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Filbeck E, Cremer S, Jansen MCF, Kaifer E, Himmel HJ. Halide-Coupled Double Electron Transfer with Electron-Rich Diboranes. Chemistry 2023; 29:e202302911. [PMID: 37728170 DOI: 10.1002/chem.202302911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 09/19/2023] [Accepted: 09/20/2023] [Indexed: 09/21/2023]
Abstract
The ditriflato-diborane B2 (μ-hpp)2 (OTf)2 (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) acts as a stable surrogate of the elusive dication [B2 (hpp)2 ]2+ , being both electrophilic (vacant boron p orbitals) and nucleophilic (filled B-B bond orbital). This combination of seemingly contrasting behaviors could be used to develop a metallomimetic diborane chemistry, with Lewis σ-basic and π-acidic substrates being bound and reduced at the diborane. Here, we report on a novel reaction type within this general theme, in which double electron transfer from the diboron unit to the boron-bound organic substrate is coupled with halide transfer in the other direction. Novel diborylated dienamines are synthesized in this way. The scope of this unprecedented reaction motif and the reaction pathways are elucidated.
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Affiliation(s)
- Erik Filbeck
- Inorganic Chemistry, Ruprecht-Karls University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Sebastian Cremer
- Inorganic Chemistry, Ruprecht-Karls University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Moritz C F Jansen
- Inorganic Chemistry, Ruprecht-Karls University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Elisabeth Kaifer
- Inorganic Chemistry, Ruprecht-Karls University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hans-Jörg Himmel
- Inorganic Chemistry, Ruprecht-Karls University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
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2
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Kistner L, Kowatsch D, Marz A, Kaifer E, Himmel H. Directed Synthesis and Chemistry of Unsymmetric Dicationic Diboranes and Their Use in Frustrated Lewis Pair-like Chemistry. Chemistry 2022; 28:e202104016. [PMID: 35061309 PMCID: PMC9305129 DOI: 10.1002/chem.202104016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Indexed: 11/15/2022]
Abstract
The chemistry of dicationic diboranes with two BII atoms that are engaged in direct B-B bonding is by enlarge unexplored, although these molecules have intriguing properties due to their combined Lewis acidic and electron-donor properties. Unsymmetric dicationic diboranes are extremely rare, but especially attractive due to their polarized B-B bond. In this work we report the directed synthesis of several stable unsymmetric dicationic diboranes by reaction between the electron-rich ditriflato-diborane B2 (hpp)2 (OTf)2 (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-α]pyrimidinate) and phosphino-pyridines, establishing B-N and B-P bonds with the diborane concomitant with triflate elimination. In the case of 2-((ditertbutylphosphino)methyl)pyridine, the B-N bond is formed instantly, but the B-P bond formation requires (due to steric constraints) several days at ambient conditions for completion, creating an intermediate that could be used for frustrated Lewis pair (FLP)-like chemistry. Here we test its reaction with an aldehyde, and propose a new type of FLP-like chemistry.
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Affiliation(s)
- Lucas Kistner
- Anorganisch-Chemisches InstitutRuprecht-Karls Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Dario Kowatsch
- Anorganisch-Chemisches InstitutRuprecht-Karls Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Andreas Marz
- Anorganisch-Chemisches InstitutRuprecht-Karls Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches InstitutRuprecht-Karls Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches InstitutRuprecht-Karls Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
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3
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Filbeck E, Widera A, Kaifer E, Himmel H. Polycationic Redox-Active Cyclophanes with Integrated Electron-Rich Diboron Units. Chemistry 2021; 27:15737-15750. [PMID: 34459521 PMCID: PMC9291520 DOI: 10.1002/chem.202102656] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Indexed: 11/29/2022]
Abstract
Cationic cyclophanes are widely used in a variety of applications in supramolecular chemistry and materials science. In this work the authors systematically study the integration of electron-rich diboron units with BII atoms into polycationic cyclophanes with viologen-like electron-acceptor units. They also report a first hexacationic cage-compound in which three diboron units connect two tris(4-pyridyl)triazine acceptor units. Moreover, di- and tetracationic open-structure compounds, in which one diboron unit connects two bispyridyl groups, were synthesized and the properties compared to those of the corresponding closed structures (cyclophanes). The combination of diboron electron-donor units and bi- or oligopyridyl electron-acceptor units leads to intriguing optical and redox properties.
