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Kraft F, Koszinowski K. Intramolecular Phenyl Transfer from a Boronate to Lithium in the Gas Phase Reveals Crucial Role of Solvation in Transmetalations. Chemistry 2024:e202303653. [PMID: 38427965 DOI: 10.1002/chem.202303653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 03/01/2024] [Accepted: 03/01/2024] [Indexed: 03/03/2024]
Abstract
In contrast to its behavior in solution, the adduct [(LiBr)(tBu)(Ph)Bpin]- (pin=pinacol) transfers its phenyl anion from boron to lithium upon fragmentation in the gas phase. Quantum chemical calculations predict this exceptional transmetalation to be exothermic relative to the separated reactants, [(tBu)(Ph)Bpin]- and LiBr, which we attribute to the high phenyl-anion affinity of the coordinatively unsaturated LiBr unit. The addition of a single molecule of tetrahydrofuran drastically reduces the phenyl-anion affinity of LiBr and thereby renders the transmetalation from boron to lithium endothermic. Thus, the probed system highlights the importance of solvation and ligation effects in transmetalations. For correctly predicting the direction, in which these reactions proceed, it is not sufficient to consider the electronegativities or partial charges of the involved metals or metalloids. Instead, the individual coordination states and their changes over the course of the reaction must be taken into account.
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Affiliation(s)
- Finn Kraft
- Institute of Organic and Biomolecular Chemistry, Georg-August Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular Chemistry, Georg-August Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
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2
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Eisele NF, Rahrt R, Giachanou L, Shikho F, Koszinowski K. Gas-Phase Alkali-Metal Cation Affinities of Stabilized Enolates. Chemistry 2023; 29:e202302540. [PMID: 37752885 DOI: 10.1002/chem.202302540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 09/23/2023] [Accepted: 09/25/2023] [Indexed: 09/28/2023]
Abstract
The chemistry of alkali-metal enolates is dominated by ion pairing. To improve our understanding of the intrinsic interactions between the alkali-metal cations and the enolate anions, we have applied Cooks' kinetic method to determine relative M+ (M=Li, Na, K) affinities of the stabilized enolates derived from acetylacetone, ethyl acetoacetate, diethyl malonate, ethyl cyanoacetate, 2-cyanoacetamide, and methyl malonate monoamide in the gas phase. Quantum chemical calculations support the experimental results and moreover afford insight into the structures of the alkali-metal enolate complexes. The affinities decrease with increasing size of the alkali-metal cations, reflecting weaker electrostatic interactions and lower charge densities of the free M+ ions. For the different enolates, a comparison of their coordinating abilities is complicated by the fact that some of the free anions undergo conformational changes resulting in stabilizing intramolecular interactions. If these complicating effects are disregarded, the M+ affinities correlate with the electron density of the chelating functionalities, that is, the carbonyl and/or the nitrile groups of the enolates. A comparison with the known association constants of the corresponding alkali-metal enolates in solution points to the importance of solvation effects for these systems.
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Affiliation(s)
- Niklas F Eisele
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Rene Rahrt
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Lamprini Giachanou
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Fadi Shikho
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
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3
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Zimmer B, Auth T, Koszinowski K. Unimolecular reactivity of [Cu(R)(CF3)3]- complexes (R = organyl): stepwise vs. concerted mechanism in copper-mediated trifluoromethylation. Chemistry 2023:e202300725. [PMID: 37139922 DOI: 10.1002/chem.202300725] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 04/28/2023] [Accepted: 05/02/2023] [Indexed: 05/05/2023]
Abstract
The cuprate complexes [Cu(R)(CF3)3]- (R = organyl) offer an efficient synthetic access to valuable trifluoromethylation products RCF3. Here, we use electrospray-ionization mass spectrometry to analyze the formation of these intermediates in solution and probe their fragmentation pathways in the gas phase. Furthermore, we explore the potential energy surfaces of these systems by quantum chemical calculations. Upon collisional activation, the [Cu(R)(CF3)3]- complexes (R = Me, Et, Bu, s Bu, allyl) afford the product ions [Cu(CF3)3]•- and [Cu(CF3)2]-. The former obviously results from an R• loss, whereas the latter originates either from the stepwise release of R• and CF3• radicals or a concerted reductive elimination of RCF3. The gas-phase fragmentation experiments as well as the quantum chemical calculations indicate that the preference for the stepwise reaction toward [Cu(CF3)2]- increases with the stability of the formed organyl radical R•. This finding suggests that the recombination of R• and CF3• radicals may possibly contribute to the formation of RCF3 from [Cu(R)(CF3)3]- in synthetic applications. In contrast, the [Cu(R)(CF3)3]- complexes (R = aryl) only yield [Cu(CF3)2]- when subjected to collision-induced dissociation. These species exclusively undergo a concerted reductive elimination because the competing stepwise pathway is disfavored by the low stability of aryl radicals.
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Affiliation(s)
- Bastian Zimmer
- University of Göttingen Faculty of Chemistry: Georg-August-Universitat Gottingen Fakultat fur Chemie, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Göttingen, GERMANY
| | - Thomas Auth
- Georg-August-Universitat Gottingen Fakultat fur Chemie, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Göttingen, GERMANY
| | - Konrad Koszinowski
- Georg-August-Universitat Gottingen, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Göttingen, GERMANY
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4
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Eisele NF, Peters M, Koszinowski K. Live Monitoring of Anionic Living Polymerizations by Electrospray-Ionization Mass Spectrometry. Chemistry 2023; 29:e202203762. [PMID: 36596722 DOI: 10.1002/chem.202203762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/30/2022] [Accepted: 01/03/2023] [Indexed: 01/05/2023]
Abstract
Anionic polymerizations are of exceptional practical importance, but difficult to analyze due to the high reactivity of the growing polymer chains. Here, we demonstrate that electrospray-ionization mass spectrometry (ESI-MS) permits direct observation of the active carbanionic intermediates formed in the anionic ring-opening polymerization of 1-cyanocyclopropanecarboxylate in tetrahydrofuran. This includes the identification of a side product, as well as real-time analysis of the polymerization reaction. From the mass spectra obtained, we can derive not only the mean molar mass and the polydispersity, but also the rate constants for the initiation and the individual propagation steps. The initiation proceeds significantly faster than the propagation steps. Accordingly, the examined reaction corresponds to a living polymerization, as we also confirmed by additional control experiments. Besides giving detailed insight into the reaction system probed here, we also expect the presented methodology to make possible the in-situ analysis of further anionic polymerizations.
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Affiliation(s)
- Niklas F Eisele
- Institute of Organic and Biomolecular Chemistry, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Matthias Peters
- Institute of Organic and Biomolecular Chemistry, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular Chemistry, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
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Eisele NF, Peters M, Koszinowski K. Live Monitoring of Anionic Living Polymerizations by Electrospray‐Ionization Mass Spectrometry. Chemistry 2023. [DOI: 10.1002/chem.202300363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Affiliation(s)
- Niklas F. Eisele
- Institute of Organic and Biomolecular Chemistry Universität Göttingen Tammannstraße 2 37077 Göttingen Germany
| | - Matthias Peters
- Institute of Organic and Biomolecular Chemistry Universität Göttingen Tammannstraße 2 37077 Göttingen Germany
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular Chemistry Universität Göttingen Tammannstraße 2 37077 Göttingen Germany
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Rahrt R, Koszinowski K. C versus O Protonation in Zincate Anions: A Simple Gas-Phase Model for the Surprising Kinetic Stability of Organometallics. Chemistry 2023; 29:e202203611. [PMID: 36692992 DOI: 10.1002/chem.202203611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 01/18/2023] [Accepted: 01/24/2023] [Indexed: 01/25/2023]
Abstract
For better understanding the intrinsic reactivity of organozinc reagents, we have examined the protolysis of the isolated zincate ions Et3 Zn- , Et2 Zn(OH)- , and Et2 Zn(OH)2 Li- by 2,2,2-trifluoroethanol in the gas phase. The protonation of the hydroxy groups and the release of water proceed much more efficiently than the protonation of the ethyl groups and the liberation of ethane. Quantum-chemical computations and statistical-rate theory calculations fully reproduce the experimental findings and attribute the lower reactivity of the more basic ethyl moiety to higher intrinsic barriers, which override the thermodynamic preference for its protonation. Thus, our minimalistic gas-phase model provides evidence for the intrinsically low reactivity of organozinc reagents toward proton donors and helps to explain their remarkable kinetic stability against moisture and even protic media.
