1
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Zhang ZJ, Jacob N, Bhatia S, Boos P, Chen X, DeMuth JC, Messinis AM, Jei BB, Oliveira JCA, Radović A, Neidig ML, Wencel-Delord J, Ackermann L. Iron-catalyzed stereoselective C-H alkylation for simultaneous construction of C-N axial and C-central chirality. Nat Commun 2024; 15:3503. [PMID: 38664372 PMCID: PMC11045758 DOI: 10.1038/s41467-024-47589-7] [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: 06/05/2023] [Accepted: 04/04/2024] [Indexed: 04/28/2024] Open
Abstract
The assembly of chiral molecules with multiple stereogenic elements is challenging, and, despite of indisputable advances, largely limited to toxic, cost-intensive and precious metal catalysts. In sharp contrast, we herein disclose a versatile C-H alkylation using a non-toxic, low-cost iron catalyst for the synthesis of substituted indoles with two chiral elements. The key for achieving excellent diastereo- and enantioselectivity was substitution on a chiral N-heterocyclic carbene ligand providing steric hindrance and extra represented by noncovalent interaction for the concomitant generation of C-N axial chirality and C-stereogenic center. Experimental and computational mechanistic studies have unraveled the origin of the catalytic efficacy and stereoselectivity.
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Affiliation(s)
- Zi-Jing Zhang
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany
| | - Nicolas Jacob
- Laboratoire d'Innovation Moléculaire et Applications (UMR CNRS 7042), Université de Strasbourg/Université de Haute-Alsace, ECPM, 67087, Strasbourg, France
| | - Shilpa Bhatia
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - Philipp Boos
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany
| | - Xinran Chen
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany
- Department of Chemistry, Zhejiang University, 310027, Hangzhou, China
| | - Joshua C DeMuth
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - Antonis M Messinis
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany
| | - Becky Bongsuiru Jei
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany
| | - João C A Oliveira
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany
| | - Aleksa Radović
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - Michael L Neidig
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK.
| | - Joanna Wencel-Delord
- Laboratoire d'Innovation Moléculaire et Applications (UMR CNRS 7042), Université de Strasbourg/Université de Haute-Alsace, ECPM, 67087, Strasbourg, France.
- Institut für Organische Chemie, Universität Würzburg, 97074 Würzburg, Germany.
| | - Lutz Ackermann
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, 37077, Göttingen, Germany.
- Wöhler Research Institute for Sustainable Chemistry (WISCh), Georg-August-Universität Göttingen, 37077, Göttingen, Germany.
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2
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Blackmond DG, Emmert M, Huryn DM, Neidig ML, Schaub T, Topczewski JJ, Bravo-Altamirano K, Buchan Z, Cabrera PJ. Academia or Industry: Lessons on Choosing Career Paths─There May Be More Than One Fork in the Road Ahead. Org Lett 2024; 26:2682-2685. [PMID: 38606472 DOI: 10.1021/acs.orglett.4c01099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Affiliation(s)
- Donna G Blackmond
- Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
| | - Marion Emmert
- Process Research & Development, MRL, Merck & Co., Inc., 126 E Lincoln Avenue, Rahway, New Jersey 07065, United States
| | - Donna M Huryn
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19194, United States
| | - Michael L Neidig
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Thomas Schaub
- Catalysis Research Laboratory (CaRLa), Im Neuenheimer Feld 584, 69120 Heidelberg, Germany
- BASF SE, Organic Synthesis, Carl-Bosch-Straße 38, 67056 Ludwigshafen, Germany
| | - Joseph J Topczewski
- Discovery Process Sciences, Small Molecule Discovery and Development, Corteva Agrisciences, 9330 Zionsville Road, Indianapolis, Indiana 46268, United States
| | - Karla Bravo-Altamirano
- Pfizer Worldwide Research and Development Medicine, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Zachary Buchan
- Discovery Chemistry, Small Molecule Discovery and Development, Corteva Agrisciences, 9330 Zionsville Road, Indianapolis, Indiana 46268, United States
| | - Pablo J Cabrera
- Chemical Research & Development, Pfizer Worldwide Research & Development, Eastern Point Road, Groton, Connecticut 06340, United States
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3
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Wowk V, Bauer AK, Radovic A, Chamoreau LM, Neidig ML, Lefèvre G. Divergent Fe-Mediated C-H Activation Paths Driven by Alkali Cations. JACS Au 2024; 4:512-524. [PMID: 38425937 PMCID: PMC10900209 DOI: 10.1021/jacsau.3c00649] [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] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/20/2023] [Accepted: 12/20/2023] [Indexed: 03/02/2024]
Abstract
The association of the ferrous complex FeIICl2(dmpe)2 (1) with alkali bases M(hmds) (M = Li, Na, K) proves to be an efficient platform for the activation of Ar-H bonds. Two mechanisms can be observed, leading to either Ar-FeII species by deprotonative ferration or hydrido species Ar-FeII-H by oxidative addition of transient Fe0(dmpe)2 generated by reduction of 1. Importantly, the nature of the alkali cation in M(hmds) has a strong influence on the preferred path. Starting from the same iron precursor, diverse catalytic applications can be explored by a simple modulation of the MI cation. Possible strategies enabling cross-coupling using arenes as pro-nucleophiles, reductive dehydrocoupling, or deuteration of B-H bonds are discussed.
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Affiliation(s)
- Vincent Wowk
- CNRS,
Institute of Chemistry for Life and Health Sciences, CSB2D, Chimie
ParisTech, PSL University, 75005 Paris, France
| | - Alexis K. Bauer
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Aleksa Radovic
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Lise-Marie Chamoreau
- CNRS,
Institut Parisien de Chimie Moléculaire, Sorbonne Université, F-75252 Paris, France
| | - Michael L. Neidig
- Inorganic
Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
| | - Guillaume Lefèvre
- CNRS,
Institute of Chemistry for Life and Health Sciences, CSB2D, Chimie
ParisTech, PSL University, 75005 Paris, France
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4
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Nam D, Bacik JP, Khade RL, Aguilera MC, Wei Y, Villada JD, Neidig ML, Zhang Y, Ando N, Fasan R. Mechanistic manifold in a hemoprotein-catalyzed cyclopropanation reaction with diazoketone. Nat Commun 2023; 14:7985. [PMID: 38042860 PMCID: PMC10693563 DOI: 10.1038/s41467-023-43559-7] [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] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 11/14/2023] [Indexed: 12/04/2023] Open
Abstract
Hemoproteins have recently emerged as promising biocatalysts for new-to-nature carbene transfer reactions. However, mechanistic understanding of the interplay between productive and unproductive pathways in these processes is limited. Using spectroscopic, structural, and computational methods, we investigate the mechanism of a myoglobin-catalyzed cyclopropanation reaction with diazoketones. These studies shed light on the nature and kinetics of key catalytic steps in this reaction, including the formation of an early heme-bound diazo complex intermediate, the rate-determining nature of carbene formation, and the cyclopropanation mechanism. Our analyses further reveal the existence of a complex mechanistic manifold for this reaction that includes a competing pathway resulting in the formation of an N-bound carbene adduct of the heme cofactor, which was isolated and characterized by X-ray crystallography, UV-Vis, and Mössbauer spectroscopy. This species can regenerate the active biocatalyst, constituting a non-productive, yet non-destructive detour from the main catalytic cycle. These findings offer a valuable framework for both mechanistic analysis and design of hemoprotein-catalyzed carbene transfer reactions.
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Affiliation(s)
- Donggeon Nam
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - John-Paul Bacik
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Rahul L Khade
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | | | - Yang Wei
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Juan D Villada
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, TX, 75080, USA
| | - Michael L Neidig
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK.
| | - Yong Zhang
- Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
| | - Nozomi Ando
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA.
| | - Rudi Fasan
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA.
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, TX, 75080, USA.
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5
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Gay BL, Wang YN, Bhatt S, Tarasewicz A, Cooke DJ, Milem EG, Zhang B, Gary JB, Neidig ML, Hull KL. Palladium and Iron Cocatalyzed Aerobic Alkene Aminoboration. J Am Chem Soc 2023; 145:18939-18947. [PMID: 37584107 PMCID: PMC10772865 DOI: 10.1021/jacs.3c05790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/17/2023]
Abstract
Aminoboration of simple alkenes with nitrogen nucleophiles remains an unsolved problem in synthetic chemistry; this transformation can be catalyzed by palladium via aminopalladation followed by transmetalation with a diboron reagent. However, this catalytic process faces inherent challenges with instability of the alkylpalladium(II) intermediate toward β-hydride elimination. Herein, we report a palladium/iron cocatalyzed aminoboration, which enables this transformation. We demonstrate these conditions on a variety of alkenes and norbornenes with an array of common nitrogen nucleophiles. In the developed strategy, the iron cocatalyst is crucial to achieving the desired reactivity by serving as a halophilic Lewis acid to release the transmetalation-active cationic alkylpalladium intermediate. Furthermore, it serves as a redox shuttle in the regeneration of the Pd(II) catalyst by reactivation of nanoparticulate palladium.
