of the molecular structures of two closely related potassium silolides provided an example for different coordination of the potassium cation to the silolyl anion (η1 vs. η5 coordination) that triggers the switch between delocalized and localized states.
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Affiliation(s)
- Crispin R. W. Reinhold
- Institute of ChemistryCarl von Ossietzky University OldenburgCarl von Ossietzky-Str. 9–1126129OldenburgGermany, European Union
| | - Marc Schmidtmann
- Institute of ChemistryCarl von Ossietzky University OldenburgCarl von Ossietzky-Str. 9–1126129OldenburgGermany, European Union
| | - Boris Tumanskii
- Schulich Faculty of ChemistryTechnion-Israel Institute of TechnologyHaifa32000Israel
| | - Thomas Müller
- Institute of ChemistryCarl von Ossietzky University OldenburgCarl von Ossietzky-Str. 9–1126129OldenburgGermany, European Union
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Ota K, Kinjo R. Heavier element-containing aromatics of [4 n+2]-electron systems. Chem Soc Rev 2021; 50:10594-10673. [PMID: 34369490 DOI: 10.1039/d0cs01354d] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
While the implication of the aromaticity concept has been dramatically expanded to date since its emergence in 1865, the classical [4n+2]/4n-electron counting protocol still plays an essential role in evaluating the aromatic nature of compounds. Over the last few decades, a variety of heavier heterocycles featuring the formal [4n+2] π-electron arrangements have been developed, which allows for assessing their aromatic nature. In this review, we present recent developments of the [4n+2]-electron systems of heavier heterocycles involving group 13-15 elements. The synthesis, spectroscopic data, structural parameters, computational data, and reactivity are introduced.
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Affiliation(s)
- Kei Ota
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Link 21, Singapore 637371, Singapore
| | - Rei Kinjo
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Nanyang Link 21, Singapore 637371, Singapore
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Affiliation(s)
- Soumava Santra
- Department of ChemistryLovelyProfessional University NH-41, Phagwara Punjab 144411 India
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Ito S, Kuwabara T, Ishii Y. A Tin Analogue of the Cycloheptatrienyl Anion: Synthesis, Structure, and Further Reduction to Form a Dianionic Species. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shotaro Ito
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Takuya Kuwabara
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
| | - Youichi Ishii
- Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27, Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
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Hong JH. Synthesis of 1,1'-Bis(1-Methyl/Chloro-2,3,4,5-Tetraphenyl-1-Silacyclopentadienyl) [Ph 4C 4Si(Me/Cl)-(Me/Cl)SiC 4Ph 4] from Silole Anion [MeSiC 4Ph 4] -•[Li + or Na +] and Silole Dianion [SiC 4Ph 4] 2-•2[Li +]; Oxidative Coupling of Silole Anion [MeSiC 4Ph 4] -•[Li + or Na +] by Ferrous Chloride (FeCl 2) and Oxidative Coupling and Chlorination of Silole Dianion [SiC 4Ph 4] 2-•2[Li +] by Cupric Chloride (CuCl 2). Molecules 2019; 24:molecules24203772. [PMID: 31635098 PMCID: PMC6832144 DOI: 10.3390/molecules24203772] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/09/2019] [Accepted: 10/15/2019] [Indexed: 11/19/2022] Open
Abstract
A reaction of silole anion {[MeSiC4Ph4]−•[Li+ or Na+] (1) with anhydrous ferrous chloride (FeCl2) in THF (tetrahydrofuran) gives 1,1′-bis(1-methyl-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) [Ph4C4Si(Me)-(Me)SiC4Ph4] (2) with precipitation of iron metal in high yield. Silole dianion {[SiC4Ph4]2−•2[Li+] (3) is added to anhydrous cupric chloride (CuCl2) in THF at −78 °C, then the dark red solution changes into a greenish solution. From the solution, a green solid is isolated, and stirring it in toluene at room temperature provides quantitatively 1,1′-bis(1-chloro-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) [Ph4C4Si(Cl)-(Cl)SiC4Ph4] (4) with precipitation of copper metal in toluene. The green solid is suggested to be 1,1′-bissilolyl bisradical [Ph4C4Si-SiC4Ph4]2• (8), and lithium cuprous chloride salts {[Li2CuICl2]+•[CuICl2]−}. Both reactions are initiated by single-electron transfer (SET) from the electron-rich anionic silole substrates (1 and 3) to iron(II) and copper(II).
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Affiliation(s)
- Jang-Hwan Hong
- Department of Nanopolymer Material Engineering, Pai Chai University, 155-40 Baejae-ro (Doma-Dong), Seo-Gu, Daejon 302-735, Korea.
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Dong Z, Schmidtmann M, Müller T. Potassium Salts of 2,5-Bis(trimethylsilyl)-Germolide: Switching between Aromatic and Non-Aromatic States. Chemistry 2019; 25:10858-10865. [PMID: 31173405 DOI: 10.1002/chem.201902238] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 06/06/2019] [Indexed: 11/06/2022]
Abstract
The reduction of a 1-mesityl-2,5-bis-trimethylsilylchlorogermole 8 with KC8 is reported. While the reaction with one equivalent of KC8 gave the dimer with a Ge-Ge bond 10, excess of KC8 (four equivalents) resulted in the formation of the potassium salt of the germole dianion, 11 with reductive cleavage of the Ge-C bond. Careful reduction with two equivalents of KC8 in THF provided the potassium salt of the planar germolide 5. Its solid-state structure revealed contact ion pairs with the potassium ion η5 -coordinated to the germacyclopentadienide ring. The molecular structure of the anion indicates a high degree of cyclic electron delocalization, in agreement with results from DFT calculations. Separation of the ion pair by complexation of the potassium ions with 18-crown-6 triggers the isomerization to germolide 6, which is characterized by a pyramidal coordination sphere of the germanium atom and a localized diene structure. The isomers 5 and 6 represent a rare example for a structurally manifested switch between a non-aromatic and an aromatic state induced by an external stimulus, in this case the complexation of the counter cation.
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Affiliation(s)
- Zhaowen Dong
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Str. 9-11, 26129, Oldenburg, Germany, European Union
| | - Marc Schmidtmann
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Str. 9-11, 26129, Oldenburg, Germany, European Union
| | - Thomas Müller
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Str. 9-11, 26129, Oldenburg, Germany, European Union
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Saito M. Creation of Exotic π-Electron Systems by Introduction of Heavy Elements and Expansion of the Concept of Aromaticity. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2018. [DOI: 10.1246/bcsj.20180047] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Masaichi Saito
- Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan
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10
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Han Z, Xie K, Ma X, Lu X. Synthesis and Characterization of a 2, 5-Bis(trimethylsilyl)-substituted Bis(1, 1′-silolide) Dianion. PHOSPHORUS SULFUR 2018. [DOI: 10.1080/10426507.2018.1452231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Zhengang Han
- Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, P. R. China
| | - Kefeng Xie
- Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, P. R. China
| | - Xiaofang Ma
- Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, P. R. China
| | - Xiaoquan Lu
- Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou, P. R. China
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