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Affiliation(s)
- Rene Rahrt
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
- Wöhler Research Institute for Sustainable Chemistry, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
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Lülf S, Guo L, Parchomyk T, Harvey JN, Koszinowski K. Microscopic Reactivity of Phenylferrate Ions toward Organyl Halides. Chemistry 2022; 28:e202202030. [PMID: 35948515 PMCID: PMC9826238 DOI: 10.1002/chem.202202030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Indexed: 01/11/2023]
Abstract
Despite its practical importance, organoiron chemistry remains poorly understood due to its mechanistic complexity. Here, we focus on the oxidative addition of organyl halides to phenylferrate anions in the gas phase. By mass-selecting individual phenylferrate anions, we can determine the effect of the oxidation state, the ligation, and the nuclearity of the iron complex on its reactions with a series of organyl halides RX. We find that Ph2 Fe(I)- and other low-valent ferrates are more reactive than Ph3 Fe(II)- ; Ph4 Fe(III)- is inert. The coordination of a PPh3 ligand or the presence of a second iron center lower the reactivity. Besides direct cross-coupling reactions resulting in the formation of RPh, we also observe the abstraction of halogen atoms. This reaction channel shows the readiness of organoiron species to undergo radical-type processes. Complementary DFT calculations afford further insight and rationalize the high reactivity of the Ph2 Fe(I)- complex by the exothermicity of the oxidative addition and the low barriers associated with this reaction step. At the same time, they point to the importance of changes of the spin state in the reactions of Ph3 Fe(II)- .
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Affiliation(s)
- Stefan Lülf
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstr. 237077GöttingenGermany
| | - Luxuan Guo
- Department of ChemistryKU LeuvenCelestijnenlaan 200FB-3001LeuvenBelgium
| | - Tobias Parchomyk
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstr. 237077GöttingenGermany
| | - Jeremy N. Harvey
- Department of ChemistryKU LeuvenCelestijnenlaan 200FB-3001LeuvenBelgium
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstr. 237077GöttingenGermany,Wöhler Research Institute for Sustainable ChemistryUniversität GöttingenTammannstr. 237077GöttingenGermany
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8
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Kreyenschmidt F, Eisele NF, Hevelke V, Rahrt R, Kreyenschmidt A, Koszinowski K. In-Situ Analysis of Anionic Coordination Polymerizations by Electrospray-Ionization Mass Spectrometry. Angew Chem Int Ed Engl 2022; 61:e202210211. [PMID: 35977914 PMCID: PMC9828445 DOI: 10.1002/anie.202210211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Indexed: 01/12/2023]
Abstract
Anionic coordination polymerizations proceed via highly reactive intermediates, whose in situ analysis has remained difficult. Here, we show that electrospray-ionization mass spectrometry is a promising method to obtain detailed information on the polymerization process. Focusing on polymerization reactions of 1,3-dienes initiated by CoCl2 /RLi (R=Me, nBu, tBu, Ph), we directly observe the growing polymer chains and characterize the active anionic cobalt centers by gas-phase fragmentation experiments. On the basis of these results, we suggest a plausible mechanism for the polymerization reaction. Moreover, the ESI mass spectra permit the determination of molecular weight distributions, which are in good agreement with those derived from NMR-spectroscopic as well as MALDI mass-spectrometric measurements, and afford a wealth of kinetic data.
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Affiliation(s)
- Friedrich Kreyenschmidt
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstraße 237077GöttingenGermany
| | - Niklas F. Eisele
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstraße 237077GöttingenGermany
| | - Valentin Hevelke
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstraße 237077GöttingenGermany
| | - Rene Rahrt
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstraße 237077GöttingenGermany
| | | | - Konrad Koszinowski
- Institut für Organische und Biomolekulare ChemieUniversität GöttingenTammannstraße 237077GöttingenGermany
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Kreyenschmidt F, Eisele NF, Hevelke V, Rahrt R, Kreyenschmidt AK, Koszinowski K. In‐Situ Analysis of Anionic Coordination Polymerizations by Electrospray‐Ionization Mass Spectrometry. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202210211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Friedrich Kreyenschmidt
- Georg-August-Universität Göttingen: Georg-August-Universitat Gottingen Institut für Organische und Biomolekulare Chemie GERMANY
| | - Niklas F. Eisele
- Georg-August-Universitat Gottingen Institut für Organische und Biomolekulare Chemie GERMANY
| | - Valentin Hevelke
- Georg-August-Universitat Gottingen Institut für Organische und Biomolekulare Chemie GERMANY
| | - Rene Rahrt
- Georg-August-Universitat Gottingen Institut für Organische und Biomolekulare Chemie GERMANY
| | | | - Konrad Koszinowski
- Georg-August-Universitat Gottingen Institut für Organische und Biomolekulare Chemie Tammannstr. 2 37077 Göttingen GERMANY
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10
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Koszinowski K, Rahrt R. Anionic Dimers of Fluorinated Alcohols. J Am Soc Mass Spectrom 2022; 33:1411-1418. [PMID: 35609237 DOI: 10.1021/jasms.2c00070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Negative-ion mode electrospray ionization of solutions of ethanol (RF0OH), 2-fluoroethanol (RF1OH), 2,2-difluoroethanol (RF2OH), and/or 2,2,2-trifluoroethanol (RF3OH) produces anionic dimers of the types (RFnO)2H- and (RFnO)(RFn+1O)H-. The exchange reactions of these anionic dimers with the neutral alcohols are examined in a quadrupole-ion trap to extract kinetic data, from which the reaction Gibbs energies are obtained. In all cases, the formation of anionic dimers containing the more highly fluorinated alcohols is favored. Quantum chemical calculations confirm this trend and, besides affording structural data, also determine the dissociation energies of the anionic dimers. These dissociation energies are much higher than those of the corresponding neutral dimers and increase further for the more highly fluorinated alcohols due to the stronger hydrogen-bond donor ability of the latter. The present results on the interaction of individual alkoxide anions and neutral alcohol molecules contribute to a better understanding of the association of the fluorinated alcohols in solution.
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Affiliation(s)
- Konrad Koszinowski
- Universität Göttingen, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077 Göttingen, Germany
| | - Rene Rahrt
- Universität Göttingen, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077 Göttingen, Germany
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Abstract
We have applied a combination of tandem-mass spectrometry, quantum-chemical calculations, and statistical rate theory computations to examine the gas phase reactions between the trisarylzincate anions ArXZnPh2- (ArX = p-X-C6H4, X = NMe2, OMe, Me, H, F, and Cl) and 2,2,2-trifluoroethanol at T = 310 ± 20 K. The observed reactions bring about the protonation of one of the aryl anions, which is then released as the corresponding arene, while the formed alkoxide binds to the zinc center. The protonation is faster for the more electron-rich aryl groups and shows a linear Hammett plot if the rate constant for X = NMe2 is discarded from the analysis. Although the reactions are highly exothermic, they proceed only with relatively low efficiencies (0.1% ≤ φ ≤ 1.3%). According to the quantum-chemical calculations, this behavior can be ascribed to the reactions proceeding through a double-well potential with a tight transition structure located at the central barrier. Based on these potential energy surfaces, the statistical rate theory computations can reproduce the measured rate constants within factors of 2 to 8. A comparison of the protolysis of the trisarylzincates with that of the corresponding free aryl anions demonstrates how the coordination to the metal center not only stabilizes the carbanions energetically but also moderates their reactivity. Thus, our gas phase study contributes to a better understanding of the fundamentals of organometallic reactivity.