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Affiliation(s)
- Brittany L. Gay
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
| | - Ya-Nong Wang
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
| | - Shreeja Bhatt
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
| | - Anika Tarasewicz
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
| | - Daniel J. Cooke
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
| | - E. Grace Milem
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
- Stephen F. Austin State University, P.O. Box 13006, SFA Station, Nacogdoches, TX 75962, United States of America
| | - Bufan Zhang
- University of Rochester, 120 Trustee Road, Rochester, NY 14627, United States of America
| | - J. Brannon Gary
- Stephen F. Austin State University, P.O. Box 13006, SFA Station, Nacogdoches, TX 75962, United States of America
| | - Michael L. Neidig
- University of Rochester, 120 Trustee Road, Rochester, NY 14627, United States of America
- University of Oxford, S Parks Rd, Oxford OX1 3QR, United Kingdom
| | - Kami L. Hull
- University of Texas at Austin, 100 E. 24 Street, Austin, TX 78712 United States of America
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6
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Radović A, Wolford NJ, Li H, Brennessel WW, Xu H, Neidig ML. Mechanistic Studies of Iron-PyBOX-Catalyzed Olefin Amino-Oxygenation with Functionalized Hydroxylamines. Organometallics 2023; 42:1810-1817. [PMID: 37502313 PMCID: PMC10369677 DOI: 10.1021/acs.organomet.3c00067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Indexed: 07/29/2023]
Abstract
Iron-catalyzed amino-oxygenation of olefins often uses discrete ligands to increase reactivity and broaden substrate scope. This work is focused on examining ligand effects on reactivity and in situ iron speciation in a system which utilizes a bisoxazoline ligand. Freeze-trapped 57Fe Mössbauer and EPR spectroscopies as well as SC-XRD experiments were utilized to isolate and identify the species formed during the catalytic reaction of amino-oxygenation of olefins with functionalized hydroxylamines, as well as in the precatalytic mixture of iron salt and ligand. Experiments revealed significant influence of ligand and solvent on the speciation in the precatalytic mixture which led to the formation of different species which had significant influence on the reactivity. In situ experiments showed no evidence for the formation of an Fe(IV)-nitrene intermediate, and the isolation of a reactive intermediate was unsuccessful, suggesting that the use of the PyBOX ligand led to the formation of more reactive intermediates than observed in the previously studied system, preventing direct detection of intermediate species. However, isolation of the seven coordinate Fe(III) species with three carboxylate units of the hydroxylamine and spin-trap EPR experiments suggest formation of a species with unpaired electron density on the hydroxylamine nitrogen, which is in accordance with formation of a potential iron iminyl radical species, as recently proposed in literature. An observed increase in yield when substrates devoid of C-H bonds as well as isolation of a ring-closed dead-end species with substrates containing these bonds suggests the identity of the functionalized hydroxylamine can dictate the reactivity observed in these reactions.
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Affiliation(s)
- Aleksa Radović
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Nikki J. Wolford
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Hongze Li
- Department
of Chemistry, Brandeis University, Waltham, Massachusetts 02453, USA
| | | | - Hao Xu
- Department
of Chemistry, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Michael L. Neidig
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, USA
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7
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Aguilera M, Gogoi AR, Lee W, Liu L, Brennessel WW, Gutierrez O, Neidig ML. Insight into Radical Initiation, Solvent Effects, and Biphenyl Production in Iron-Bisphosphine Cross-Couplings. ACS Catal 2023; 13:8987-8996. [PMID: 37441237 PMCID: PMC10334425 DOI: 10.1021/acscatal.3c02008] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/31/2023] [Indexed: 07/15/2023]
Abstract
Iron-bisphosphines have attracted broad interest as highly effective and versatile catalytic systems for two- and three-component cross-coupling strategies. While recent mechanistic studies have defined the role of organoiron(II)-bisphosphine species as key intermediates for selective cross-coupled product formation in these systems, mechanistic features that are essential for catalytic performance remain undefined. Specifically, key questions include the following: what is the generality of iron(II) intermediates for radical initiation in cross-couplings? What factors control reactivity toward homocoupled biaryl side-products in these systems? Finally, what are the solvent effects in these reactions that enable high catalytic performance? Herein, we address these key questions by examining the mechanism of enantioselective coupling between α-chloro- and α-bromoalkanoates and aryl Grignard reagents catalyzed by chiral bisphosphine-iron complexes. By employing freeze-trapped 57Fe Mössbauer and EPR studies combined with inorganic synthesis, X-ray crystallography, reactivity studies, and quantum mechanical calculations, we define the key in situ iron speciation as well as their catalytic roles. In contrast to iron-SciOPP aryl-alkyl couplings, where monophenylated species were found to be the predominant reactive intermediate or prior proposals of reduced iron species to initiate catalysis, the enantioselective system utilizes an iron(II)-(R,R)-BenzP* bisphenylated intermediate to initiate the catalytic cycle. A profound consequence of this radical initiation process is that halogen abstraction and subsequent reductive elimination result in considerable amounts of biphenyl side products, limiting the efficiency of this method. Overall, this study offers key insights into the broader role of iron(II)-bisphosphine species for radical initiation, factors contributing to biphenyl side product generation, and protocol effects (solvent, Grignard reagent addition rate) that are critical to minimizing biphenyl generation to obtain more selective cross-coupling methods.
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Affiliation(s)
- Maria
Camila Aguilera
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Achyut Ranjan Gogoi
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Wes Lee
- Department
of Chemistry and Biochemistry, University
of Maryland, College Park, Maryland 20742, United States
| | - Lei Liu
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - William W. Brennessel
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Osvaldo Gutierrez
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843, United States
- Department
of Chemistry and Biochemistry, University
of Maryland, College Park, Maryland 20742, United States
| | - Michael L. Neidig
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, United States
- Inorganic
Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K.
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8
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Féo M, Bakas NJ, Radović A, Parisot W, Clisson A, Chamoreau LM, Haddad M, Ratovelomanana-Vidal V, Neidig ML, Lefèvre G. Thermally Stable Redox Noninnocent Bathocuproine-Iron Complex for Cycloaddition Reactions. ACS Catal 2023. [DOI: 10.1021/acscatal.3c00353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
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9
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Bakas NJ, Chourreu P, Gayon E, Lefèvre G, Neidig ML. The molecular-level effect of alkoxide additives in iron-catalyzed Kumada cross-coupling with simple ferric salts. Chem Commun (Camb) 2023; 59:1317-1320. [PMID: 36637039 PMCID: PMC10032548 DOI: 10.1039/d2cc06257g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The molecular-level role of alkoxide salts, used as alternative additive to N-methylpyrrolidone in iron-catalyzed alkyl-alkenyl/aryl cross-coupling reactions, is investigated. Detailed spectroscopic studies reveal that alkoxides promote the formation of homoleptic organoferrates such as [FeMe3]-, providing an alternative to toxic NMP to access these reactive intermediates.
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Affiliation(s)
- Nikki J Bakas
- Department of Chemistry, University of Rochester, Rochester, New York, 14627, USA.
| | - Pablo Chourreu
- CNRS, Institute of Chemistry for Life and Health sciences, CSB2D, Chimie ParisTech, PSL Research University, 75005, Paris, France.
- M2i Development, Bâtiment ChemStart'Up, Allée Le Corbusier, 64170, Lacq, France
| | - Eric Gayon
- M2i Development, Bâtiment ChemStart'Up, Allée Le Corbusier, 64170, Lacq, France
| | - Guillaume Lefèvre
- CNRS, Institute of Chemistry for Life and Health sciences, CSB2D, Chimie ParisTech, PSL Research University, 75005, Paris, France.
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York, 14627, USA.