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Affiliation(s)
- Erik Filbeck
- Institute of Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Anna Widera
- Institute of Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Elisabeth Kaifer
- Institute of Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Institute of Inorganic ChemistryRuprecht-Karls University of HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
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4
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Affiliation(s)
- Anna Widera
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Erik Filbeck
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hans‐Jörg Himmel
- Anorganisch‐Chemisches Institut Ruprecht‐Karls‐Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
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5
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Schön F, Greb L, Kaifer E, Himmel H. Desymmetrization of Dicationic Diboranes by Isomerization Catalyzed by a Nucleophile. Angew Chem Int Ed Engl 2020; 59:9127-9133. [PMID: 32181953 PMCID: PMC7317786 DOI: 10.1002/anie.202001640] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/16/2020] [Indexed: 11/11/2022]
Abstract
Cationic monoboranes exhibit a rich chemistry. By constrast, only a few cationic diboranes are known, that all are symmetrically substituted. In this work, the first unsymmetrically substituted dicationic diboranes, featuring sp2 -sp2 -hybridized boron atoms, are reported. The compounds are formed by intramolecular rearrangement from preceding isomeric symmetrically substituted dicationic diboranes, a process that is catalyzed by nucleophiles. From the temperature-dependence of the isomerization rate, activation parameters for this unprecedented rearrangement are derived. The difference in fluoride ion affinity between the two boron atoms and the bonding situation in these unique unsymmetrical dicationic diboranes are evaluated.
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Affiliation(s)
- Florian Schön
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Lutz Greb
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
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6
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Schön F, Greb L, Kaifer E, Himmel H. Desymmetrization of Dicationic Diboranes by Isomerization Catalyzed by a Nucleophile. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202001640] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Florian Schön
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Lutz Greb
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
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7
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Widera A, Filbeck E, Wadepohl H, Kaifer E, Himmel H. Electron-Rich, Lewis Acidic Diborane Meets N-Heterocyclic Aromatics: Formation and Electron Transfer in Cyclophane Boranes. Chemistry 2020; 26:3435-3440. [PMID: 31943435 PMCID: PMC7155121 DOI: 10.1002/chem.202000189] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Indexed: 01/17/2023]
Abstract
Herein reported are the reactions of an electron-rich, Lewis acidic diborane with N-heterocyclic aromatics to give first members of an unprecedented family of highly charged cationic cyclophanes with diboranyl units. Tetracationic cyclophanes with 4,4'-bipyridine/ 1,2-bis(4-pyridyl)ethylene and diboranyl units were synthesized and their redox chemistry was studied. Cyclisation of two diboranyl and two pyrazine units is accompanied by electron transfer from the diboranyl unit to the pyrazine. Our results pave the way for the integration of redox-active diboranyl units into cyclophanes and supramolecular structures.
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Affiliation(s)
- Anna Widera
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069121HeidelbergGermany
| | - Erik Filbeck
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069121HeidelbergGermany
| | - Hubert Wadepohl
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069121HeidelbergGermany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069121HeidelbergGermany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069121HeidelbergGermany
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8
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Englert L, Stoy A, Arrowsmith M, Muessig JH, Thaler M, Deißenberger A, Häfner A, Böhnke J, Hupp F, Seufert J, Mies J, Damme A, Dellermann T, Hammond K, Kupfer T, Radacki K, Thiess T, Braunschweig H. Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity. Chemistry 2019; 25:8612-8622. [DOI: 10.1002/chem.201901437] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Indexed: 02/02/2023]
Affiliation(s)
- Lukas Englert
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Andreas Stoy
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Merle Arrowsmith
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Jonas H. Muessig
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Melanie Thaler
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Andrea Deißenberger
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Alena Häfner
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Julian Böhnke
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Florian Hupp
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Jens Seufert
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Jan Mies
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Alexander Damme
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Theresa Dellermann
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Kai Hammond
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Thomas Kupfer
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Krzysztof Radacki
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Torsten Thiess
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Holger Braunschweig
- Institute for Inorganic Chemistry and theInstitute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
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9
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Himmel H. Electron‐Deficient Triborane and Tetraborane Ring Compounds: Synthesis, Structure, and Bonding. Angew Chem Int Ed Engl 2019; 58:11600-11617. [DOI: 10.1002/anie.201900563] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Hans‐Jörg Himmel
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
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10
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Himmel H. Elektronen‐defizitäre Triboran‐ und Tetraboran‐Ringverbindungen: Synthese, Struktur und Bindung. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201900563] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Hans‐Jörg Himmel
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Deutschland
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11
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Elias J, Kaifer E, Himmel HJ. Boron-Boron Dehydrocoupling of Boranes Initiated by Reaction with Iodine. Chemistry 2019; 25:6553-6561. [PMID: 30821401 DOI: 10.1002/chem.201900671] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Indexed: 01/07/2023]
Abstract
A new boron-boron dehydrocoupling strategy was established, providing convenient access to some diborane(4) compounds starting from simple borane adducts under mild conditions. In contrast to the traditional pathway using a reducing reagent, the reduction from BIII to BII was paradoxically initiated by the addition of the oxidation-reagent iodine. A reaction pathway for this unusual reaction was proposed based on quantum-chemical calculations.