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Affiliation(s)
- Rene Rahrt
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, Göttingen 37077, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, Göttingen 37077, Germany
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12
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Auth T, Stein CJ, O'Hair RAJ, Koszinowski K. Origin of the different reactivity of the high-valent coinage-metal complexes [RCuIIIMe3]- and [RAgIIIMe3]- (R = allyl). Chemistry 2021; 28:e202103130. [PMID: 34773654 PMCID: PMC9304237 DOI: 10.1002/chem.202103130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Indexed: 11/27/2022]
Abstract
High‐valent tetraalkylcuprates(iii) and ‐argentates(iii) are key intermediates of copper‐ and silver‐mediated C−C coupling reactions. Here, we investigate the previously reported contrasting reactivity of [RMiiiMe3]− complexes (M=Cu, Ag and R=allyl) with energy‐dependent collision‐induced dissociation experiments, advanced quantum‐chemical calculations and kinetic computations. The gas‐phase fragmentation experiments confirmed the preferred formation of the [RCuMe]− anion upon collisional activation of the cuprate(iii) species, consistent with a homo‐coupling reaction, whereas the silver analogue primarily yielded [AgMe2]−, consistent with a cross‐coupling reaction. For both complexes, density functional theory calculations identified one mechanism for homo coupling and four different ones for cross coupling. Of these pathways, an unprecedented concerted outer‐sphere cross coupling is of particular interest, because it can explain the formation of [AgMe2]− from the argentate(iii) species. Remarkably, the different C−C coupling propensities of the two [RMiiiMe3]− complexes become only apparent when properly accounting for the multi‐configurational character of the wave function for the key transition state of [RAgMe3]−. Backed by the obtained detailed mechanistic insight for the gas‐phase reactions, we propose that the previously observed cross‐coupling reaction of the silver complex in solution proceeds via the outer‐sphere mechanism.
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Affiliation(s)
- Thomas Auth
- Georg-August-Universität Göttingen: Georg-August-Universitat Gottingen, Institut für Organische und Biomolekulare Chemie, GERMANY
| | - Christopher J Stein
- University of Duisburg-Essen: Universitat Duisburg-Essen, Faculty of Physics, Lotharstr. 1, 47057, Duisburg, GERMANY
| | - Richard A J O'Hair
- University of Melbourne, School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, AUSTRALIA
| | - Konrad Koszinowski
- Georg-August-Universität Göttingen: Georg-August-Universitat Gottingen, Institut für Organische und Biomolekulare Chemie, GERMANY
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13
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Auth T, Grabarics M, Schlangen M, Pagel K, Koszinowski K. Modular Ion Mobility Calibrants for Organometallic Anions Based on Tetraorganylborate Salts. Anal Chem 2021; 93:9797-9807. [PMID: 34227799 DOI: 10.1021/acs.analchem.1c01333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Organometallics are widely used in catalysis and synthesis. Their analysis relies heavily on mass spectrometric methods, among which traveling-wave ion mobility spectrometry (TWIMS) has gained increasing importance. Collision cross sections (CCS) obtainable by TWIMS significantly aid the structural characterization of ions in the gas phase, but for organometallics, their accuracy has been limited by the lack of appropriate calibrants. Here, we propose tetraorganylborates and their alkali-metal bound oligomers [Mn-1(BR4)n]- (M = Li, Na, K, Rb, Cs; R = aryl, Et; n = 1-6) as calibrants for electrospray ionization (ESI) TWIMS. These species chemically resemble typical organometallics and readily form upon negative-ion mode ESI of solutions of alkali-metal tetraorganylborates. By combining different tetraorganylborate salts, we have generated a large number of anions in a modular manner and determined their CCS values by drift-tube ion mobility spectrometry (DTIMS) (DTCCSHe = 81-585, DTCCSN2 = 130-704 Å2). In proof-of-concept experiments, we then applied these DTCCS values to the calibration of a TWIMS instrument and analyzed phenylcuprate and argentate anions, [Lin-1MnPh2n]- and [MnPhn+1]- (M = Cu, Ag), as prototypical reactive organometallics. The TWCCSN2 values derived from TWIMS measurements are in excellent agreement with those determined by DTIMS (<2% relative difference), demonstrating the effectiveness of the proposed calibration scheme. Moreover, we used theoretical methods to predict the structures and CCS values of the anions considered. These predictions are in good agreement with the experimental results and give further insight into the trends governing the assembly of tetraorganylborate, cuprate, and argentate oligomers.
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Affiliation(s)
- Thomas Auth
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, Göttingen 37077, Germany
| | - Márkó Grabarics
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, Berlin 14195, Germany.,Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Molekülphysik, Faradayweg 4-6, Berlin 14195, Germany
| | - Maria Schlangen
- Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 115, Berlin 10623, Germany
| | - Kevin Pagel
- Institut für Chemie und Biochemie, Freie Universität Berlin, Arnimallee 22, Berlin 14195, Germany.,Fritz-Haber-Institut der Max-Planck-Gesellschaft, Abteilung Molekülphysik, Faradayweg 4-6, Berlin 14195, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, Göttingen 37077, Germany
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Daly S, Weske S, Mravak A, Krstić M, Kulesza A, Antoine R, Bonačić-Koutecký V, Dugourd P, Koszinowski K, O’Hair RAJ. Phenyl argentate aggregates [AgnPhn+1]− (n = 2–8): Models for the self-assembly of atom-precise polynuclear organometallics. J Chem Phys 2021; 154:224301. [DOI: 10.1063/5.0052697] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- Steven Daly
- Institut Lumière Matière, Université Claude Bernard Lyon 1, CNRS UMR, 5306 Lyon, France
| | - Sebastian Weske
- Institute of Organic and Biomolecular Chemistry, Georg-August-University Göttingen, Göttingen, Germany
| | - Antonija Mravak
- Center of Excellence for Science and Technology-Integration of Mediterranean Region (STIM), Faculty of Science, University of Split, Ruđera Boškovića 33, Split 21000, Croatia
| | - Marjan Krstić
- Center of Excellence for Science and Technology-Integration of Mediterranean Region (STIM), Faculty of Science, University of Split, Ruđera Boškovića 33, Split 21000, Croatia
| | - Alexander Kulesza
- Institut Lumière Matière, Université Claude Bernard Lyon 1, CNRS UMR, 5306 Lyon, France
| | - Rodolphe Antoine
- Institut Lumière Matière, Université Claude Bernard Lyon 1, CNRS UMR, 5306 Lyon, France
| | - Vlasta Bonačić-Koutecký
- Center of Excellence for Science and Technology-Integration of Mediterranean Region (STIM), Faculty of Science, University of Split, Ruđera Boškovića 33, Split 21000, Croatia
- Interdisciplinary Center for Advanced Science and Technology (ICAST) at University of Split, Meštrovićevo šetalište 45, Split 21000, Croatia
- Chemistry Department Humboldt, University of Berlin, Brook-Taylor-Straße 2, Berlin 12489, Germany
| | - Philippe Dugourd
- Institut Lumière Matière, Université Claude Bernard Lyon 1, CNRS UMR, 5306 Lyon, France
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular Chemistry, Georg-August-University Göttingen, Göttingen, Germany
| | - Richard A. J. O’Hair
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Rd., Parkville, Victoria 3010, Australia
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15
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Deuker M, Yang Y, O’Hair RAJ, Koszinowski K. Tetraorganylargentate(III) Complexes: Key Intermediates in Silver-Mediated Cross-Coupling Reactions. Organometallics 2021. [DOI: 10.1021/acs.organomet.1c00118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Marius Deuker
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Yang Yang
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
| | - Richard A. J. O’Hair
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
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16
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Abstract
We propose electrospray-ionization (ESI) mass spectrometry as a robust and powerful method for the in situ analysis of carbanions. ESI mass spectrometry selectively probes the charged components of the sampled solution and, thus, is ideally suited for the detection of free carbanions. We demonstrate the potential of this method by analyzing acetonitrile solutions of 15 different carbon acids AH, whose acidities cover a range of 11.1 ≤ pKa(DMSO) ≤ 29.5. After treatment with KOtBu as a strong base, all but the two least acidic compounds were successfully detected as free carbanions A- and/or as potassium-bound aggregates [Kn-1An]-. The association equilibria can be shifted toward smaller aggregates and free carbanions by the addition of the crown ether 18-crown-6, which facilitates the evaluation of the mass spectra. When KOtBu was replaced by other bases (LiOH, LiNiPr2, NaH, NaOH, KOH, NBu4OH) or when tetrahydrofuran or methanol was used as a solvent, carbanions were also successfully observed. For further demonstrating the utility of the proposed method, we applied it to the analysis of the Michael addition of deprotonated dimedone to butenone. ESI mass spectrometry allowed us to follow the decrease of the reactant carbanion and the buildup of the product carbanion in time.
