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Cramer HH, Pecoraro MV, Chirik PJ. Pyridine(diimine) Chromium η, 1η 3-Metallacycles as Precatalysts for Alkene-Diene [2 + 2] Cycloaddition. J Am Chem Soc 2025; 147:13688-13698. [PMID: 40215339 DOI: 10.1021/jacs.5c01182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/24/2025]
Abstract
The synthesis, characterization, and catalytic cycloaddition reactivity of aryl-substituted pyridine(diimine) (PDI) chromium ether complexes and alkene-diene derived metallacycles are described. The reduction of either (PDI)CrCl2 or (PDI)CrCl3 with sodium and catalytic amounts of naphthalene furnished the corresponding chromium THF or diethyl ether complexes. Exposure of the reduced chromium compounds to a mixture of butadiene and ethylene induced rapid oxidative cyclization and yielded isolable, thermally stable chromium η,1η3 trans-metallacycles. In the presence of pure butadiene, oxidative cyclization was also observed, and a η,1η3 diene-diene chromacycloheptane with vinyl substitution was isolated and crystallographically characterized. Reductive C(sp3)-C(sp3) elimination of the resulting vinylcyclobutane products was promoted by either one-electron oxidation or irradiation with visible light in the presence of diene or coordinating solvents such as THF. Under thermal catalytic conditions, the chromacycles converted butadiene and ethylene to a mixture of vinylcyclobutane arising from [2 + 2] cycloaddition and cis-1,4-hexadiene resulting from competitive hydrovinylation. Visible light irradiation at ambient temperature enabled selective catalytic [2 + 2] cycloaddition. Isotopic labeling studies with 13C-labeled ethylene established that the alkene-diene chromacycle is thermodynamically preferred over the diene-diene alternative and that both oxidative cyclization and reductive coupling steps are reversible. Visible light accelerated the reductive coupling step, while subsequent product displacement from the metal center occurs in the presence of excess diene.
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Affiliation(s)
- Hanna H Cramer
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Matthew V Pecoraro
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Souilah C, Jannuzzi SAV, Becker FJ, Demirbas D, Jenisch D, Ivlev S, Xie X, Peredkov S, Lichtenberg C, DeBeer S, Casitas A. Synthesis of Iron(IV) Alkynylide Complexes and Their Reactivity to Form 1,3-Diynes. Angew Chem Int Ed Engl 2025; 64:e202421222. [PMID: 39551703 DOI: 10.1002/anie.202421222] [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: 11/01/2024] [Revised: 11/14/2024] [Accepted: 11/14/2024] [Indexed: 11/19/2024]
Abstract
The isolation of thermally unstable and highly reactive organoiron(IV) complexes is a challenge for synthetic chemists. In particular, the number of examples where the C-based ligand is not part of the chelating ligand remains scarce. These compounds are of interest because they could pave the way to designing catalytic cycles of bond forming reactions proceeding via organoiron(IV) intermediates. Herein, we report the synthesis and characterization, including single-crystal X-ray diffraction, of a family of alkynylferrates(III) and Fe(IV) alkynylide complexes. The alkynylferrates(III) are formed by transmetalation of the Fe(III) precursor [(N3N')FeIII] (N3N'3- is tris(N-tert-butyldimethylsilyl-2-amidoethyl)amine) with lithium alkynylides, and their further one-electron oxidation enables the synthesis of the corresponding Fe(IV) alkynylides. The electronic structure of this family of organometallic Fe(III) and Fe(IV) complexes has been thoroughly investigated by spectroscopic methods (EPR, NMR, 57Fe Mössbauer, X-Ray absorption (XAS) and emission (XES) spectroscopies) and theoretical calculations. While alkynylferrates(III) are sluggish to engage into C-C bond forming processes, the Fe(IV) alkynylides react to afford 1,3-diynes at room temperature. A bimolecular reductive elimination from a bimetallic Fe(IV) intermediate to form the 1,3-diynes is proposed based on the mechanistic investigations performed.
