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Basu D, Ghosh B, Srivastava D, Patra N, Nayek HP. Mononuclear organogermanium(IV) catalysts for a [3 + 2] cycloaddition reaction. Dalton Trans 2024; 53:5648-5657. [PMID: 38441230 DOI: 10.1039/d4dt00239c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Three mononuclear Ge(IV) compounds, [(C6H5)2Ge(C13H8N2O4)] (1), [(C6H5)2Ge(C14H10N2O5)] (2), and [(C6H5)2Ge(C14H11NO3)] (3), have been synthesized by the reaction of pro-ligands H2L1 (C13H10N2O4), H2L2 (C14H12N2O5), and H2L3 (C14H13NO3) with (C6H5)2GeCl2 in the presence of triethylamine. All compounds were characterized by FT-IR spectroscopy and NMR spectroscopy. Single crystal X-ray diffraction analysis shows that the germanium(IV) atom exhibits a five-coordinated geometry in compounds 1 and 2. All compounds were screened as Lewis acid catalysts in the [3 + 2] cycloaddition reaction between sodium azide and various nitriles. The reactions resulted in the formation of 5-substituted 1H-tetrazoles with yields of up to 96%. Based on the experimental findings and DFT calculations, a plausible mechanism is proposed for the [3 + 2] cycloaddition reaction.
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Affiliation(s)
- Debayan Basu
- Department of Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India.
| | - Barshali Ghosh
- Department of Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India.
| | - Diship Srivastava
- Department of Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India.
| | - Niladri Patra
- Department of Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India.
| | - Hari Pada Nayek
- Department of Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, Jharkhand, India.
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2
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Moon HW, Wang F, Bhattacharyya K, Planas O, Leutzsch M, Nöthling N, Auer AA, Cornella J. Mechanistic Studies on the Bismuth-Catalyzed Transfer Hydrogenation of Azoarenes. Angew Chem Int Ed Engl 2023; 62:e202313578. [PMID: 37769154 DOI: 10.1002/anie.202313578] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 09/28/2023] [Accepted: 09/28/2023] [Indexed: 09/30/2023]
Abstract
Organobismuth-catalyzed transfer hydrogenation has recently been disclosed as an example of low-valent Bi redox catalysis. However, its mechanistic details have remained speculative. Herein, we report experimental and computational studies that provide mechanistic insights into a Bi-catalyzed transfer hydrogenation of azoarenes using p-trifluoromethylphenol (4) and pinacolborane (5) as hydrogen sources. A kinetic analysis elucidated the rate orders in all components in the catalytic reaction and determined that 1 a (2,6-bis[N-(tert-butyl)iminomethyl]phenylbismuth) is the resting state. In the transfer hydrogenation of azobenzene using 1 a and 4, an equilibrium between 1 a and 1 a ⋅ [OAr]2 (Ar=p-CF3 -C6 H4 ) is observed, and its thermodynamic parameters are established through variable-temperature NMR studies. Additionally, pKa -gated reactivity is observed, validating the proton-coupled nature of the transformation. The ensuing 1 a ⋅ [OAr]2 is crystallographically characterized, and shown to be rapidly reduced to 1 a in the presence of 5. DFT calculations indicate a rate-limiting transition state in which the initial N-H bond is formed via concerted proton transfer upon nucleophilic addition of 1 a to a hydrogen-bonded adduct of azobenzene and 4. These studies guided the discovery of a second-generation Bi catalyst, the rate-limiting transition state of which is lower in energy, leading to catalytic transfer hydrogenation at lower catalyst loadings and at cryogenic temperature.