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Affiliation(s)
- Niklas F Eisele
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
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17
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Kabata Glowacki S, Koszinowski K, Hübner D, Frauendorf H, Vana P, Diederichsen U. Supramolecular Self-Assembly of β 3 -Peptides Mediated by Janus-Type Recognition Units. Chemistry 2020; 26:12145-12149. [PMID: 32621556 PMCID: PMC7539953 DOI: 10.1002/chem.202003107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Indexed: 01/18/2023]
Abstract
To gain mechanistic insights, natural systems with biochemical relevance are inspiring for the creation of new biomimetics with unique properties and functions. Despite progress in rational design and protein engineering, folding and intramolecular organization of individual components into supramolecular structures remains challenging and requires controlled methods. Foldamers, such as β-peptides, are structurally well defined with rigid conformations and suitable for the specific arrangement of recognition units. Herein, we show the molecular arrangement and aggregation of β3 -peptides into a hexameric helix bundle. For this purpose, β-amino acid side chains were modified with cyanuric acid and triamino-s-triazine as complementary recognition units. The pre-organization of the β3 -peptides leads these Janus molecule pairs into a hexameric arrangement and a defined rosette nanotube by stacking. The helical conformation of the subunits was indicated by circular dichroism spectroscopy, while the supramolecular arrangement was detected by dynamic light scattering and confirmed by high-resolution electrospray ionization mass spectrometry (ESI-HRMS).
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Affiliation(s)
- Selda Kabata Glowacki
- Institute of Organic and Biomolecular ChemistryGeorg-August-University GöttingenTammannstrasse 237077GöttingenGermany
- Center for Biostructural Imaging of Neurodegeneration (cfBIN)University Medical Center Göttingenvon-Sieboldstrasse 3a37075GöttingenGermany
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular ChemistryGeorg-August-University GöttingenTammannstrasse 237077GöttingenGermany
| | - Dennis Hübner
- Institute of Physical ChemistryGeorg-August-University GöttingenTammannstrasse 637077GöttingenGermany
| | - Holm Frauendorf
- Institute of Organic and Biomolecular ChemistryGeorg-August-University GöttingenTammannstrasse 237077GöttingenGermany
| | - Philipp Vana
- Institute of Physical ChemistryGeorg-August-University GöttingenTammannstrasse 637077GöttingenGermany
| | - Ulf Diederichsen
- Institute of Organic and Biomolecular ChemistryGeorg-August-University GöttingenTammannstrasse 237077GöttingenGermany
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18
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Kolter M, Koszinowski K. Second Comes First: Switching Elementary Steps in Palladium-Catalyzed Cross-Coupling Reactions. Chemistry 2020; 26:12212-12218. [PMID: 32428266 PMCID: PMC7540703 DOI: 10.1002/chem.202001041] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 05/11/2020] [Indexed: 12/13/2022]
Abstract
The electron-poor palladium(0) complex L3 Pd (L=tris[3,5-bis(trifluoromethyl)phenyl]phosphine) reacts with Grignard reagents RMgX and organolithium compounds RLi via transmetalation to furnish the anionic organopalladates [L2 PdR]- , as shown by negative-ion mode electrospray-ionization mass spectrometry. These palladates undergo oxidative additions of organyl halides R'X (or related SN 2-type reactions) followed by further transmetalation. Gas-phase fragmentation of the resulting heteroleptic palladate(II) complexes results in the reductive elimination of the cross-coupling products RR'. This reaction sequence corresponds to a catalytic cycle, in which the order of the elementary steps of transmetalation and oxidative addition is switched relative to that of palladium-catalyzed cross-coupling reactions proceeding via neutral intermediates. An attractive feature of the palladate-based catalytic system is its ability to mediate challenging alkyl-alkyl coupling reactions. However, the poor stability of the phosphine ligand L against decomposition reactions has so far prevented its successful use in practical applications.
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Affiliation(s)
- Marlene Kolter
- Institut für Organische und Biomolekulare ChemieGeorg-August-Universität GöttingenTammannstraße 237077GöttingenGermany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare ChemieGeorg-August-Universität GöttingenTammannstraße 237077GöttingenGermany
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19
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Affiliation(s)
- Thomas Auth
- Insitut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Konrad Koszinowski
- Insitut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Richard A. J. O’Hair
- Insitut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
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20
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Koszinowski K, Auth T. Modulation of Gas-Phase Lithium Cation Basicities by Microsolvation. J Am Soc Mass Spectrom 2019; 30:1857-1866. [PMID: 31502224 DOI: 10.1007/s13361-019-02312-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 08/12/2019] [Accepted: 08/12/2019] [Indexed: 06/10/2023]
Abstract
In contrast to the extensive knowledge of lithium cation affinities and basicities, the thermochemistry of microsolvated lithium cations is much less explored. Here, we determine the relative stabilities of Li(A,B)n+ complexes, n = 2 and 3, by monitoring their gas-phase reactions with A and B substrate molecules, A/B = Me2O, Et2O, tetrahydrofuran, and MeCN, in a three-dimensional quadrupole-ion trap mass spectrometer. Kinetic analysis of the observed ligand displacement reactions affords equilibrium constants, which are then converted into Gibbs reaction energies. In addition, we use high-level quantum chemical calculations to predict the structures and sequential ligand dissociation energies of the homoleptic Li(A)n+ complexes, n = 1-3. As expected, the ligands dissociate more easily from complexes in higher coordination states. However, the very nature of the ligand also matters. Ligands with different steric demands can, thus, invert their relative Li+ affinities depending on the coordination state of the metal center. This finding shows that microsolvation of Li+ can result in specific effects, which are not recognized if the analysis takes into account only simple lithium cation affinities and basicities.