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
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10
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Carpenter SH, Wolford NJ, Billow BS, Fetrow TV, Cajiao N, Radović A, Janicke MT, Neidig ML, Tondreau AM. Homoleptic Uranium-Bis(acyl)phosphide Complexes. Inorg Chem 2022; 61:12508-12517. [PMID: 35905438 DOI: 10.1021/acs.inorgchem.2c00639] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first uranium bis(acyl)phosphide (BAP) complexes were synthesized from the reaction between sodium bis(mesitoyl)phosphide (Na(mesBAP)) or sodium bis(2,4,6-triisopropylbenzoyl)phosphide (Na(trippBAP)) and UI3(1,4-dioxane)1.5. Thermally stable, homoleptic BAP complexes were characterized by single-crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy, when appropriate, for the elucidation of the electronic structure and bonding of these complexes. EPR spectroscopy revealed that the BAP ligands on the uranium center retain a significant amount of electron density. The EPR spectrum of the trivalent U(trippBAP)3 has a rhombic signal near g = 2 (g1 = 2.03; g2 = 2.01; and g3 = 1.98) that is consistent with the EPR-observed unpaired electron being located in a molecular orbital that appears ligand-derived. However, upon warming the complex to room temperature, no resonance was observed, indicating the presence of uranium character.
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Affiliation(s)
| | - Nikki J Wolford
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Brennan S Billow
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Taylor V Fetrow
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Nathalia Cajiao
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Aleksa Radović
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Michael T Janicke
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Aaron M Tondreau
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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11
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Agwara JN, Bakas NJ, Neidig ML, Porosoff MD. Challenges and Opportunities of Fe‐based Core‐Shell Catalysts for Fischer‐Tropsch Synthesis. ChemCatChem 2022. [DOI: 10.1002/cctc.202200289] [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: 11/09/2022]
Affiliation(s)
- Jane N. Agwara
- University of Rochester Department of Chemical Engineering UNITED STATES
| | - Nikki J. Bakas
- University of Rochester Department of Chemistry UNITED STATES
| | | | - Marc D. Porosoff
- University of Rochester Department of Chemical Engineering 4305 Wegmans HallBox 270166 14627 Rochester UNITED STATES
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12
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Wedal JC, Cajiao N, Neidig ML, Evans WJ. Anion-induced disproportionation of Th(III) complexes to form Th(II) and Th(IV) products. Chem Commun (Camb) 2022; 58:5289-5291. [PMID: 35403646 DOI: 10.1039/d2cc01272c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new synthesis of Th(II) complexes has been identified involving addition of simple MX salts (M = Li, Na, K; X = H, Cl, Me, N3) to Cp''3ThIII [Cp'' = [C5H3(SiMe3)2] in the presence of 18-crown-6 or 2.2.2-cryptand, forming [M(chelate)][Cp''3ThII] and Cp''3ThIVX. Cptet3ThIII (Cptet = C5Me4H) reacts with KH to form Cptet3ThIVH and the C-H bond activation product, [K(crypt)]{[Cptet2ThIVH[η1:η5-C5Me3H(CH2)]}.
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Affiliation(s)
- Justin C Wedal
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
| | - Nathalia Cajiao
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | - William J Evans
- Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
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13
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Bakas NJ, Sears JD, Brennessel WW, Neidig ML. A TMEDA-Iron Adduct Reaction Manifold in Iron-Catalyzed C(sp 2 )-C(sp 3 ) Cross-Coupling Reactions. Angew Chem Int Ed Engl 2022; 61:e202114986. [PMID: 35104376 PMCID: PMC8968675 DOI: 10.1002/anie.202114986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [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: 11/19/2021] [Indexed: 11/05/2022]
Abstract
Herein, we expand the current molecular-level understanding of one of the most important and effective additives in iron-catalyzed cross-coupling reactions, N,N,N',N'-tetramethylethylenediamine (TMEDA). Focusing on relevant phenyl and ethyl Grignard reagents and slow nucleophile addition protocols commonly used in effective catalytic systems, TMEDA-iron(II)-aryl intermediates are identified via in situ spectroscopy, X-ray crystallography, and detailed reaction studies to be a part of an iron(II)/(III)/(I) reaction cycle where radical recombination with FePhBr(TMEDA) (2Ph ) results in selective product formation in high yield. These results differ from prior studies with mesityl Grignard reagent, where poor product selectivity and low catalytic performance can be attributed to homoleptic iron-ate species. Overall, this study represents a critical advance in how amine additives such as TMEDA can modulate selectivity and reactivity of organoiron species in cross-coupling.
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Affiliation(s)
- Nikki J Bakas
- Department of Chemistry, B31 Hutchison Hall, University of Rochester, 120 Trustee Rd, Rochester, NY 14627, USA
| | - Jeffrey D Sears
- Department of Chemistry, B31 Hutchison Hall, University of Rochester, 120 Trustee Rd, Rochester, NY 14627, USA
| | - William W Brennessel
- Department of Chemistry, B31 Hutchison Hall, University of Rochester, 120 Trustee Rd, Rochester, NY 14627, USA
| | - Michael L Neidig
- Department of Chemistry, B31 Hutchison Hall, University of Rochester, 120 Trustee Rd, Rochester, NY 14627, USA
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14
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Wang S, Sears JD, Moore CE, Rheingold AL, Neidig ML, Figueroa JS. Side-on coordination of diphosphorus to a mononuclear iron center. Science 2022; 375:1393-1397. [PMID: 35324298 PMCID: PMC9210196 DOI: 10.1126/science.abn7100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The diagonal relationship in the periodic table between phosphorus and carbon has set an expectation that the triple-bonded diatomic diphosphorus molecule (P2) should more closely mimic the attributes of acetylene (HC≡CH) rather than its group 15 congener dinitrogen (N2). Although acetylene has well-documented coordination chemistry with mononuclear transition metals, coordination complexes that feature P2 bound to a single metal center have remained elusive. We report the isolation and x-ray crystallographic characterization of a mononuclear iron complex featuring P2 coordination in a side-on, η2-binding mode. An analogous η2-bound bis-timethylsilylacetylene iron complex is reported for comparison. Nuclear magnetic resonance, infrared, and Mössbauer spectroscopic analysis-in conjunction with density functional theory calculations-demonstrate that η2-P2 and η2-acetylene ligands exert a similar electronic demand on mononuclear iron centers but exhibit different reactivity profiles.
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Affiliation(s)
- Shuai Wang
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA, 92093-0358, USA
| | - Jeffrey D. Sears
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | - Curtis E. Moore
- Department of Chemistry, The Ohio State University, 88 West 18th Avenue, Columbus, OH 43210, USA
| | - Arnold L. Rheingold
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA, 92093-0358, USA
| | - Michael L. Neidig
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | - Joshua S. Figueroa
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA, 92093-0358, USA
- Corresponding author.
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15
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Bakas NJ, Sears JD, Brennessel WW, Neidig ML. A TMEDA–Iron Adduct Reaction Manifold in Iron‐Catalyzed C(sp
2
)−C(sp
3
) Cross‐Coupling Reactions. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202114986] [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: 11/08/2022]
Affiliation(s)
- Nikki J. Bakas
- Department of Chemistry B31 Hutchison Hall University of Rochester 120 Trustee Rd Rochester NY 14627 USA
| | - Jeffrey D. Sears
- Department of Chemistry B31 Hutchison Hall University of Rochester 120 Trustee Rd Rochester NY 14627 USA
| | - William W. Brennessel
- Department of Chemistry B31 Hutchison Hall University of Rochester 120 Trustee Rd Rochester NY 14627 USA
| | - Michael L. Neidig
- Department of Chemistry B31 Hutchison Hall University of Rochester 120 Trustee Rd Rochester NY 14627 USA
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16
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Gaiser AN, Celis-Barros C, White FD, Beltran-Leiva MJ, Sperling JM, Salpage SR, Poe TN, Gomez Martinez D, Jian T, Wolford NJ, Jones NJ, Ritz AJ, Lazenby RA, Gibson JK, Baumbach RE, Páez-Hernández D, Neidig ML, Albrecht-Schönzart TE. Creation of an unexpected plane of enhanced covalency in cerium(III) and berkelium(III) terpyridyl complexes. Nat Commun 2021; 12:7230. [PMID: 34893651 PMCID: PMC8664847 DOI: 10.1038/s41467-021-27576-y] [Citation(s) in RCA: 3] [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: 02/05/2021] [Accepted: 11/30/2021] [Indexed: 11/28/2022] Open
Abstract
Controlling the properties of heavy element complexes, such as those containing berkelium, is challenging because relativistic effects, spin-orbit and ligand-field splitting, and complex metal-ligand bonding, all dictate the final electronic states of the molecules. While the first two of these are currently beyond experimental control, covalent M‒L interactions could theoretically be boosted through the employment of chelators with large polarizabilities that substantially shift the electron density in the molecules. This theory is tested by ligating BkIII with 4'-(4-nitrophenyl)-2,2':6',2"-terpyridine (terpy*), a ligand with a large dipole. The resultant complex, Bk(terpy*)(NO3)3(H2O)·THF, is benchmarked with its closest electrochemical analog, Ce(terpy*)(NO3)3(H2O)·THF. Here, we show that enhanced Bk‒N interactions with terpy* are observed as predicted. Unexpectedly, induced polarization by terpy* also creates a plane in the molecules wherein the M‒L bonds trans to terpy* are shorter than anticipated. Moreover, these molecules are highly anisotropic and rhombic EPR spectra for the CeIII complex are reported.
