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Walther L, Radacki K, Dewhurst RD, Bertermann R, Finze M, Braunschweig H. All-Inorganic sp-Chain Ligands: Isoelectronic B/N Analogues of E. O. Fischer's Alkynylcarbynes. Angew Chem Int Ed Engl 2024; 63:e202404930. [PMID: 38746995 DOI: 10.1002/anie.202404930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Indexed: 07/16/2024]
Abstract
Borylation of a tungsten-bound N2 ligand and halide abstraction provides access to a cationic complex with an unprecedented linear NNBR ligand. This complex undergoes [3+2] cycloaddition with azides, and an unexpected chain-extension reaction with an iminoborane, leading to a complex with a five-atom B/N chain. These two [NNBR]-containing complexes, inorganic analogues of E. O. Fischer's alkynylcarbynes, are very rare examples of molecules containing all-inorganic chains of sp-hybridized atoms.
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Affiliation(s)
- Luis Walther
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Krzysztof Radacki
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Rian D Dewhurst
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Rüdiger Bertermann
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Maik Finze
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Holger Braunschweig
- Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
- Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
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Gupta D, Einholz R, Bettinger HF. Strain induced reactivity of cyclic iminoboranes: the (2 + 2) cycloaddition of a 1 H-1,3,2-diazaborepine with ethene. Chem Sci 2024; 15:666-674. [PMID: 38179531 PMCID: PMC10763563 DOI: 10.1039/d3sc04901a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Accepted: 11/19/2023] [Indexed: 01/06/2024] Open
Abstract
Iminoboranes have gathered immense attention due to their reactivity and potential applications as isoelectronic and isosteric alkynes. While cyclic alkynes are well investigated and useful reagents, cyclic iminoboranes are underexplored and their existence was inferred only via trapping experiments. We report the first direct spectroscopic evidence of a cyclic seven-membered iminoborane, 1-(tert-butyldimethylsilyl)-1H-1,3,2-diazaborepine 2, under cryogenic matrix isolation conditions. The amino-iminoborane 2 was photochemically generated in solid argon at 4 K from 2-azido-1-(tert-butyldimethylsilyl)-1,2-dihydro-1,2-azaborinine (3) and was characterized using FT-IR, UV-vis spectroscopy, and computational chemistry. The characteristic BN stretching vibration (1751 cm-1) is shifted by about 240 cm-1 compared to linear amino-iminoboranes indicating a significant weakening of the bond. The Lewis acidity value determined computationally (LAB = 9.1 ± 2.6) is similar to that of boron trichloride, and twelve orders of magnitude lower than that of 1,2-azaborinine (BN-aryne, LAB = 21.5 ± 2.6), a six-membered cyclic iminoborane. In contrast to the latter, the reduced ring strain of 2 precludes nitrogen fixation, but it unexpectedly allows facile (2 + 2) cycloaddition reaction with C2H4 under matrix isolation conditions at 30 K.
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Affiliation(s)
- Divanshu Gupta
- Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Ralf Einholz
- Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
| | - Holger F Bettinger
- Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany
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3
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Kimura Y, Lugo-Fuentes LI, Saito S, Jimenez-Halla JOC, Barroso-Flores J, Yamamoto Y, Nakamoto M, Shang R. A boron, nitrogen-containing heterocyclic carbene (BNC) as a redox active ligand: synthesis and characterization of a lithium BNC-aurate complex. Dalton Trans 2022; 51:7899-7906. [PMID: 35535973 DOI: 10.1039/d2dt01083f] [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
Stabilization of low oxidation gold anions as aurate or auride by organic ligands has long been a synthetic challenge, owing to the proneness of low-valent gold centres to cluster. Despite being the most electronegative metal, isolable gold(I) aurate complexes have only been obtained from a few σ-withdrawing organo- and organo-main group ligands. Stabilization of highly-reduced gold complexes by π-modulating redox active ligands has only been achieved by cyclic (amino)(alkyl)carbene (CAAC), which is limited to 1e--reduction to form neutral gold(0) complexes. This work reports a simple modular synthesis of a boron, nitrogen-containing heterocyclic carbene (ClBNC) at a gold(I) center through metal-assisted coupling between azadiboriridine and isocyanides. The anionic electrophilic ClBNC ligand in the gold(I) complex [(ClBNC)AuPMe3] (3a and 3b) allows a 2e--reduction to form the first η1-carbene aurate complex [(BNC)AuPMe3]Li(DME) (5a, DME = dimethoxyethane). Single crystal crystallographic analysis and computational studies of these complexes revealed a highly π-withdrawing character of the neutral 4π B,N-heterocyclic carbene (BNC) moiety and a 6π weakly aromatic character with π-donating properties to the gold(I) fragment in its reduced form, showcasing the first cyclic carbene ligand that allows electronic tunability between π-withdrawing (Fischer-type)- and π-donating (Schrock-type) properties.
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Affiliation(s)
- Yoshitaka Kimura
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
| | - Leonardo I Lugo-Fuentes
- Department of Chemistry, Division of Natural and Exact Sciences, University of Guanajuato, Campus Gto, Noria Alta s/n 36050, Guanajuato, Mexico
| | - Souta Saito
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
| | - J Oscar C Jimenez-Halla
- Department of Chemistry, Division of Natural and Exact Sciences, University of Guanajuato, Campus Gto, Noria Alta s/n 36050, Guanajuato, Mexico
| | - Joaquín Barroso-Flores
- Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM México and Instituto de Química, Universidad Nacional Autónoma de México, Carretera Toluca-Atlacomulco Km. 14.5, Unidad San Cayetano, 50200 Toluca de Lerdo, Ciudad de Méico 04510, Mexico
| | - Yohsuke Yamamoto
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
| | - Masaaki Nakamoto
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
| | - Rong Shang
- Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
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Major CJ, Qu ZW, Grimme S, Stephan DW. The Non-Ancillary Nature of Trimethylsilylamide Substituents in Boranes and Borinium Cations. Chemistry 2022; 28:e202200698. [PMID: 35262980 PMCID: PMC9324859 DOI: 10.1002/chem.202200698] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Indexed: 11/21/2022]
Abstract
The known boranes (R(Me3Si)N)2BF (R=Me3Si 1, tBu 2, C6F53, o‐tol 4, Mes 5, Dipp 6) and borinium salts (R(Me3Si)N)2B][B(C6F5)4] (R=Me3Si 7, tBu 8) are prepared and fully characterized. Compound 7 is shown to react with phosphines to generate [R3PSiMe3]+ and [R3PH]+ (R=Me, tBu). Efforts to generate related borinium cations via fluoride abstraction from (R(Me3Si)N)2BF (R=C6F53, o‐tol 4, Mes 5) gave complex mixtures suggesting multiple reaction pathways. However for R=Dipp 6, the species [(μ‐F)(SiMe2N(Dipp))2BMe][B(C6F5)4] was isolated as the major product, indicating methyl abstraction from silicon and F/Me exchange on boron. These observations together with state‐of‐the‐art DFT mechanistic studies reveal that the trimethylsilyl‐substituents do not behave as ancillary subsitutents but rather act as sources of proton, SiMe3 and methyl groups.
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Affiliation(s)
- Christopher J Major
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada
| | - Zheng-Wang Qu
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Douglas W Stephan
- Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S3H6, Canada
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