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Affiliation(s)
- Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany.
| | - Thomas Auth
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
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21
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O'Hair RAJ, Roithová J, Koszinowski K. A Focus Honoring Helmut Schwarz's Election to the National Academy of Sciences : An Appreciation for and an Interview with Professor Helmut Schwarz. J Am Soc Mass Spectrom 2019; 30:1825-1827. [PMID: 31429051 DOI: 10.1007/s13361-019-02293-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Affiliation(s)
- Richard A J O'Hair
- School of Chemistry Bio21 Institute, The University of Melbourne,, Building 102, 30 Flemington Road, Melbourne, Victoria, 3010, Australia.
| | - Jana Roithová
- Radboud University Nijmegen, Institute for Molecules and Materials Department of Spectroscopy and Catalysis, Heyendaalseweg 135, 6525 AJ, Nijmegen, Netherlands
| | - Konrad Koszinowski
- Insitut für Organische und Biomolekulare Chemie, Universität Göttingen Institut für Organische und Biomolekulare Chemie, Tammannstraße 2, 37077, Göttingen, Germany
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22
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Kolter M, Koszinowski K. Formation of Transient Anionic Metal Clusters in Palladium/Diene-Catalyzed Cross-Coupling Reactions. Chemistry 2019; 25:13376-13384. [PMID: 31335999 PMCID: PMC7687115 DOI: 10.1002/chem.201902610] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 07/11/2019] [Indexed: 12/30/2022]
Abstract
Despite their considerable practical value, palladium/1,3‐diene‐catalyzed cross‐coupling reactions between Grignard reagents RMgCl and alkyl halides AlkylX remain mechanistically poorly understood. Herein, we probe the intermediates formed in these reactions by a combination of electrospray‐ionization mass spectrometry, UV/Vis spectroscopy, and NMR spectroscopy. According to our results and in line with previous hypotheses, the first step of the catalytic cycle brings about transmetalation to afford organopalladate anions. These organopalladate anions apparently undergo SN2‐type reactions with the AlkylX coupling partner. The resulting neutral complexes then release the cross‐coupling products by reductive elimination. In gas‐phase fragmentation experiments, the occurrence of reductive eliminations was observed for anionic analogues of the neutral complexes. Although the actual catalytic cycle is supposed to involve chiefly mononuclear palladium species, anionic palladium nanoclusters [PdnR(DE)n]−, (n=2, 4, 6; DE=diene) were also observed. At short reaction times, the dinuclear complexes usually predominated, whereas at longer times the tetra‐ and hexanuclear clusters became relatively more abundant. In parallel, the formation of palladium black pointed to continued aggregation processes. Thus, the present study directly shows dynamic behavior of the palladium/diene catalyst system and degradation of the active catalyst with increasing reaction time.
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Affiliation(s)
- Marlene Kolter
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany
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23
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Rahrt R, Auth T, Demireva M, Armentrout PB, Koszinowski K. Benzhydrylpyridinium Ions: A New Class of Thermometer Ions for the Characterization of Electrospray-Ionization Mass Spectrometers. Anal Chem 2019; 91:11703-11711. [DOI: 10.1021/acs.analchem.9b02257] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Rene Rahrt
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Thomas Auth
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
| | - Maria Demireva
- Department of Chemistry, University of Utah, 315 S. 1400 E., Salt Lake City, Utah 84112, United States
| | - P. B. Armentrout
- Department of Chemistry, University of Utah, 315 S. 1400 E., Salt Lake City, Utah 84112, United States
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
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24
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Sandl S, Maier TM, van Leest NP, Kröncke S, Chakraborty U, Demeshko S, Koszinowski K, de Bruin B, Meyer F, Bodensteiner M, Herrmann C, Wolf R, Jacobi von Wangelin A. Cobalt-Catalyzed Hydrogenations via Olefin Cobaltate and Hydride Intermediates. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01584] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sebastian Sandl
- Department of Chemistry, University of Hamburg, Martin Luther King Pl 6, 20146 Hamburg, Germany
| | - Thomas M. Maier
- Institute of Inorganic Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Nicolaas P. van Leest
- van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Susanne Kröncke
- Department of Chemistry, University of Hamburg, Martin Luther King Pl 6, 20146 Hamburg, Germany
| | - Uttam Chakraborty
- Department of Chemistry, University of Hamburg, Martin Luther King Pl 6, 20146 Hamburg, Germany
| | - Serhiy Demeshko
- Institute of Inorganic Chemistry, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular Chemistry, Universität Göttingen, Tammannstrasse 2, 37077 Göttingen, Germany
| | - Bas de Bruin
- van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Franc Meyer
- Institute of Inorganic Chemistry, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany
| | - Michael Bodensteiner
- Institute of Inorganic Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Carmen Herrmann
- Department of Chemistry, University of Hamburg, Martin Luther King Pl 6, 20146 Hamburg, Germany
| | - Robert Wolf
- Institute of Inorganic Chemistry, University of Regensburg, 93040 Regensburg, Germany
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25
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Abstract
>The combination of CoCl2 with bidentate phosphines is known to catalyze challenging cross-coupling and Heck-type reactions, but the mechanisms of these valuable transformations have not been established. Here, we use electrospray-ionization mass spectrometry to intercept the species formed in these reactions. Our results indicate that a sequence of transmetalation, reductive elimination, and redox disproportionation convert the cobalt(II) precatalyst into low-valent cobalt complexes. These species readily transfer single electrons to alkyl bromides, which thereupon dissociate into alkyl radicals and Br- . In cross-coupling reactions, the alkyl radicals add to the cobalt catalyst to form observable heteroleptic complexes, which release the coupling products through reductive eliminations. In the Heck-type reactions, the low abundance of newly formed ionic species renders the analysis more difficult. Nonetheless, our results also point to the occurrence of single-electron transfer processes and the involvement of radicals in these transformations.
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Affiliation(s)
- Friedrich Kreyenschmidt
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Selim E Meurer
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
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26
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Parchomyk T, Koszinowski K. Substitution reactions of gaseous ions in a three-dimensional quadrupole ion trap. J Mass Spectrom 2019; 54:81-87. [PMID: 30445664 DOI: 10.1002/jms.4313] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 06/09/2023]
Abstract
Substitution reactions between gaseous ions and neutral substrate molecules are of ongoing high interest. To investigate these processes in a qualitative and quantitative manner, we have constructed a device, with which a defined amount of a volatile substrate can be mixed with a defined amount of helium gas and added into a three-dimensional quadrupole ion trap. From the known inner volume of the device, the known ratio nsubstrate :nHe of the mixture, and the determined absolute partial pressure of helium in the ion trap, we can derive the partial pressure of the substrate in the ion trap and, thus, convert the directly observable pseudo-first-order rate constants of the substitution reactions into absolute bimolecular rate constants. We have tested the device by investigating a series of SN 2 reactions of Br- and CF3 CH2 O- anions as well as ligand exchange reactions of ligated Na+ cations. As the obtained results suggest, the described device makes it possible to determine the bimolecular rate constants of substitution reactions as well as other ion-molecule reactions with satisfactory accuracy and reliability.
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Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
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27
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Loup J, Parchomyk T, Lülf S, Demeshko S, Meyer F, Koszinowski K, Ackermann L. Mössbauer and mass spectrometry support for iron(ii) catalysts in enantioselective C–H activation. Dalton Trans 2019; 48:5135-5139. [DOI: 10.1039/c9dt00705a] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A combination of electrospray-ionization mass spectrometry and Mössbauer spectroscopy was used to investigate the species generated in situ in highly enantioselective Fe/NHC-catalyzed C–H alkylations.