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Affiliation(s)
- Alyssa N Gaiser
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Cristian Celis-Barros
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Frankie D White
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Maria J Beltran-Leiva
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Joseph M Sperling
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Sahan R Salpage
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Todd N Poe
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Daniela Gomez Martinez
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Tian Jian
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Nikki J Wolford
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - Nathaniel J Jones
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Amanda J Ritz
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - Robert A Lazenby
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, 32306, USA
| | - John K Gibson
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Ryan E Baumbach
- National High Magnetic Field Laboratory, Tallahassee, FL, 32310, USA
| | - Dayán Páez-Hernández
- Center for Applied Nanosciences, Universidad Andres Bello, República 275, Santiago, Chile
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
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17
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Abstract
A mechanistic study is performed on the reaction method for iron-catalyzed C-H methylation with AlMe3 reagent, previously proposed to involve cyclometalated iron(III) intermediates and an iron(III)/(I) reaction cycle. Detailed spectroscopic studies (57Fe Mössbauer, EPR) during catalysis and in stoichiometric reactions identify iron(II) complexes, including cyclometalated iron(II) intermediates, as the major iron species formed in situ under catalytic reaction conditions. Reaction studies identify a cyclometalated iron(II)-methyl species as the key intermediate leading to C-H methylated product upon reaction with oxidant, consistent with a previously proposed iron(II)/iron(III)/iron(I) reaction manifold for C-H arylation.
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Affiliation(s)
- Shilpa Bhatia
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | - Joshua C DeMuth
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
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18
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Wong AS, Zhang B, Li B, Neidig ML, Byers JA. Air-Stable Iron-Based Precatalysts for Suzuki–Miyaura Cross-Coupling Reactions between Alkyl Halides and Aryl Boronic Esters. Org Process Res Dev 2021; 25:2461-2472. [DOI: 10.1021/acs.oprd.1c00235] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Alexander S. Wong
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Bufan Zhang
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Bo Li
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
| | - Michael L. Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Jeffery A. Byers
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, United States
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19
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Liu L, Aguilera MC, Lee W, Youshaw CR, Neidig ML, Gutierrez O. General method for iron-catalyzed multicomponent radical cascades-cross-couplings. Science 2021; 374:432-439. [PMID: 34672739 DOI: 10.1126/science.abj6005] [Citation(s) in RCA: 12] [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: 01/03/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- Lei Liu
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | | | - Wes Lee
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Cassandra R Youshaw
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | - Osvaldo Gutierrez
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.,Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
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20
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Wolford NJ, Muñoz SB, Neate PGN, Brennessel WW, Neidig ML. NHC Effects on Reduction Dynamics in Iron-Catalyzed Organic Transformations*. Chemistry 2021; 27:13651-13658. [PMID: 34214195 PMCID: PMC8463511 DOI: 10.1002/chem.202102070] [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: 06/11/2021] [Indexed: 11/07/2022]
Abstract
The high abundance, low toxicity and rich redox chemistry of iron has resulted in a surge of iron-catalyzed organic transformations over the last two decades. Within this area, N-heterocyclic carbene (NHC) ligands have been widely utilized to achieve high yields across reactions including cross-coupling and C-H alkylation, amongst others. Central to the development of iron-NHC catalytic methods is the understanding of iron speciation and the propensity of these species to undergo reduction events, as low-valent iron species can be advantageous or undesirable from one system to the next. This study highlights the importance of the identity of the NHC on iron speciation upon reaction with EtMgBr, where reactions with SIMes and IMes NHCs were shown to undergo β-hydride elimination more readily than those with SIPr and IPr NHCs. This insight is vital to developing new iron-NHC catalyzed transformations as understanding how to control this reduction by simply changing the NHC is central to improving the reactivity in iron-NHC catalysis.
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Affiliation(s)
- Nikki J Wolford
- Department of Chemistry, University of Rochester, 120 Trustee Rd, Rochester, NY, 14627, USA
| | - Salvador B Muñoz
- Department of Chemistry, University of Rochester, 120 Trustee Rd, Rochester, NY, 14627, USA
| | - Peter G N Neate
- Department of Chemistry, University of Rochester, 120 Trustee Rd, Rochester, NY, 14627, USA
| | - William W Brennessel
- Department of Chemistry, University of Rochester, 120 Trustee Rd, Rochester, NY, 14627, USA
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, 120 Trustee Rd, Rochester, NY, 14627, USA
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21
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Neate PGN, Zhang B, Conforti J, Brennessel WW, Neidig ML. Dilithium Amides as a Modular Bis-Anionic Ligand Platform for Iron-Catalyzed Cross-Coupling. Org Lett 2021; 23:5958-5963. [PMID: 34310141 DOI: 10.1021/acs.orglett.1c02053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Dilithium amides have been developed as a bespoke and general ligand for iron-catalyzed Kumada-Tamao-Corriu cross-coupling reactions, their design taking inspiration from previous mechanistic and structural studies. They allow for the cross-coupling of alkyl Grignard reagents with sp2-hybridized electrophiles as well as aryl Grignard reagents with sp3-hybridized electrophiles. This represents a rare example of a single iron-catalyzed system effective across diverse coupling reactions without significant modification of the catalytic protocol, as well as remaining operationally simple.
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Affiliation(s)
- Peter G N Neate
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Bufan Zhang
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Jessica Conforti
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - William W Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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22
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Abstract
The use of iron catalysts in carbon-carbon bond forming reactions is of interest as an alternative to precious metal catalysts, offering reduced cost, lower toxicity, and different reactivity. While well-defined ligands such as N-heterocyclic carbenes (NHCs) and phosphines can be highly effective in these reactions, additional additives such as N-methylpyrrolidone (NMP), N,N,N',N'-tetramethylethylenediamine (TMEDA), and iron salts that alter speciation can also be employed to achieve high product yields. However, in contrast to well-defined iron ligands, the roles of these additives are often ambiguous, and molecular-level insights into how they achieve effective catalysis are not well-defined. Using a unique physical-inorganic in situ spectroscopic approach, detailed insights into the effect of additives on iron speciation, mechanism, and catalysis can inform further reaction development. In this Perspective, recent advances will be discussed as well as ongoing challenges and potential opportunities in iron-catalyzed reactions.