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Affiliation(s)
- Charafa Souilah
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
| | - Sergio A V Jannuzzi
- Max Planck Institute for Chemical Energy Conversion (MPI CEC), Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Felix J Becker
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
| | - Derya Demirbas
- Max-Planck-Institut für Kohlenforschung (MPI KOFO), Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
| | - Daniel Jenisch
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
| | - Sergei Ivlev
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
| | - Xiulan Xie
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
| | - Sergey Peredkov
- Max Planck Institute for Chemical Energy Conversion (MPI CEC), Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Crispin Lichtenberg
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion (MPI CEC), Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Alicia Casitas
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany
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Li H, Fan M, Liu Q. Unveiling the Unique Reactivity of Anionic Mn(I) Complexes via Metal-Ligand Cooperation: Nucleophilic Attack on C(sp 3)-X Bonds. J Am Chem Soc 2024; 146:26649-26656. [PMID: 39295280 DOI: 10.1021/jacs.4c01683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/21/2024]
Abstract
Metal-ligand cooperation (MLC) has emerged as a pivotal strategy for the catalytic activation of small molecules within both synthetic and biological arenas. Leveraging this approach, a suite of potent catalytic reactions─encompassing hydrogenation, hydroelementation, and dehydrogenative processes─have been realized, with notable advances in manganese catalysis in recent years. However, the activation of alkyl halides by Mn complexes, which typically requires strong reductants to form Mn(-I) complexes that are incompatible with standard cross-coupling conditions, remains a significant challenge. This limitation underscores the urgent need to investigate alternative methods for activating C(sp3)-X bonds using higher valence state Mn complexes. In response to this challenge, we present the synthesis, characterization, and reactivity of a new anionic Mn(I) complex featuring a redox-active dianionic ligand that induces multiple MLC functionalities. We have discovered an innovative mechanism of MLC, characterized by a single ligand transferring two electrons to the metal center. This novel process facilitates an orbital-symmetry-allowed nucleophilic attack on C(sp3)-X bonds, preserving manganese's oxidative state at +1. To the best of our knowledge, this is the first instance where the MLC strategy via a two-electron transfer process has been utilized to execute an SN2 nucleophilic attack at a C(sp3)-X bond by a relatively electron-deficient metal center like Mn(I). Additionally, the dianionic ligand of the anionic Mn(I) complex exhibits ambident nucleophilicity by reacting with different electrophiles, further highlighting its versatile reactivity.
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Affiliation(s)
- Hengxu Li
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Mingjie Fan
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Qiang Liu
- Center of Basic Molecular Science, Department of Chemistry, Tsinghua University, Beijing 100084, China
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Zhang T, Pabst TP, Hoyt JM, Pecoraro MV, Chirik PJ. Mechanistic Studies and Identification of Catalyst Deactivation Pathways for Pyridine(diimine) Iron Catalyzed C(sp 2)-H Borylation. ACS Catal 2024; 14:13999-14011. [PMID: 39555381 PMCID: PMC11563351 DOI: 10.1021/acscatal.4c03744] [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] [Indexed: 11/19/2024]
Abstract
The synthesis and application of aryl-substituted pyridine(diimine) iron complexes (RPDI)FeCH3 to the catalytic borylation of heteroarenes under thermal conditions is described. Improvements in catalyst design and performance were guided by precatalyst activation studies, where investigations into stoichiometric reactivities of iron borohydride (4- t Bu- iPrPDI)Fe(H2BPin) and iron furyl (4- t Bu- iPrPDI)Fe(2-methylfuryl) complexes revealed facile C(sp2)-H activation and a slower and potentially turnover-limiting C(sp2)-B formation step. Formation of the flyover dimer, [(4- t Bu- iPrPDI)Fe]2 was identified as a catalyst deactivation pathway and formally iron(0) complexes were found to be inactive for borylation. The pyridine(diimine) iron borohydride, flyover dimer and furyl complexes were characterized by X-ray diffraction and their electronic structures determined by a combination of NMR, EPR, and Mössbauer spectroscopies corroborated by DFT calculations. The role of the redox-active pyridine(diimine) ligand in catalytic C-H borylation was also investigated.
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Affiliation(s)
- Tianyi Zhang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Tyler P Pabst
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Jordan M Hoyt
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Matthew V Pecoraro
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Nie C, Park C, Kim J, Chirik PJ. Nickel-Catalyzed C-C Activation of Vinylcyclobutane with Visible Light: Scope, Mechanism, and Application to Chemically Recyclable Polyolefins. J Am Chem Soc 2024; 146:24818-24831. [PMID: 39213587 DOI: 10.1021/jacs.4c04611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
N-heterocyclic carbene (NHC)-supported nickel complexes were investigated for the oxidative ring-opening of vinylcyclobutane (VCB) and photocatalytic activity. Addition of VCB to in situ generated [(NHC)Ni(0)] compounds furnished (NHC)Ni(VCB)2 that underwent oxidative addition and conversion to the corresponding Ni(II) alkyl, allyl-metallacycles. The (NHC)Ni(C6H10) metallacycles were isolated, characterized, and exhibited high thermal and chemical stability. Irradiation with visible light at ambient temperature produced a mixture of ethylene and 4-vinylcyclohexene and 1,5-cyclooctadiene, cycloaddition dimers of butadiene, arising from formal retro-[2 + 2] cycloaddition. A mixture of hexadiene products arising from β-H elimination from the metallacycle was also observed. Free ethylene also underwent a secondary reaction to form cyclopropane products through formal [2 + 1] cycloaddition. A series of sterically and electronically modified NHC ligands was evaluated to establish the structure-activity relationship governing the rate of photocatalytic conversion of VCB and the resulting product distribution. Isotopic labeling experiments, resting state analysis, and independent synthesis of a range of nickel bis(olefin) complexes provided insight into the mechanism of the reaction and origins of the organic product mixture. (NHC)Ni-catalysis was also applied toward the retro-[2 + 2] depolymerization of (1,n'-divinyl)-oligocyclobutane to butadiene dimers.