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Affiliation(s)
- Joachim Loup
- Institut für Organische und Biomolekulare Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
| | - Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
| | - Stefan Lülf
- Institut für Organische und Biomolekulare Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
| | - Serhiy Demeshko
- Institut für Anorganische Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
| | - Franc Meyer
- Institut für Anorganische Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
| | - Lutz Ackermann
- Institut für Organische und Biomolekulare Chemie
- Universität Göttingen
- 37077 Göttingen
- Germany
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28
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Affiliation(s)
- Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, Göttingen 37077, Germany
| | - David S. Stephenson
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, München 81377, Germany
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29
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Parchomyk T, Koszinowski K. Electronic and Steric Effects on the Reductive Elimination of Anionic Arylferrate(III) Complexes. Chemistry 2018; 24:16342-16347. [PMID: 29969518 DOI: 10.1002/chem.201801003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Indexed: 11/11/2022]
Abstract
Arylferrate(III) complexes Ph3 FeR- (R=para- and ortho-substituted aryl) are proposed as model systems for the in-depth investigation of reductive eliminations from organoiron(III) species. Electrospray ionization transfers the arylferrate complexes prepared in situ from solution into the gas phase, where mass selection ensures a well-defined population of reactant ions. Upon gas-phase fragmentation, the arylferrate complexes undergo reductive elimination of the cross-coupling product PhR as well as the homo-coupling product Ph2 . The measured branching ratios between the two competing reaction channels are used to construct a Hammett plot, which shows that electron-donating aryl groups R favor the formation of the cross-coupling product. In this way, the complexes avoid the build-up of too much electron density at the iron center during the reductive elimination. ortho Substitution in R increases the fraction of the homo-coupling product, presumably by hindering the approach between the two aryl groups participating in the reductive elimination. The obtained mechanistic insight substantially advances our understanding of one of the central elementary steps of transition-metal-catalyzed cross-coupling reactions.
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Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
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30
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Abstract
We have applied a combination of electrospray-ionization mass spectrometry, electrical conductivity measurements, and Mössbauer spectroscopy to identify and characterize the organoferrate species R nFe m- formed upon the transmetalation of iron precursors (Fe(acac)3, FeCl3, FeCl2, Fe(OAc)2) with Grignard reagents RMgX (R = Me, Et, Bu, Hex, Oct, Dec, Me3SiCH2, Bn, Ph, Mes, 3,5-(CF3)2-C6H3; X = Cl, Br) in tetrahydrofuran. The observed organoferrates show a large variety in their aggregation (1 ≤ m ≤ 8) and oxidation states (I to IV), which are chiefly determined by the nature of their organyl groups R. In numerous cases, the addition of a bidentate amine or phosphine changes the distributions of organoferrates and affects their stability. Besides undergoing efficient intermolecular exchange processes, several of the probed organoferrates react with organyl (pseudo)halides R'X (R' = Et, iPr, Bu, Ph, p-Tol; X = Cl, Br, I, OTf) to afford heteroleptic complexes of the type R3FeR'-. Gas-phase fragmentation of most of these complexes results in reductive eliminations of the coupling products RR' (or, alternatively, of R2). This finding indicates that iron-catalyzed cross-coupling reactions may proceed via such heteroleptic organoferrates R3FeR'- as intermediates. Gas-phase fragmentation of other organoferrate complexes leads to β-hydrogen eliminations, the loss of arenes, and the expulsion of organyl radicals. The operation of both one- and two-electron processes is consistent with previous observations and contributes to the formidable complexity of organoiron chemistry.
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Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie , Universität Göttingen , Tammannstraße 2 , 37077 Göttingen , Germany
| | - Serhiy Demeshko
- Institut für Anorganische Chemie , Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany
| | - Franc Meyer
- Institut für Anorganische Chemie , Universität Göttingen , Tammannstraße 4 , 37077 Göttingen , Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie , Universität Göttingen , Tammannstraße 2 , 37077 Göttingen , Germany
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31
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Weske S, Hardin RA, Auth T, O'Hair RAJ, Koszinowski K, Ogle CA. Argentate(i) and (iii) complexes as intermediates in silver-mediated cross-coupling reactions. Chem Commun (Camb) 2018; 54:5086-5089. [PMID: 29708564 DOI: 10.1039/c8cc01707g] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite the potential of silver to mediate synthetically valuable cross-coupling reactions, the operating mechanisms have remained unknown. Here, we use a combination of rapid-injection NMR spectroscopy, electrospray-ionization mass spectrometry, and quantum chemical calculations to demonstrate that these transformations involve argentate(i) and (iii) complexes as key intermediates.
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Affiliation(s)
- Sebastian Weske
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany.
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32
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Kreyenschmidt F, Koszinowski K. Low-Valent Ate Complexes Formed in Cobalt-Catalyzed Cross-Coupling Reactions with 1,3-Dienes as Additives. Chemistry 2017; 24:1168-1177. [PMID: 29110364 DOI: 10.1002/chem.201704547] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Indexed: 12/23/2022]
Abstract
The combination of CoCl2 and 1,3-dienes is known to catalyze challenging alkyl-alkyl cross-coupling reactions between Grignard reagents and alkyl halides, but the mechanism of these valuable transformations remains speculative. Herein, electrospray-ionization mass spectrometry is used to identify and characterize the elusive intermediates of these and related reactions. The vast majority of detected species contain low-valent cobalt(I) centers and diene molecules. Charge tagging, deuterium labeling, and gas-phase fragmentation experiments elucidate the likely origin of these species and show that the diene not only binds to Co as a π ligand, but also undergoes migratory insertion reactions into Co-H and Co-R bonds. The resulting species have a strong tendency to form anionic cobalt(I) ate complexes, the superior nucleophilicity of which should render them highly reactive toward electrophilic substrates and, thus, presumably is the key to the high catalytic efficiency of the system under investigation. Upon the reaction of the in situ formed cobalt(I) ate complexes with organyl halides, only the final cross-coupling product could be detected, but no cobalt(III) species. This finding implies that this reaction step proceeds in a direct manner without any intermediate or, alternatively, that it involves an intermediate with a very short lifetime.
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Affiliation(s)
- Friedrich Kreyenschmidt
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
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33
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Ortgies S, Rieger R, Rode K, Koszinowski K, Kind J, Thiele CM, Rehbein J, Breder A. Mechanistic and Synthetic Investigations on the Dual Selenium-π-Acid/Photoredox Catalysis in the Context of the Aerobic Dehydrogenative Lactonization of Alkenoic Acids. ACS Catal 2017. [DOI: 10.1021/acscatal.7b02729] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stefan Ortgies
- Institut für
Organische und Biomolekulare Chemie, Georg-August-Universität, Tammannstrasse 2, 37077 Göttingen, Germany
| | - Rene Rieger
- Institut für
Organische und Biomolekulare Chemie, Georg-August-Universität, Tammannstrasse 2, 37077 Göttingen, Germany
| | - Katharina Rode
- Institut für
Organische und Biomolekulare Chemie, Georg-August-Universität, Tammannstrasse 2, 37077 Göttingen, Germany
| | - Konrad Koszinowski
- Institut für
Organische und Biomolekulare Chemie, Georg-August-Universität, Tammannstrasse 2, 37077 Göttingen, Germany
| | - Jonas Kind
- Clemens-Schöpf-Institut für Organische
Chemie und Biochemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse
16, 64287 Darmstadt, Germany
| | - Christina M. Thiele
- Clemens-Schöpf-Institut für Organische
Chemie und Biochemie, Technische Universität Darmstadt, Alarich-Weiss-Strasse
16, 64287 Darmstadt, Germany
| | - Julia Rehbein
- Organische Chemie, Universität Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Alexander Breder
- Institut für
Organische und Biomolekulare Chemie, Georg-August-Universität, Tammannstrasse 2, 37077 Göttingen, Germany
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34
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Abstract
Palladium ate complexes are frequently invoked as important intermediates in Heck and cross-coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray-ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron-poor catalyst [L3 Pd] (L=tris[3,5-bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br- ions to afford the anionic, zero-valent ate complex [L3 PdBr]- . In contrast, more-electron-rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L3 Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the PdII ate complex [L2 Pd(Ar)I2 ]- .