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Affiliation(s)
- Nikki J Bakas
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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23
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DeMuth JC, Song Z, Carpenter SH, Boddie TE, Radović A, Baker TM, Gutierrez O, Neidig ML. Experimental and computational studies of the mechanism of iron-catalysed C-H activation/functionalisation with allyl electrophiles. Chem Sci 2021; 12:9398-9407. [PMID: 34349913 PMCID: PMC8278975 DOI: 10.1039/d1sc01661j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/23/2021] [Indexed: 11/21/2022] Open
Abstract
Synthetic methods that utilise iron to facilitate C–H bond activation to yield new C–C and C–heteroatom bonds continue to attract significant interest. However, the development of these systems is still hampered by a limited molecular-level understanding of the key iron intermediates and reaction pathways that enable selective product formation. While recent studies have established the mechanism for iron-catalysed C–H arylation from aryl-nucleophiles, the underlying mechanistic pathway of iron-catalysed C–H activation/functionalisation systems which utilise electrophiles to establish C–C and C–heteroatom bonds has not been determined. The present study focuses on an iron-catalysed C–H allylation system, which utilises allyl chlorides as electrophiles to establish a C–allyl bond. Freeze-trapped inorganic spectroscopic methods (57Fe Mössbauer, EPR, and MCD) are combined with correlated reaction studies and kinetic analyses to reveal a unique and rapid reaction pathway by which the allyl electrophile reacts with a C–H activated iron intermediate. Supporting computational analysis defines this novel reaction coordinate as an inner-sphere radical process which features a partial iron–bisphosphine dissociation. Highlighting the role of the bisphosphine in this reaction pathway, a complementary study performed on the reaction of allyl electrophile with an analogous C–H activated intermediate bearing a more rigid bisphosphine ligand exhibits stifled yield and selectivity towards allylated product. An additional spectroscopic analysis of an iron-catalysed C–H amination system, which incorporates N-chloromorpholine as the C–N bond-forming electrophile, reveals a rapid reaction of electrophile with an analogous C–H activated iron intermediate consistent with the inner-sphere radical process defined for the C–H allylation system, demonstrating the prevalence of this novel reaction coordinate in this sub-class of iron-catalysed C–H functionalisation systems. Overall, these results provide a critical mechanistic foundation for the rational design and development of improved systems that are efficient, selective, and useful across a broad range of C–H functionalisations. Experimental and computational studies support an inner-sphere radical pathway for iron-catalysed C–H activation/functionalisation with allyl electrophiles.![]()
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Affiliation(s)
- Joshua C DeMuth
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Zhihui Song
- Department of Chemistry and Biochemistry, University of Maryland College Park Maryland 20742 USA
| | | | - Theresa E Boddie
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Aleksa Radović
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Tessa M Baker
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Osvaldo Gutierrez
- Department of Chemistry and Biochemistry, University of Maryland College Park Maryland 20742 USA
| | - Michael L Neidig
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
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24
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Liang Q, DeMuth JC, Radović A, Wolford NJ, Neidig ML, Song D. [2Fe-2S] Cluster Supported by Redox-Active o-Phenylenediamide Ligands and Its Application toward Dinitrogen Reduction. Inorg Chem 2021; 60:13811-13820. [PMID: 34043353 DOI: 10.1021/acs.inorgchem.1c00683] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
As prevalent cofactors in living organisms, iron-sulfur clusters participate in not only the electron-transfer processes but also the biosynthesis of other cofactors. Many synthetic iron-sulfur clusters have been used in model studies, aiming to mimic their biological functions and to gain mechanistic insight into the related biological systems. The smallest [2Fe-2S] clusters are typically used for one-electron processes because of their limited capacity. Our group is interested in functionalizing small iron-sulfur clusters with redox-active ligands to enhance their electron storage capacity, because such functionalized clusters can potentially mediate multielectron chemical transformations. Herein we report the synthesis, structural characterization, and catalytic activity of a diferric [2Fe-2S] cluster functionalized with two o-phenylenediamide ligands. The electrochemical and chemical reductions of such a cluster revealed rich redox chemistry. The functionalized diferric cluster can store up to four electrons reversibly, where the first two reduction events are ligand-based and the remainder metal-based. The diferric [2Fe-2S] cluster displays catalytic activity toward silylation of dinitrogen, affording up to 88 equiv of the amine product per iron center.
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Affiliation(s)
- Qiuming Liang
- Davenport Chemical Research Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Joshua C DeMuth
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Aleksa Radović
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Nikki J Wolford
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Datong Song
- Davenport Chemical Research Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada
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25
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Curran DJ, Ganguly G, Heit YN, Wolford NJ, Minasian SG, Löble MW, Cary SK, Kozimor SA, Autschbach J, Neidig ML. Near-infrared C-term MCD spectroscopy of octahedral uranium(V) complexes. Dalton Trans 2021; 50:5483-5492. [PMID: 33908963 DOI: 10.1039/d1dt00513h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
C-term magnetic circular dichroism (MCD) spectroscopy is a powerful method for probing d-d and f-f transitions in paramagnetic metal complexes. However, this technique remains underdeveloped both experimentally and theoretically for studies of U(v) complexes of Oh symmetry, which have been of longstanding interest for probing electronic structure, bonding, and covalency in 5f systems. In this study, C-term NIR MCD of the Laporte forbidden f-f transitions of [UCl6]- and [UF6]- are reported, demonstrating the significant fine structure resolution possible with this technique including for the low energy Γ7 → Γ8 transitions in [UF6]-. The experimental NIR MCD studies were further extended to [U(OC6F5)6]-, [U(CH2SiMe3)6]-, and [U(NC(tBu)(Ph))6]- to evaluate the effects of ligand-type on the f-f MCD fine structure features. Theoretical calculations were conducted to determine the Laporte forbidden f-f transitions and their MCD intensity experimentally observed in the NIR spectra of the U(v) hexahalide complexes, via the inclusion of vibronic coupling, to better understand the underlying spectral fine structure features for these complexes. These spectra and simulations provide an important platform for the application of MCD spectroscopy to this widely studied class of U(v) complexes and identify areas for continued theoretical development.
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Affiliation(s)
- Daniel J Curran
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | - Gaurab Ganguly
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
| | - Yonaton N Heit
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
| | - Nikki J Wolford
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
| | - Stefan G Minasian
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Matthias W Löble
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
| | - Samantha K Cary
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
| | - Stosh A Kozimor
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
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26
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27
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Wolford NJ, Radovic A, Neidig ML. C-Term magnetic circular dichroism (MCD) spectroscopy in paramagnetic transition metal and f-element organometallic chemistry. Dalton Trans 2021; 50:416-428. [PMID: 33315022 DOI: 10.1039/d0dt03730c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Magnetic circular dichroism (MCD) spectroscopy is a powerful experiment used to probe the electronic structure and bonding in paramagnetic metal-based complexes. While C-term MCD spectroscopy has been utilized in many areas of chemistry, it has been underutilized in studying paramagnetic organometallic transition metal and f-element complexes. From the analysis of isolated organometallic complexes to the study of in situ generated species, MCD can provide information regarding ligand interactions, oxidation and spin state, and geometry and coordination environment of paramagnetic species. The pratical aspects of this technique, such as air-free sample preparation and cryogenic experimental temperatures, allow for the study of highly unstable species, something that is often difficult with other spectroscopic techniques. This perspective highlights MCD studies of both transition metal and f-element organometallic complexes, including in situ generated reactive intermediates, to demonstrate the utility of this technique in probing electronic structure, bonding and mechanism in paramagnetic organometallic chemistry.
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Affiliation(s)
- Nikki J Wolford
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
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28
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Nurdin L, Yang Y, Neate PGN, Piers WE, Maron L, Neidig ML, Lin JB, Gelfand BS. Activation of ammonia and hydrazine by electron rich Fe(ii) complexes supported by a dianionic pentadentate ligand platform through a common terminal Fe(iii) amido intermediate. Chem Sci 2020; 12:2231-2241. [PMID: 34163989 PMCID: PMC8179247 DOI: 10.1039/d0sc06466a] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We report the use of electron rich iron complexes supported by a dianionic diborate pentadentate ligand system, B2Pz4Py, for the coordination and activation of ammonia (NH3) and hydrazine (NH2NH2). For ammonia, coordination to neutral (B2Pz4Py)Fe(ii) or cationic [(B2Pz4Py)Fe(iii)]+ platforms leads to well characterized ammine complexes from which hydrogen atoms or protons can be removed to generate, fleetingly, a proposed (B2Pz4Py)Fe(iii)–NH2 complex (3Ar-NH2). DFT computations suggest a high degree of spin density on the amido ligand, giving it significant aminyl radical character. It rapidly traps the H atom abstracting agent 2,4,6-tri-tert-butylphenoxy radical (ArO˙) to form a C–N bond in a fully characterized product (2Ar), or scavenges hydrogen atoms to return to the ammonia complex (B2Pz4Py)Fe(ii)–NH3 (1Ar-NH3). Interestingly, when (B2Pz4Py)Fe(ii) is reacted with NH2NH2, a hydrazine bridged dimer, (B2Pz4Py)Fe(ii)–NH2NH2–Fe(ii)(B2Pz4Py) ((1Ar)2-NH2NH2), is observed at −78 °C and converts to a fully characterized bridging diazene complex, 4Ar, along with ammonia adduct 1Ar-NH3 as it is allowed to warm to room temperature. Experimental and computational evidence is presented to suggest that (B2Pz4Py)Fe(ii) induces reductive cleavage of the N–N bond in hydrazine to produce the Fe(iii)–NH2 complex 3Ar-NH2, which abstracts H˙ atoms from (1Ar)2-NH2NH2 to generate the observed products. All of these transformations are relevant to proposed steps in the ammonia oxidation reaction, an important process for the use of nitrogen-based fuels enabled by abundant first row transition metals. Synopsis: a highly reactive Fe(iii)–NH2 complex is generated via activation of ammonia or hydrazine in reactions of relevance to fundamental steps in ammonia oxidation processes mediated by an abundant, first row transition metal.![]()
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Affiliation(s)
- Lucie Nurdin
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Yan Yang
- LPCNO, Université de Toulouse, INSA, UPS Toulouse France
| | - Peter G N Neate
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Warren E Piers
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Laurent Maron
- LPCNO, Université de Toulouse, INSA, UPS Toulouse France
| | - Michael L Neidig
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Jian-Bin Lin
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Benjamin S Gelfand
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
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29
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Neate PGN, Greenhalgh MD, Brennessel WW, Thomas SP, Neidig ML. TMEDA in Iron-Catalyzed Hydromagnesiation: Formation of Iron(II)-Alkyl Species for Controlled Reduction to Alkene-Stabilized Iron(0). Angew Chem Int Ed Engl 2020; 59:17070-17076. [PMID: 32542848 DOI: 10.1002/anie.202006639] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [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: 05/07/2020] [Indexed: 12/16/2022]
Abstract
N,N,N',N'-Tetramethylethylenediamine (TMEDA) has been one of the most prevalent and successful additives used in iron catalysis, finding application in reactions as diverse as cross-coupling, C-H activation, and borylation. However, the role that TMEDA plays in these reactions remains largely undefined. Herein, studying the iron-catalyzed hydromagnesiation of styrene derivatives using TMEDA has provided molecular-level insight into the role of TMEDA in achieving effective catalysis. The key is the initial formation of TMEDA-iron(II)-alkyl species which undergo a controlled reduction to selectively form catalytically active styrene-stabilized iron(0)-alkyl complexes. While TMEDA is not bound to the catalytically active species, these active iron(0) complexes cannot be accessed in the absence of TMEDA. This mode of action, allowing for controlled reduction and access to iron(0) species, represents a new paradigm for the role of this important reaction additive in iron catalysis.