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Affiliation(s)
- Jana Elias
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hans-Jörg Himmel
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
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12
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Widera A, Wadepohl H, Himmel H. Vier Boratome, vier positive Ladungen und vier Gerüstelektronen: ein fluoreszierendes σ‐aromatisches Tetraboran(4). Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201814041] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Anna Widera
- Institut für Anorganische ChemieRuprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Deutschland
| | - Hubert Wadepohl
- Institut für Anorganische ChemieRuprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Deutschland
| | - Hans‐Jörg Himmel
- Institut für Anorganische ChemieRuprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Deutschland
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13
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Widera A, Wadepohl H, Himmel HJ. Four Boron Atoms, Four Positive Charges, and Four Skeletal Electrons: A Fluorescent σ-Aromatic Tetraborane(4). Angew Chem Int Ed Engl 2019; 58:5897-5901. [PMID: 30637912 DOI: 10.1002/anie.201814041] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Indexed: 11/10/2022]
Abstract
Reaction of a ditriflatodiborane compound with the Lewis acids AlCl3 or GaCl3 leads to abstraction of the two triflate substituents and dimerization of the resulting dicationic diborane to give a σ-aromatic tetracationic tetraborane with a planar, rhomboid B4 core. The compound exhibits four skeletal σ-electrons involved in two (3c,2e) bonds and represents the first stable fourfold base-stabilized [B4 H4 ]4+ analogue. The product is isolated from the reaction mixture in the form of bright orange crystals that display fluorescence. Further analysis shows that the new tetraborane(4) is stabilized in the solid state by the lattice energy. It exhibits an extremely high electron affinity and is only stable in solution after one-electron reduction to the radical cation.
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Affiliation(s)
- Anna Widera
- Institute of Inorganic Chemistry, Ruprecht-Karls University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hubert Wadepohl
- Institute of Inorganic Chemistry, Ruprecht-Karls University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hans-Jörg Himmel
- Institute of Inorganic Chemistry, Ruprecht-Karls University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
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14
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Zhao LY, Chen JY, Li WC, Lu AH. B2O3: A heterogeneous metal-free Lewis acid catalyst for carbon dioxide fixation into cyclic carbonates. J CO2 UTIL 2019. [DOI: 10.1016/j.jcou.2018.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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15
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Franz D, Inoue S. Cationic Complexes of Boron and Aluminum: An Early 21st Century Viewpoint. Chemistry 2018; 25:2898-2926. [PMID: 30113744 DOI: 10.1002/chem.201803370] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Indexed: 01/03/2023]
Abstract
Boron and aluminum are lighter Group 13 elements, found in daily life commodities, and considered environmentally benign. Nevertheless, they markedly differ in their elemental properties (e.g., metal character, atomic radius). The use of Lewis acidic complexes of boron and aluminum for methods of bond activation and catalysis (e.g., hydrogenation of unsaturated substrates, polymerization of olefins and epoxides) is quickly expanding. The introduction of cationic charge may boost the metalloid-centered Lewis acidity and allow for its fine-tuning particularly with regard to preference for "hard" or "soft" Lewis bases (i.e., substrates). Especially the isolation of low-coordinate cations (number of ligand atoms smaller than four) demands elaborate techniques of thermodynamic and kinetic stabilization (i.e., electronic saturation and steric shielding) by a ligand system. Furthermore, the properties of the solvent and the counteranion must be considered with care. Here, selected examples of boron and aluminum cations are described.
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Affiliation(s)
- Daniel Franz
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstr. 4, 85748, Garching bei München, Germany
| | - Shigeyoshi Inoue
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstr. 4, 85748, Garching bei München, Germany
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