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Khor CK, Calhoun LA, Neville JJ, Dyker CA. Experimental and Theoretical Predictors for Redox Potentials of Bispyridinylidene Electron Donors. Chemphyschem 2024; 25:e202400092. [PMID: 38743866 DOI: 10.1002/cphc.202400092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 05/10/2024] [Accepted: 05/13/2024] [Indexed: 05/16/2024]
Abstract
Bispyridinylidenes are neutral organic molecules capable of two-electron oxidation at a range of redox potentials that are widely tunable by choice of substituent, making them attractive as homogeneous organic reductants and active materials in redox flow batteries. In an effort to readily predict the redox potentials of this important class of compounds, we have developed correlations between the experimental redox potentials and both experimental and theoretical predictors. On the experimental side, we show that multinuclear NMR chemical shifts of related pyridinium ions correlate well with the redox potentials of bispyridinylidenes, with R2 and standard errors (S) reaching 0.9810 and 0.048 V, respectively, when the 13C (N-CH3) and 1H (ortho) chemical shifts are used together. Theoretical studies of the bispyridinylidenes and their doubly oxidized bipyridinium ions gave a range of predictively valuable equations at various levels of computational cost. This ranged from a simple model using only the EHOMO of the bispyridinylidenes (R2=0.9689; S=0.060 V), to a more computationally intensive model which include solvation effects for both redox states which gave the highest predictive value for all methods (R2=0.9958; S=0.022 V). This work will guide further studies of this important class of molecules.
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Affiliation(s)
- Chun Keat Khor
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, Canada, E3B 5 A3
| | - Larry A Calhoun
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, Canada, E3B 5 A3
| | - John J Neville
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, Canada, E3B 5 A3
| | - C Adam Dyker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, Canada, E3B 5 A3
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2
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Franzen JH, Wilm LFB, Rotering P, Wurst K, Seidl M, Dielmann F. Electron-rich pyridines with para-N-heterocyclic imine substituents: ligand properties and coordination to CO 2, SO 2, BCl 3 and Pd II complexes. Dalton Trans 2024; 53:11876-11883. [PMID: 38953467 DOI: 10.1039/d4dt01399a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/04/2024]
Abstract
Electron-rich pyridines with π donor groups at the para position play an important role as nucleophiles in organocatalysis, but their ligand properties and utilization in coordination chemistry have received little attention. Herein, we report the synthesis of two electron-rich pyridines 1 and 2 bearing N-heterocyclic imine groups at the para position and explore their coordination chemistry. Experimental and computational methods were used to assess the donor ability of the new pyridines showing that they are stronger donors than aminopyridines and guanidinyl pyridines, and that the nature of the N-heterocyclic backbone has a strong influence on the pyridine donor strength. Coordination compounds with Lewis acids including the CO2, SO2, BCl3 and PdII ions were synthesized and characterized. Despite the ambident character of the new pyridines, coordination preferentially occurs at the pyridine-N atom. Methyl transfer experiments reveal that 1 and 2 can act as demethylation reagents.
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Affiliation(s)
- Jonas H Franzen
- Institut für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Lukas F B Wilm
- Institut für Anorganische und Analytische Chemie, Universität Münster Corrensstrasse 30, 48149 Münster, Germany
| | - Philipp Rotering
- Institut für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Klaus Wurst
- Institut für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Michael Seidl
- Institut für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
| | - Fabian Dielmann
- Institut für Allgemeine, Anorganische und Theoretische Chemie, Leopold-Franzens-Universität Innsbruck, Innrain 80-82, 6020 Innsbruck, Austria.
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3
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Bieniek J, Nater DF, Eberwein SL, Schollmeyer D, Klein M, Waldvogel SR. Efficient and Sustainable Electrosynthesis of N-Sulfonyl Iminophosphoranes by the Dehydrogenative P-N Coupling Reaction. JACS AU 2024; 4:2188-2196. [PMID: 38938819 PMCID: PMC11200248 DOI: 10.1021/jacsau.4c00156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 03/31/2024] [Accepted: 04/03/2024] [Indexed: 06/29/2024]
Abstract
Iminophosphoranes are commonly used reagents in organic synthesis and are, therefore, of great interest. An efficient and sustainable iodide-mediated electrochemical synthesis of N-sulfonyl iminophosphoranes from readily available phosphines and sulfonamides is reported. This method features low amounts of supporting electrolytes, inexpensive electrode materials, a simple galvanostatic setup, and high conversion rates. The broad applicability could be demonstrated by synthesizing 20 examples in yields up to 90%, having diverse functional groups including chiral moieties and biologically relevant species. Furthermore, electrolysis was performed on a 20 g scale and could be run in repetitive mode by recycling the electrolyte, which illustrates the suitability for large-scale production. A reaction mechanism involving electrochemical mediation by the iodide-based supporting electrolyte is proposed, completely agreeing with all of the results.