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Affiliation(s)
- Peter G N Neate
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Mark D Greenhalgh
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - William W Brennessel
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Stephen P Thomas
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
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30
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Sears JD, Sergentu D, Baker TM, Brennessel WW, Autschbach J, Neidig ML. The Exceptional Diversity of Homoleptic Uranium–Methyl Complexes. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202005138] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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)
- Jeffrey D. Sears
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | | | - Tessa M. Baker
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - William W. Brennessel
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Jochen Autschbach
- Department of Chemistry University at Buffalo State University of New York Buffalo NY 14260 USA
| | - Michael L. Neidig
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
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31
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Neate PGN, Greenhalgh MD, Brennessel WW, Thomas SP, Neidig ML. TMEDA in Iron‐Catalyzed Hydromagnesiation: Formation of Iron(II)‐Alkyl Species for Controlled Reduction to Alkene‐Stabilized Iron(0). Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006639] [Citation(s) in RCA: 4] [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: 12/11/2022]
Affiliation(s)
- Peter G. N. Neate
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | | | - William W. Brennessel
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Stephen P. Thomas
- EaStCHEM School of Chemistry University of Edinburgh Joseph Black Building David Brewster Road Edinburgh EH9 3FJ UK
| | - Michael L. Neidig
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
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32
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Sears JD, Sergentu DC, Baker TM, Brennessel WW, Autschbach J, Neidig ML. The Exceptional Diversity of Homoleptic Uranium-Methyl Complexes. Angew Chem Int Ed Engl 2020; 59:13586-13590. [PMID: 32392392 DOI: 10.1002/anie.202005138] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [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: 04/09/2020] [Revised: 05/07/2020] [Indexed: 11/11/2022]
Abstract
Homoleptic σ-bonded uranium-alkyl complexes have been a synthetic target since the Manhattan Project. The current study describes the synthesis and characterization of several unprecedented uranium-methyl complexes. Amongst these complexes, the first example of a homoleptic uranium-alkyl dimer, [Li(THF)4 ]2 [U2 (CH3 )10 ], as well as a seven-coordinate uranium-methyl monomer, {Li(OEt2 )Li(OEt2 )2 UMe7 Li}n were both crystallographically identified. The diversity of complexes reported herein provides critical insight into the structural diversity, electronic structure and bonding in uranium-alkyl chemistry.
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Affiliation(s)
- Jeffrey D Sears
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Dumitru-Claudiu Sergentu
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Tessa M Baker
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - William W Brennessel
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY, 14260, USA
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
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33
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Wolford NJ, Yu X, Bart SC, Autschbach J, Neidig ML. Ligand effects on electronic structure and bonding in U(iii) coordination complexes: a combined MCD, EPR and computational study. Dalton Trans 2020; 49:14401-14410. [DOI: 10.1039/d0dt02929g] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spectroscopy and theory enable broader insight into electronic structure and bonding in U(iii) coordination complexes, focusing on systems with Tp* ligands.
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Affiliation(s)
| | - Xiaojuan Yu
- Department of Chemistry
- University at Buffalo
- State University of New York
- Buffalo
- USA
| | - Suzanne C. Bart
- H.C. Brown Laboratory
- Department of Chemistry
- Purdue University
- West Lafayette
- USA
| | - Jochen Autschbach
- Department of Chemistry
- University at Buffalo
- State University of New York
- Buffalo
- USA
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34
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Liang Q, Lin JH, DeMuth JC, Neidig ML, Song D. Syntheses and characterizations of iron complexes of bulky o-phenylenediamide ligand. Dalton Trans 2020; 49:12287-12297. [DOI: 10.1039/d0dt02087g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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
We report the reactivity of the iron complexes of a bulky phenylenediamide ligand.
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Affiliation(s)
- Qiuming Liang
- Davenport Chemical Research Laboratories
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | - Jack H. Lin
- Davenport Chemical Research Laboratories
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
| | | | | | - Datong Song
- Davenport Chemical Research Laboratories
- Department of Chemistry
- University of Toronto
- Toronto
- Canada
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35
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Affiliation(s)
- Stephanie H. Carpenter
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - William W. Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Michael L. Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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36
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Fleischauer VE, Ganguly G, Woen DH, Wolford NJ, Evans WJ, Autschbach J, Neidig ML. Insight into the Electronic Structure of Formal Lanthanide(II) Complexes using Magnetic Circular Dichroism Spectroscopy. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00315] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [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)
- Valerie E. Fleischauer
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Gaurab Ganguly
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14206-3000, United States
| | - David H. Woen
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Nikki J. Wolford
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - William J. Evans
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14206-3000, United States
| | - Michael L. Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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37
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Cabrera-Lobera N, Quirós MT, Brennessel WW, Neidig ML, Buñuel E, Cárdenas DJ. Atom-Economical Ni-Catalyzed Diborylative Cyclization of Enynes: Preparation of Unsymmetrical Diboronates. Org Lett 2019; 21:6552-6556. [PMID: 31356084 DOI: 10.1021/acs.orglett.9b02485] [Citation(s) in RCA: 13] [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: 01/12/2023]
Abstract
We report a Ni-catalyzed diborylative cyclization of enynes that affords carbo- and heterocycles containing both alkyl- and alkenylboronates. The reaction is fully atom-economical, shows a broad scope, and employs a powerful and inexpensive catalytic Ni-based system. The reaction mechanism seems to involve activation of the enyne by Ni(0) through oxidative cyclometalation of the enyne prior to diboron reagent activation. An unprecedented dinuclear bis(organometallic) Ni(I) intermediate complex was isolated.