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Affiliation(s)
- Cherish Nie
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Chloe Park
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Junho Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Cramer HH, Duchemin C, Kovel CB, Kim J, Pecoraro MV, Chirik PJ. Ligand Field Sensitive Spin Acceleration in the Iron-Catalyzed [2 + 2] Cycloaddition of Unactivated Alkenes and Dienes. J Am Chem Soc 2024; 146:9947-9956. [PMID: 38537152 DOI: 10.1021/jacs.4c00591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
Redox-active pyridine(diimine) (PDI) iron catalysts promote the reversible [2 + 2] cycloaddition of alkenes and dienes to cyclobutane derivatives that have applications ranging from fuels to chemically recyclable polymers. Metallacycles were identified as key intermediates, and spin crossover from the singlet to the triplet surface was calculated to facilitate the reductive coupling step responsible for the formation of the four-membered ring. In this work, a series of sterically and electronically differentiated PDI ligands was studied for the [2 + 2] cycloaddition of ethylene and butadiene to vinylcyclobutane. Kinetic studies revealed that the fastest and slowest turnover were observed with equally electron-deficient supporting ligands that either feature phenyl-substituted imine carbon atoms (MeBPDI) or a pyrazine core (MePZDI). While the oxidative cyclization was comparatively slow for both catalysts, the rate of reductive coupling─determined by stoichiometric 13C2H4 labeling studies─correlated with the turnover frequencies. Two-state density functional theory studies and the distinct electronic structures of related (iPrBPDI) and (iPrPZDI) iron methyl complexes revealed significantly different ligand field strengths due to either diminished ligand σ-donation (MeBPDI) or promoted metal π-backbonding (MePZDI). Spin acceleration, leading to fast reductive coupling and catalytic turnover, was promoted in the case of the weaker ligand field and depends on both the nature and position of the electron-withdrawing group. This study provides strong evidence for the role of two-state reactivity in C(sp3)-C(sp3) bond formation and insights on how ligand design either promotes or inhibits spin acceleration in earth-abundant metal catalysis.
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Affiliation(s)
- Hanna H Cramer
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Coralie Duchemin
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Carli B Kovel
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Junho Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Matthew V Pecoraro
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Duchemin C, Kim J, Chirik PJ. CS-Symmetric Pyridine(diimine) Iron Methyl Complexes for Catalytic [2+2] Cycloaddition and Hydrovinylation: Metallacycle Geometry Determines Selectivity. JACS AU 2023; 3:2007-2024. [PMID: 37502155 PMCID: PMC10369671 DOI: 10.1021/jacsau.3c00229] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Revised: 06/17/2023] [Accepted: 06/20/2023] [Indexed: 07/29/2023]
Abstract
A series of CS-symmetric (aryl,alkyl)-substituted pyridine(dimine) iron methyl (CyARPDI)FeCH3 complexes have been prepared, characterized, and evaluated as precatalysts for the [2+2]-cycloaddition of butadiene and ethylene. Mixtures of vinylcyclobutane and (Z)-hexa-1,4-diene were observed in each case. By comparison, C2v-symmetric, arylated (PDI) iron catalysts are exclusively selective for reversible [2+2]-cycloaddition to yield vinylcyclobutane. The alteration in the chemoselectivity of the catalytic reaction was investigated through a combination of precatalyst stability studies, identification of catalytic resting state(s), and 2H and 13C isotopic labeling experiments. While replacement of an aryl-imine substituent with an N-alkyl group decreases the stability of the formally iron(0) dinitrogen and butadiene complexes, two diamagnetic metallacycles were identified as catalyst resting states. Deuterium labeling and NOESY/EXSY NMR experiments support 1,4-hexadiene arising from catalytic hydrovinylation involving reversible oxidative cyclization leading to accessible cis-metallacycle. Cyclobutane formation proceeds by irreversible C(sp3)-C(sp3) bond-forming reductive elimination from a trans-metallacycle. These studies provide key mechanistic understanding into the high selectivity of bis(arylated) pyridine(diimine) iron catalysts for [2+2]-cycloaddition, unique, thus far, to this class of iron catalysts.
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