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Affiliation(s)
- Hye Won Moon
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Feng Wang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Kalishankar Bhattacharyya
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Oriol Planas
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Markus Leutzsch
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Nils Nöthling
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Alexander A Auer
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Josep Cornella
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
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Lohmeyer L, Werr M, Kaifer E, Himmel H. Interplay and Competition Between Two Different Types of Redox-Active Ligands in Cobalt Complexes: How to Allocate the Electrons? Chemistry 2022; 28:e202201789. [PMID: 35894809 PMCID: PMC9804828 DOI: 10.1002/chem.202201789] [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: 06/10/2022] [Indexed: 01/09/2023]
Abstract
The field of molecular transition metal complexes with redox-active ligands is dominated by compounds with one or two units of the same redox-active ligand; complexes in which different redox-active ligands are bound to the same metal are uncommon. This work reports the first molecular coordination compounds in which redox-active bisguanidine or urea azine (biguanidine) ligands as well as oxolene ligands are bound to the same cobalt atom. The combination of two different redox-active ligands leads to mono- as well as unprecedented dinuclear cobalt complexes, being multiple (four or six) center redox systems with intriguing electronic structures, all exhibiting radical ligands. By changing the redox potential of the ligands through derivatisation, the electronic structure of the complexes could be altered in a rational way.
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Affiliation(s)
- Lukas Lohmeyer
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Marco Werr
- 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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Ansmann N, Hartmann D, Sailer S, Erdmann P, Maskey R, Schorpp M, Greb L. Synthesis and Characterization of Hypercoordinated Silicon Anions: Catching Intermediates of Lewis Base Catalysis. Angew Chem Int Ed Engl 2022; 61:e202203947. [PMID: 35438836 PMCID: PMC9325378 DOI: 10.1002/anie.202203947] [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: 03/16/2022] [Indexed: 11/24/2022]
Abstract
Anionic hypercoordinated silicates with weak donors were proposed as key intermediates in numerous silicon‐based reactions. However, their short‐lived nature rendered even spectroscopic observations highly challenging. Here, we characterize hypercoordinated silicon anions, including the first bromido‐, iodido‐, formato‐, acetato‐, triflato‐ and sulfato‐silicates. This is enabled by a new, donor‐free polymeric form of Lewis superacidic bis(perchlorocatecholato)silane 1. Spectroscopic, structural, and computational insights allow a reassessment of Gutmann's empirical rules for the role of silicon hypercoordination in synthesis and catalysis. The electronic perturbations of 1 exerted on the bound anions indicate pronounced substrate activation.
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Affiliation(s)
- Nils Ansmann
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Deborah Hartmann
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Sonja Sailer
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Philipp Erdmann
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Rezisha Maskey
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Marcel Schorpp
- Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Lutz Greb
- Department of Chemistry and Biochemistry-Inorganic Chemistry, Freie Universität Berlin, Fabeckstr. 34/36, 14195, Berlin, Germany
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5
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Ansmann N, Hartmann D, Sailer S, Erdmann P, Maskey R, Schorpp M, Greb L. Synthesis and Characterization of Hypercoordinated Silicon Anions: Catching Intermediates of Lewis Base Catalysis. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202203947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Nils Ansmann
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Deborah Hartmann
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Sonja Sailer
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Philipp Erdmann
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Rezisha Maskey
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Marcel Schorpp
- Anorganisch-Chemisches Institut Ruprecht-Karls-Universität Heidelberg Im Neuenheimer Feld 270 69120 Heidelberg Germany
| | - Lutz Greb
- Department of Chemistry and Biochemistry-Inorganic Chemistry Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
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First Evidence of Tris(catecholato)silicate Formation from Hydrolysis of an Alkyl Bis(catecholato)silicate. Molecules 2022; 27:molecules27082521. [PMID: 35458719 PMCID: PMC9032887 DOI: 10.3390/molecules27082521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/08/2022] [Accepted: 04/11/2022] [Indexed: 02/05/2023] Open
Abstract
The hydrolysis of 3-ammoniumpropylbis(catecholato)silicate 1, giving two different silica-based materials containing different amounts of tris(catecholato)silicate, is reported. The latter species can be formed through an attack of catechol to the silicon atom in the pentacoordinate complex, in which the silicon-carbon bond is further activated toward electrophilic proton cleavage. The Knoevenagel reaction was used as a probe in order to test the availability of functional groups on the surface of such materials.
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Basu D, Nayek HP. Bis(catecholato)germane: An Effective Catalyst for Friedel-Crafts Alkylation Reaction. Dalton Trans 2022; 51:10587-10594. [DOI: 10.1039/d2dt01721k] [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
Bis(catecholato)germane, [Ge(C6H4O2)2(H2O)2] (1) was synthesized by the reaction of catechol and germanium oxide in water according to a reported method. Complex 1 was characterized by FT-IR spectroscopy, NMR spectroscopy and...