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Affiliation(s)
- Natalia Cabrera-Lobera
- Departamento de Química Orgánica , Facultad de Ciencias, Universidad Autónoma de Madrid, Institute for Advanced Research in Chemical Sciences (IAdChem) , Av. Francisco Tomás y Valiente 7, Cantoblanco 28049 , Madrid , Spain
| | - M Teresa Quirós
- Departamento de Química Orgánica , Facultad de Ciencias, Universidad Autónoma de Madrid, Institute for Advanced Research in Chemical Sciences (IAdChem) , Av. Francisco Tomás y Valiente 7, Cantoblanco 28049 , Madrid , Spain
| | - William W Brennessel
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Michael L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Elena Buñuel
- Departamento de Química Orgánica , Facultad de Ciencias, Universidad Autónoma de Madrid, Institute for Advanced Research in Chemical Sciences (IAdChem) , Av. Francisco Tomás y Valiente 7, Cantoblanco 28049 , Madrid , Spain
| | - Diego J Cárdenas
- Departamento de Química Orgánica , Facultad de Ciencias, Universidad Autónoma de Madrid, Institute for Advanced Research in Chemical Sciences (IAdChem) , Av. Francisco Tomás y Valiente 7, Cantoblanco 28049 , Madrid , Spain
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38
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Boddie TE, Carpenter SH, Baker TM, DeMuth JC, Cera G, Brennessel WW, Ackermann L, Neidig ML. Identification and Reactivity of Cyclometalated Iron(II) Intermediates in Triazole-Directed Iron-Catalyzed C–H Activation. J Am Chem Soc 2019; 141:12338-12345. [DOI: 10.1021/jacs.9b05269] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Theresa E. Boddie
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Stephanie H. Carpenter
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Tessa M. Baker
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Joshua C. DeMuth
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Gianpiero Cera
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077, Gottingen, Germany
| | - William W. Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Lutz Ackermann
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37077, Gottingen, Germany
| | - Michael L. Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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39
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Wolford NJ, Sergentu D, Brennessel WW, Autschbach J, Neidig ML. Homoleptic Aryl Complexes of Uranium (IV). Angew Chem Int Ed Engl 2019; 58:10266-10270. [DOI: 10.1002/anie.201905423] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Indexed: 11/09/2022]
Affiliation(s)
- Nikki J. Wolford
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Dumitru‐Claudiu Sergentu
- Department of Chemistry University at Buffalo State University of New York 312 Natural Sciences Complex Buffalo NY 14260 USA
| | - William W. Brennessel
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Jochen Autschbach
- Department of Chemistry University at Buffalo State University of New York 312 Natural Sciences Complex Buffalo NY 14260 USA
| | - Michael L. Neidig
- Department of Chemistry University of Rochester, B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
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40
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Neate PGN, Greenhalgh MD, Brennessel WW, Thomas SP, Neidig ML. Mechanism of the Bis(imino)pyridine-Iron-Catalyzed Hydromagnesiation of Styrene Derivatives. J Am Chem Soc 2019; 141:10099-10108. [PMID: 31150210 DOI: 10.1021/jacs.9b04869] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron-catalyzed hydromagnesiation of styrene derivatives offers a rapid and efficient method to generate benzylic Grignard reagents, which can be applied in a range of transformations to provide products of formal hydrofunctionalization. While iron-catalyzed methodologies exist for the hydromagnesiation of terminal alkenes, internal alkynes, and styrene derivatives, the underlying mechanisms of catalysis remain largely undefined. To address this issue and determine the divergent reactivity from established cross-coupling and hydrofunctionalization reactions, a detailed study of the bis(imino)pyridine iron-catalyzed hydromagnesiation of styrene derivatives is reported. Using a combination of kinetic analysis, deuterium labeling, and reactivity studies as well as in situ 57Fe Mössbauer spectroscopy, key mechanistic features and species were established. A formally iron(0) ate complex [ iPrBIPFe(Et)(CH2═CH2)]- was identified as the principle resting state of the catalyst. Dissociation of ethene forms the catalytically active species which can reversibly coordinate the styrene derivative and mediate a direct and reversible β-hydride transfer, negating the necessity of a discrete iron hydride intermediate. Finally, displacement of the tridentate bis(imino)pyridine ligand over the course of the reaction results in the formation of a tris-styrene-coordinated iron(0) complex, which is also a competent catalyst for hydromagnesiation.
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Affiliation(s)
- Peter G N Neate
- EaStCHEM School of Chemistry , University of Edinburgh , David Brewster Road , Edinburgh EH9 3FJ , U.K.,Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Mark D Greenhalgh
- EaStCHEM School of Chemistry , University of Edinburgh , David Brewster Road , Edinburgh EH9 3FJ , U.K
| | - William W Brennessel
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Stephen P Thomas
- EaStCHEM School of Chemistry , University of Edinburgh , David Brewster Road , Edinburgh EH9 3FJ , U.K
| | - Michael L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
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41
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Drance MJ, Sears JD, Mrse AM, Moore CE, Rheingold AL, Neidig ML, Figueroa JS. Terminal coordination of diatomic boron monofluoride to iron. Science 2019; 363:1203-1205. [PMID: 30872521 DOI: 10.1126/science.aaw6102] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 02/19/2019] [Indexed: 11/02/2022]
Abstract
Boron monofluoride (BF) is a diatomic molecule with 10 valence electrons, isoelectronic to carbon monoxide (CO). Unlike CO, which is a stable molecule at room temperature and readily serves as both a bridging and terminal ligand to transition metals, BF is unstable below 1800°C in the gas phase, and its coordination chemistry is substantially limited. Here, we report the isolation of the iron complex Fe(BF)(CO)2(CNArTripp2)2 [ArTripp2, 2,6-(2,4,6-(i-Pr)3C6H2]2C6H3; i-Pr, iso-propyl], featuring a terminal BF ligand. Single-crystal x-ray diffraction as well as nuclear magnetic resonance, infrared, and Mössbauer spectroscopic studies on Fe(BF)(CO)2(CNArTripp2)2 and the isoelectronic dinitrogen (N2) and CO complexes Fe(N2)(CO)2(CNArTripp2)2 and Fe(CO)3(CNArTripp2)2 demonstrate that the terminal BF ligand possesses particularly strong σ-donor and π-acceptor properties. Density functional theory and electron-density topology calculations support this conclusion.
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Affiliation(s)
- Myles J Drance
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA 92093-0358, USA
| | - Jeffrey D Sears
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | - Anthony M Mrse
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA 92093-0358, USA
| | - Curtis E Moore
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA 92093-0358, USA
| | - Arnold L Rheingold
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA 92093-0358, USA
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | - Joshua S Figueroa
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, CA 92093-0358, USA.
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42
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Sears JD, Muñoz SB, Daifuku SL, Shaps AA, Carpenter SH, Brennessel WW, Neidig ML. The Effect of β-Hydrogen Atoms on Iron Speciation in Cross-Couplings with Simple Iron Salts and Alkyl Grignard Reagents. Angew Chem Int Ed Engl 2019; 58:2769-2773. [PMID: 30653812 PMCID: PMC6472485 DOI: 10.1002/anie.201813578] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 01/07/2019] [Indexed: 11/08/2022]
Abstract
The effects of β-hydrogen-containing alkyl Grignard reagents in simple ferric salt cross-couplings have been elucidated. The reaction of FeCl3 with EtMgBr in THF leads to the formation of the cluster species [Fe8 Et12 ]2- , a rare example of a structurally characterized metal complex with bridging ethyl ligands. Analogous reactions in the presence of NMP, a key additive for effective cross-coupling with simple ferric salts and β-hydrogen-containing alkyl nucleophiles, result in the formation of [FeEt3 ]- . Reactivity studies demonstrate the effectiveness of [FeEt3 ]- in rapidly and selectively forming the cross-coupled product upon reaction with electrophiles. The identification of iron-ate species with EtMgBr analogous to those previously observed with MeMgBr is a critical insight, indicating that analogous iron species can be operative in catalysis for these two classes of alkyl nucleophiles.
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Affiliation(s)
- Jeffrey D Sears
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Salvador B Muñoz
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Stephanie L Daifuku
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Ari A Shaps
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Stephanie H Carpenter
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - William W Brennessel
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, B31 Hutchison Hall, 120 Trustee Road, Rochester, NY, 14627, USA
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43
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Girigiri PB, Carpenter SH, Brennessel WW, Neidig ML. Crystal structure of bromido-penta-kis-(tetra-hydro-furan-κ O)magnesium bis-[1,2-bis-(di-phenyl-phosphan-yl)benzene-κ 2 P, P']cobaltate(-1) tetra-hydro-furan disolvate. Acta Crystallogr E Crystallogr Commun 2019; 75:304-307. [PMID: 30800472 PMCID: PMC6362642 DOI: 10.1107/s2056989019001671] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 01/29/2019] [Indexed: 11/25/2022]
Abstract
The reduction of CoBr2 by the Grignard reagent p-tolylmagnesium bromide in the presence of 1,2-bis(diphenylphosphanyl)benzene (dbpz) resulted in the d10, formally Co−1 anion, [Co(dpbz)2]−. The crystal structure of the [MgBr(THF)5]+ (THF is tetrahydrofuran) salt showed the anion to be pseudotetrahedral and packed in alternating layers of anions and cations. Structural characterization of the ionic title complex, [MgBr(THF)5][Co(dpbz)2]·2THF [THF is tetrahydrofuran, C4H8O; dpbz is 1,2-bis(diphenylphosphanyl)benzene, C30H24P2], revealed a well-separated cation and anion co-crystallized with two THF solvent molecules that interact with the cation via weak C—H⋯O contacts. The geometry about the cobalt center is pseudotetrahedral, as is expected for a d10 metal center, only deviating from an ideal tetrahedral geometry because of the restrictive bite angles of the bidentate phosphane ligands. Three THF ligands of the cation and one co-crystallized THF solvent molecule are each disordered over two orientations. In the extended structure, the cations and THF solvent molecules are arranged in (100) sheets that alternate with layers of anions, the latter of which show various π-interactions, which may explain the particular packing arrangement.