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Affiliation(s)
- Marlene Kolter
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany
| | - Katharina Böck
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377, München, Germany
| | - Konstantin Karaghiosoff
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377, München, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany
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Affiliation(s)
- Marlene Kolter
- Institut für Organische und Biomolekulare Chemie; Universität Göttingen; Tammannstraße 2 37077 Göttingen Deutschland
| | - Katharina Böck
- Department Chemie; Ludwig-Maximilians-Universität München; Butenandtstraße 5-13 81377 München Deutschland
| | - Konstantin Karaghiosoff
- Department Chemie; Ludwig-Maximilians-Universität München; Butenandtstraße 5-13 81377 München Deutschland
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Universität Göttingen; Tammannstraße 2 37077 Göttingen Deutschland
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Abstract
Iron-catalyzed cross-coupling reactions provide a promising way to form new carbon–carbon bonds and build up molecular complexity. This short review presents recent advances in the synthetic application of these reactions as well as in the elucidation of their mechanism. It also highlights remaining problems and aims at pointing out ways toward possible remedies.1 Introduction2 Synthesis: Recent Accomplishments and Unsolved Problems2.1 Substrate Scope: Electrophiles2.2 Substrate Scope: Nucleophiles2.3 Catalyst Activity and Chemoselectivity2.4 Stereoselectivity2.5 Practical Aspects3 Mechanism: Recent Insights and Open Questions3.1 Transmetallation and Activation of the Iron Precatalyst3.2 Coupling via Oxidative Addition and Reductive Elimination3.3 Coupling via C–X Bond Homolysis and Radical Rebound3.4 Coupling via Bimolecular C–X Bond Homolysis3.5 Other Reactions of Organoiron Species with Electrophiles4 Toward Rational Reaction Improvement5 Conclusion
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Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie, Universität Göttingen
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37
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Büschelberger P, Gärtner D, Reyes‐Rodriguez E, Kreyenschmidt F, Koszinowski K, Jacobi von Wangelin A, Wolf R. Alkene Metalates as Hydrogenation Catalysts. Chemistry 2017; 23:3139-3151. [PMID: 28026060 PMCID: PMC5861671 DOI: 10.1002/chem.201605222] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Indexed: 11/09/2022]
Abstract
First-row transition-metal complexes hold great potential as catalysts for hydrogenations and related reductive reactions. Homo- and heteroleptic arene/alkene metalates(1-) (M=Co, Fe) are a structurally distinct catalyst class with good activities in hydrogenations of alkenes and alkynes. The first syntheses of the heteroleptic cobaltates [K([18]crown-6)][Co(η4 -cod)(η2 -styrene)2 ] (5) and [K([18]crown-6)][Co(η4 -dct)(η4 -cod)] (6), and the homoleptic complex [K(thf)2 ][Co(η4 -dct)2 ] (7; dct=dibenzo[a,e]cyclooctatetraene, cod=1,5-cyclooctadiene), are reported. For comparison, two cyclopentadienylferrates(1-) were synthesized according to literature procedures. The isolated and fully characterized monoanionic complexes were competent precatalysts in alkene hydrogenations under mild conditions (2 bar H2 , r.t., THF). Mechanistic studies by NMR spectroscopy, ESI mass spectrometry, and poisoning experiments documented the operation of a homogeneous mechanism, which was initiated by facile redox-neutral π-ligand exchange with the substrates followed by H2 activation. The substrate scope of the investigated precatalysts was also extended to polar substrates (ketones and imines).
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Affiliation(s)
- Philipp Büschelberger
- Institute of Inorganic ChemistryUniversity of RegensburgUniversitätsstr. 3193040RegensburgGermany
| | - Dominik Gärtner
- Institute of Organic ChemistryUniversity of Regensburg93040RegensburgGermany
| | | | - Friedrich Kreyenschmidt
- Institut für Organische und Biomolekulare ChemieGeorg-August-Universität GöttingenTammannstr. 237077GöttingenGermany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare ChemieGeorg-August-Universität GöttingenTammannstr. 237077GöttingenGermany
| | | | - Robert Wolf
- Institute of Inorganic ChemistryUniversity of RegensburgUniversitätsstr. 3193040RegensburgGermany
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Koszinowski K, Lissy F. ESI activity of Br⁻, BF₄⁻ , ClO₄⁻ and BPh₄⁻ anions in the presence of Li⁺ and NBu⁴⁺ counter-ions. J Mass Spectrom 2017; 52:144-151. [PMID: 28098404 DOI: 10.1002/jms.3911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 01/12/2017] [Accepted: 01/14/2017] [Indexed: 06/06/2023]
Abstract
To improve our understanding of the electrospray ionization (ESI) process, we have subjected equimolar mixtures of salts A+ X- (A+ = Li+ , NBu4+ ; X- = Br- , ClO4- , BF4- , BPh4- ) in different solvents (CH3 CN, tetrahydrofuran, CH3 OH, H2 O) to negative-ion mode ESI and analyzed the relative ESI activity of the different anionic model analytes. The ESI activity of the large and hydrophobic BPh4- ion greatly exceeds that of the smaller and more hydrophilic anions Br- , ClO4- and BF4- , which we ascribe to its higher surface activity. Moreover, the ESI activity of the anions is modulated by the action of the counter-ions and their different tendency toward ion pairing. The tendency toward ion pairing can be reduced by the addition of the chelating ligands 12-crown-4 and 2.2.1 cryptand and is, although to a smaller degree, further influenced by the variation of the solvent. Complementary electrical conductivity measurements afford additional information on the interactions of the ionic constituents of the sample solutions. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- K Koszinowski
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - F Lissy
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
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39
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Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstr. 2 37077 Göttingen Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstr. 2 37077 Göttingen Germany
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40
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Parchomyk T, Koszinowski K. Back Cover: Ate Complexes in Iron-Catalyzed Cross-Coupling Reactions (Chem. Eur. J. 44/2016). Chemistry 2016. [DOI: 10.1002/chem.201604265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstr. 2 37077 Göttingen Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstr. 2 37077 Göttingen Germany
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41
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Affiliation(s)
- Tobias Parchomyk
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstr. 2 37077 Göttingen Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstr. 2 37077 Göttingen Germany
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42
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Kolter M, Koszinowski K. Stability and Unimolecular Reactivity of Palladate(II) Complexes [L n PdR 3 ] - (L=Phosphine, R=Organyl, n=0 and 1). Chemistry 2016; 22:15744-15750. [PMID: 27717040 DOI: 10.1002/chem.201603431] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Indexed: 11/08/2022]
Abstract
The reduction of PdII precatalysts to catalytically active Pd0 species is a key step in many palladium-mediated cross-coupling reactions. Besides phosphines, the stoichiometrically used organometallic reagents can afford this reduction, but do so in a poorly understood way. To elucidate the mechanism of this reaction, we have treated solutions of Pd(OAc)2 and a phosphine ligand L in tetrahydrofuran with RMgCl (R=Ph, Bn, Bu) as well as other organometallic reagents. Analysis of these model systems by electrospray- ionization mass spectrometry found palladate(II) complexes [Ln PdR3 ]- (n=0 and 1), thus pointing to the occurrence of transmetallation reactions. Upon gas-phase fragmentation, the [Ln PdR3 ]- anions preferentially underwent a reductive elimination to yield Pd0 species. The sequence of the transmetallation and reductive elimination, thus, constitutes a feasible mechanism for the reduction of the Pd(OAc)2 precatalyst. Other species of interest observed include the PdIV complex [PdBn5 ]- , which did not fragment via a reductive elimination but lost BnH instead.
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Affiliation(s)
- Marlene Kolter
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077, Göttingen, Germany.