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8
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Hypercoordinate germanium complexes with phenanthrene-9,10-diolate ligands: synthesis, structure, and electronic properties. MENDELEEV COMMUNICATIONS 2022. [DOI: 10.1016/j.mencom.2022.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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Walter P, Hübner O, Kaifer E, Himmel HJ. Proton-Coupled Electron Transfer (PCET) with 1,4-Bisguanidino-Benzene Derivatives: Comparative Study and Use in Acid-Initiated C-H Activation. Chemistry 2021; 27:11943-11956. [PMID: 34132428 PMCID: PMC8457230 DOI: 10.1002/chem.202101539] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Indexed: 11/18/2022]
Abstract
Proton‐coupled electron transfer (PCET) is of key importance in modern synthetic chemistry. Redox‐active guanidines were established by our group as valuable alternatives to toxic high‐potential benzoquinones in a variety of different PCET reactions. In this work, the PCET reactivity of a series of 1,4‐bisguanidino‐benzenes varying in their redox potentials and proton affinities is evaluated. The relevant redox and protonation states are fully characterized, and the compounds sorted with respect to their PCET reactivity by comparative PCET experiments supplemented by quantum‐chemical calculations. Depending on the studied reactions, the driving force is either electron transfer or proton transfer; thereby the influence of both processes on the overall reactivity could be assessed. Then, two of the PCET reagents are applied in representative oxidative aryl‐aryl coupling reactions, namely the intramolecular coupling of 3,3’’‐4,4’’‐tetramethoxy‐o‐terphenyl to give the corresponding triphenylene, the intermolecular coupling of N‐ethylcarbazole to give N,N’‐diethyl‐3,3’‐bicarbazole, and in the oxidative lactonization of 2‐[(4‐methoxyphenyl)methyl]‐benzoic acid. Under mild conditions, the reactions proceed fast and efficient. Only small amounts of acid are needed, in clear contrast to the corresponding coupling reactions with traditional high‐potential benzoquinones such as DDQ or chloranil requiring a large excess of a strong acid.
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Affiliation(s)
- Petra Walter
- Inorganic Chemistry, Ruprecht-Karls University of Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Olaf Hübner
- 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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Maskey R, Bendel C, Malzacher J, Greb L. Completing the Redox-Series of Silicon Trisdioxolene: ortho-Quinone and Lewis Superacid Make a Powerful Redox Catalyst. Chemistry 2020; 26:17386-17389. [PMID: 33108014 PMCID: PMC7839739 DOI: 10.1002/chem.202004712] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Indexed: 12/25/2022]
Abstract
Quinones are mild oxidants, the redox potentials of which can be increased by supramolecular interactions. Whereas this goal has been achieved by hydrogen bonding or molecular encapsulation, a Lewis acid-binding strategy for redox amplification of quinones is unexplored. Herein, the redox chemistry of silicon tris(perchloro)dioxolene 1 was studied, which is the formal adduct of ortho-perchloroquinone QCl with the Lewis superacid bis(perchlorocatecholato)silane 2. By isolating the anionic monoradical 1.- , the redox-series of a century-old class of compounds was completed. Cyclic voltammetry measurements revealed that the redox potential in 1 was shifted by more than 1 V into the anodic direction compared to QCl , reaching that of "magic blue" or NO+ . It allowed oxidation of challenging substrates such as aromatic hydrocarbons and could be applied as an efficient redox catalyst. Remarkably, this powerful reagent formed in situ by combining the two commercially available precursors SiI4 and QCl .
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Affiliation(s)
- Rezisha Maskey
- Institute of Inorganic Chemistry, Ruprecht Karl University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Christoph Bendel
- Institute of Inorganic Chemistry, Ruprecht Karl University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Jonas Malzacher
- Institute of Inorganic Chemistry, Ruprecht Karl University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Lutz Greb
- Institute of Inorganic Chemistry, Ruprecht Karl University Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
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