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Affiliation(s)
- Jessica
C. Bieniek
- Department
of Chemistry, Johannes Gutenberg University
Mainz, Duesbergweg 10–14, 55128 Mainz, Germany
| | - Darryl F. Nater
- Department
of Chemistry, Johannes Gutenberg University
Mainz, Duesbergweg 10–14, 55128 Mainz, Germany
- Max-Planck-Institute
for Chemical Energy Conversion, Stiftstraße 34–36, 45470 Mülheim an der Ruhr, Germany
| | - Sara L. Eberwein
- Department
of Chemistry, Johannes Gutenberg University
Mainz, Duesbergweg 10–14, 55128 Mainz, Germany
| | - Dieter Schollmeyer
- Department
of Chemistry, Johannes Gutenberg University
Mainz, Duesbergweg 10–14, 55128 Mainz, Germany
| | - Martin Klein
- Department
of Chemistry, Johannes Gutenberg University
Mainz, Duesbergweg 10–14, 55128 Mainz, Germany
| | - Siegfried R. Waldvogel
- Department
of Chemistry, Johannes Gutenberg University
Mainz, Duesbergweg 10–14, 55128 Mainz, Germany
- Institute
of Biological and Chemical Systems—Functional Molecular Systems
(IBCS-FMS), Hermann-von-Helmholtz-Platz
1, 76344 Eggenstein-Leopoldshafen, Germany
- Max-Planck-Institute
for Chemical Energy Conversion, Stiftstraße 34–36, 45470 Mülheim an der Ruhr, Germany
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4
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Richard NA, Charlton GD, Dyker CA. Enhancing catalytic activity of pyridines via para-iminophosphorano substituents. Org Biomol Chem 2021; 19:9167-9171. [PMID: 34664050 DOI: 10.1039/d1ob01630j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four pyridines decorated with π-donating iminophosphorano substituents (R3PN-) in the 4-position were assessed as acylation catalysts. These catalysts display high sensitivity to the groups at phosphorus, with activities that are well correlated to the corresponding Hammett-type substituent constants (σp+), and can achieve superior activity over the most active dialkylamino-substituted pyridines. Iminophosphorano-substituted pyridines represent an easily accessible, tunable, and highly active class of nucleophilic organocatalysts.
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Affiliation(s)
- Nicholas A Richard
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada.
| | - Grant D Charlton
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada.
| | - C Adam Dyker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada.
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Frenette BL, Arsenault N, Walker SL, Decken A, Dyker CA. Bis(Iminophosphorano)-Substituted Pyridinium Ions and their Corresponding Bispyridinylidene Organic Electron Donors. Chemistry 2021; 27:8528-8536. [PMID: 33834560 DOI: 10.1002/chem.202100318] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Indexed: 12/22/2022]
Abstract
Optimized synthetic procedures for pyridinium ions featuring iminophosphorano (-N=PR3 ; R=Ph, Cy) π-donor substituents in the 2- and 4- positions are described. Crystallographic and theoretical studies reveal that the strongly donating substituents severely polarize the π-electrons of the pyridyl ring at the expense of aromaticity. Moreover, the pyridinium ions are readily deprotonated to generate powerful bispyridinylidene (BPY) organic electron donors. Electrochemical studies show exceptionally low redox potentials for the two-electron BPY/BPY2+ couples, ranging from -1.71 V vs the saturated calomel electrode for 3PhPh (with four Ph3 P=N- groups) to -1.85 V for 3CyCy (with four Cy3 P=N- groups). These new compounds represent the most reducing neutral organic electron donors (OEDs) currently known. Some preliminary reductions involving 3CyCy showed enhanced capability owing to its low redox potential, such as the thermally activated reduction of an aryl chloride, but purification challenges were often encountered.
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Affiliation(s)
- Brandon L Frenette
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Nadine Arsenault
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Sarah L Walker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - Andreas Decken
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
| | - C Adam Dyker
- Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3, Canada
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