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43
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Putau A, Brand H, Koszinowski K. Intermediates Formed in the Reactions of Organocuprates with α,β-Unsaturated Nitriles. Chemistry 2016; 22:12868-76. [PMID: 27461093 DOI: 10.1002/chem.201602451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Indexed: 11/10/2022]
Abstract
Conjugate additions of organocuprates are of outstanding importance for organic synthesis. To improve our mechanistic understanding of these reactions, we have used electrospray ionization mass spectrometry for the identification of the ionic intermediates formed upon the treatment of LiCuR2 ⋅LiCN (R=Me, Bu, Ph) with a series of α,β-unsaturated nitriles. Acrylonitrile, the weakest Michael acceptor included, did not afford any detectable intermediates. Fumaronitrile (FN) yielded adducts of the type Lin-1 Cun R2n (FN)n (-) , n=1-3. When subjected to fragmentation in the gas phase, these adducts were not converted into the conjugate addition products, but re-dissociated into the reactants. In contrast, the reaction with 1,1-dicyanoethylene furnished the products of the conjugate addition without any observable intermediates. Tri- and tetracyanoethylene proved to be quite reactive as well. The presence of several cyano groups in these substrates opened up reaction pathways different from simple conjugate additions, however, and led to dimerization and substitution reactions. Moreover, the gas-phase fragmentation behavior of the species formed from these substrates indicated the occurrence of single-electron transfer processes. Additional quantum-chemical calculations provided insight into the structures and stabilities of the observed intermediates and their consecutive reactions.
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Affiliation(s)
- Aliaksei Putau
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Harald Brand
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany.
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44
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Abstract
Trifluoromethylation reactions have recently received increased attention because of the beneficial effect of the trifluoromethyl group on the pharmacological properties of numerous substances. A common method to introduce the trifluoromethyl group employs the Ruppert-Prakash reagent, that is, Si(CH3 )3 CF3 , together with a copper(I) halide. We have applied this method to the trifluoromethylation of aromatic alkynes and used electrospray-ionization mass spectrometry to investigate the mechanism of these reactions in tetrahydrofuran, dichloromethane, and acetonitrile as well as with and without added 1,10-phenanthroline. In the absence of the alkyne component, the homoleptic ate complexes [Cu(CF3 )2 ](-) and [Cu(CF3 )4 ](-) were observed. In the presence of the alkynes RH, the heteroleptic complexes [Cu(CF3 )3 R](-) were detected as well. Upon gas-phase fragmentation, these key intermediates released the cross-coupling products R-CF3 with perfect selectivity. Apparently, the [Cu(CF3 )3 R](-) complexes did not originate from homoleptic cuprate anions, but from unobservable neutral precursors. The present results moreover point to the involvement of oxygen as the oxidizing agent.
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Affiliation(s)
- Sebastian Weske
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammanstraße 2, 37077, Göttingen, Germany
| | - Ramona Schoop
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammanstraße 2, 37077, Göttingen, Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammanstraße 2, 37077, Göttingen, Germany.
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45
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Schnegelsberg C, Bachmann S, Kolter M, Auth T, John M, Stalke D, Koszinowski K. Frontispiece: Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl. Chemistry 2016. [DOI: 10.1002/chem.201682362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Christoph Schnegelsberg
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Sebastian Bachmann
- Institut für Anorganische Chemie; Georg-August-Universität Göttingen; Tammannstraße 4 37077 Göttingen Germany
| | - Marlene Kolter
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Thomas Auth
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Michael John
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie; Georg-August-Universität Göttingen; Tammannstraße 4 37077 Göttingen Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
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46
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Schnegelsberg C, Bachmann S, Kolter M, Auth T, John M, Stalke D, Koszinowski K. Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl. Chemistry 2016; 22:7752-62. [DOI: 10.1002/chem.201600699] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Christoph Schnegelsberg
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Sebastian Bachmann
- Institut für Anorganische Chemie; Georg-August-Universität Göttingen; Tammannstraße 4 37077 Göttingen Germany
| | - Marlene Kolter
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Thomas Auth
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Michael John
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie; Georg-August-Universität Göttingen; Tammannstraße 4 37077 Göttingen Germany
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Germany
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47
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Brouillet EV, Kennedy AR, Koszinowski K, McLellan R, Mulvey RE, Robertson SD. Exposing elusive cationic magnesium–chloro aggregates in aluminate complexes through donor control. Dalton Trans 2016; 45:5590-7. [DOI: 10.1039/c6dt00531d] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Judicious choice of Lewis donor provides control over the aggregation state of the [MgxCl2x−1]+ cation in a series of Mg battery relevant magnesium aluminates.
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Affiliation(s)
- Etienne V. Brouillet
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow
- UK
| | - Alan R. Kennedy
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow
- UK
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie
- Georg-August-Universität Göttingen
- 37077 Göttingen
- Germany
| | - Ross McLellan
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow
- UK
| | - Robert E. Mulvey
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow
- UK
| | - Stuart D. Robertson
- WestCHEM
- Department of Pure and Applied Chemistry
- University of Strathclyde
- Glasgow
- UK
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48
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Schnegelsberg C, Blümke TD, Koszinowski K. Which cations form upon CSI or ESI of solutions of Grignard reagents? J Mass Spectrom 2015; 50:1393-1395. [PMID: 26634973 DOI: 10.1002/jms.3710] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 09/21/2015] [Accepted: 09/21/2015] [Indexed: 06/05/2023]
Affiliation(s)
- Christoph Schnegelsberg
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
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49
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Schubert M, Franzmann P, Wünsche von Leupoldt A, Koszinowski K, Heinze K, Waldvogel SR. Überoxidation als Schlüsselschritt im Mechanismus der MoCl5
- vermittelten dehydrierenden Arenkupplung. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201508035] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Moritz Schubert
- Institut für Organische Chemie; Johannes Gutenberg-Universität Mainz; Duesbergweg 10-14 55128 Mainz Deutschland
| | - Peter Franzmann
- Institut für Organische Chemie; Johannes Gutenberg-Universität Mainz; Duesbergweg 10-14 55128 Mainz Deutschland
| | - Anica Wünsche von Leupoldt
- Institut für Anorganische und Analytische Chemie; Johannes Gutenberg-Universität Mainz; Duesbergweg 10-14 55128 Mainz Deutschland
| | - Konrad Koszinowski
- Institut für Organische und Biomolekulare Chemie; Georg-August-Universität Göttingen; Tammannstraße 2 37077 Göttingen Deutschland
| | - Katja Heinze
- Institut für Anorganische und Analytische Chemie; Johannes Gutenberg-Universität Mainz; Duesbergweg 10-14 55128 Mainz Deutschland
| | - Siegfried R. Waldvogel
- Institut für Organische Chemie; Johannes Gutenberg-Universität Mainz; Duesbergweg 10-14 55128 Mainz Deutschland
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50
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Schubert M, Franzmann P, Wünsche von Leupoldt A, Koszinowski K, Heinze K, Waldvogel SR. Over-Oxidation as the Key Step in the Mechanism of the MoCl5-Mediated Dehydrogenative Coupling of Arenes. Angew Chem Int Ed Engl 2015; 55:1156-9. [PMID: 26473303 DOI: 10.1002/anie.201508035] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Indexed: 01/12/2023]
Abstract
Molybdenum pentachloride is an unusually powerful reagent for the dehydrogenative coupling of arenes. Owing to the high reaction rate using MoCl5, several labile moieties are tolerated in this transformation. The mechanistic course of the reaction was controversially discussed although indications for a single electron transfer as the initial step were found recently. Herein, based on a combined study including synthetic investigations, electrochemical measurements, EPR spectroscopy, DFT calculations, and mass spectrometry, we deduct a highly consistent mechanistic scenario: MoCl5 acts as a one-electron oxidant in the absence of TiCl4 and as two-electron oxidant in the presence of TiCl4, but leads to an over-oxidized intermediate in both cases, which protects it from side reactions. In the course of aqueous work-up the reagent waste (Mo(III/IV) species) acts as reducing agent generating the desired organic C-C coupling product.
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Affiliation(s)
- Moritz Schubert
- Department of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Peter Franzmann
- Department of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Anica Wünsche von Leupoldt
- Department of Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Konrad Koszinowski
- Institute of Organic and Biomolecular Chemistry, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077, Göttingen, Germany.
| | - Katja Heinze
- Department of Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany.
| | - Siegfried R Waldvogel
- Department of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128, Mainz, Germany.
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