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Affiliation(s)
| | | | | | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
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Sears JD, Muñoz SB, Daifuku SL, Shaps AA, Carpenter SH, Brennessel WW, Neidig ML. The Effect of β‐Hydrogen Atoms on Iron Speciation in Cross‐Couplings with Simple Iron Salts and Alkyl Grignard Reagents. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201813578] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Jeffrey D. Sears
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Salvador B. Muñoz
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Stephanie L. Daifuku
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Ari A. Shaps
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Stephanie H. Carpenter
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - William W. Brennessel
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
| | - Michael L. Neidig
- Department of Chemistry University of Rochester B31 Hutchison Hall 120 Trustee Road Rochester NY 14627 USA
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Neidig ML, Carpenter SH, Curran DJ, DeMuth JC, Fleischauer VE, Iannuzzi TE, Neate PGN, Sears JD, Wolford NJ. Development and Evolution of Mechanistic Understanding in Iron-Catalyzed Cross-Coupling. Acc Chem Res 2019; 52:140-150. [PMID: 30592421 DOI: 10.1021/acs.accounts.8b00519] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Since the pioneering work of Kochi in the 1970s, iron has attracted great interest for cross-coupling catalysis due to its low cost and toxicity as well as its potential for novel reactivity compared to analogous reactions with precious metals like palladium. Today there are numerous iron-based cross-coupling methodologies available, including challenging alkyl-alkyl and enantioselective methods. Furthermore, cross-couplings with simple ferric salts and additives like NMP and TMEDA ( N-methylpyrrolidone and tetramethylethylenediamine) continue to attract interest in pharmaceutical applications. Despite the tremendous advances in iron cross-coupling methodologies, in situ formed and reactive iron species and the underlying mechanisms of catalysis remain poorly understood in many cases, inhibiting mechanism-driven methodology development in this field. This lack of mechanism-driven development has been due, in part, to the challenges of applying traditional characterization methods such as nuclear magnetic resonance (NMR) spectroscopy to iron chemistry due to the multitude of paramagnetic species that can form in situ. The application of a broad array of inorganic spectroscopic methods (e.g., electron paramagnetic resonance, 57Fe Mössbauer, and magnetic circular dichroism) removes this barrier and has revolutionized our ability to evaluate iron speciation. In conjunction with inorganic syntheses of unstable organoiron intermediates and combined inorganic spectroscopy/gas chromatography studies to evaluate in situ iron reactivity, this approach has dramatically evolved our understanding of in situ iron speciation, reactivity, and mechanisms in iron-catalyzed cross-coupling over the past 5 years. This Account focuses on the key advances made in obtaining mechanistic insight in iron-catalyzed carbon-carbon cross-couplings using simple ferric salts, iron-bisphosphines, and iron- N-heterocyclic carbenes (NHCs). Our studies of ferric salt catalysis have resulted in the isolation of an unprecedented iron-methyl cluster, allowing us to identify a novel reaction pathway and solve a decades-old mystery in iron chemistry. NMP has also been identified as a key to accessing more stable intermediates in reactions containing nucleophiles with and without β-hydrogens. In iron-bisphosphine chemistry, we have identified several series of transmetalated iron(II)-bisphosphine complexes containing mesityl, phenyl, and alkynyl nucleophile-derived ligands, where mesityl systems were found to be unreliable analogues to phenyls. Finally, in iron-NHC cross-coupling, unique chelation effects were observed in cases where nucleophile-derived ligands contained coordinating functional groups. As with the bisphosphine case, high-spin iron(II) complexes were shown to be reactive and selective in cross-coupling. Overall, these studies have demonstrated key aspects of iron cross-coupling and the utility of detailed speciation and mechanistic studies for the rational improvement and development of iron cross-coupling methods.
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Affiliation(s)
- Michael L. Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Stephanie H. Carpenter
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Daniel J. Curran
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Joshua C. DeMuth
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Valerie E. Fleischauer
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Theresa E. Iannuzzi
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Peter G. N. Neate
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Jeffrey D. Sears
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Nikki J. Wolford
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Carpenter SH, Baker TM, Muñoz SB, Brennessel WW, Neidig ML. Multinuclear iron-phenyl species in reactions of simple iron salts with PhMgBr: identification of Fe 4(μ-Ph) 6(THF) 4 as a key reactive species for cross-coupling catalysis. Chem Sci 2018; 9:7931-7939. [PMID: 30429998 PMCID: PMC6201819 DOI: 10.1039/c8sc02915f] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 08/23/2018] [Indexed: 12/25/2022] Open
Abstract
The first direct syntheses, structural characterizations, and reactivity studies of iron-phenyl species formed upon reaction of Fe(acac)3 and PhMgBr in THF are presented. Reaction of Fe(acac)3 with 4 equiv. PhMgBr in THF leads to the formation of [FePh2(μ-Ph)]2 2- at -80 °C, which can be stabilized through the addition of N-methylpyrrolidone. Alternatively, at -30 °C this reaction leads to the formation of the tetranuclear iron-phenyl cluster, Fe4(μ-Ph)6(THF)4. Further synthetic studies demonstrate that analogous tetranuclear iron clusters can be formed with both 4-F-PhMgBr and p-tolylMgBr, illustrating the generality of this structural motif for reactions of simple ferric salts and aryl Grignard reagents in THF. Additional studies isolate and define key iron species involved in the synthetic pathway leading to the formation of the tetranuclear iron-aryl species. While reaction studies demonstrate that [FePh2(μ-Ph)]2 2- is unreactive towards electrophile, Fe4(μ-Ph)6(THF)4 is found to rapidly react with bromocyclohexane to selectively form phenylcyclohexane. Based on this reactivity, a new catalytic reaction protocol has been developed that enables efficient cross-couplings using Fe4(μ-Ph)6(THF)4, circumventing the current need for additives such as TMEDA or supporting ligands to achieve effective cross-coupling of PhMgBr and a secondary alkyl halide.
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Affiliation(s)
- Stephanie H Carpenter
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - Tessa M Baker
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - Salvador B Muñoz
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - William W Brennessel
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - Michael L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
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Abstract
Iron-catalyzed cross-coupling reactions have attracted significant research interest, as they offer numerous favorable features compared with cross-coupling reactions with precious metal catalysis. While this research has contributed to an empirical understanding of iron-catalyzed cross-coupling, the underlying fundamental mechanisms of reaction and structures of catalytically active species have remained poorly defined. The lack of such detail can be attributed to the difficulties associated with studying such iron-catalyzed reactions, where unstable paramagnetic intermediates abound. Recently, the combined application of physical-inorganic spectroscopic methods, concomitant organic product analysis, and air- and temperature-sensitive inorganic synthesis has yielded the most detailed insight currently available on reactivity and mechanism in iron-catalyzed cross-coupling. This Perspective highlights this approach and the limitations of the contributing techniques as well as some of the key features of the catalytic reactions studied and lessons learned.
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Affiliation(s)
- Jeffrey D Sears
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Peter G N Neate
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Michael L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
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Muñoz SB, Fleischauer VE, Brennessel WW, Neidig ML. Combined Effects of Backbone and N-Substituents on Structure, Bonding, and Reactivity of Alkylated Iron(II)-NHCs. Organometallics 2018; 37:3093-3101. [PMID: 30467449 DOI: 10.1021/acs.organomet.8b00466] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Iron and N-heterocyclic carbenes (NHCs) have proven to be a successful pair in catalysis, with reactivity and selectivity being highly dependent on the nature of the NHC ligand backbone saturation and N-substituents. Four (NHC)Fe(1,3-dioxan-2-ylethyl)2 complexes have been isolated and spectroscopically characterized to correlate their reactivity to steric effects of the NHC from both the backbone saturation and N-substituents. Only in the extreme case of SIPr where NHC backbone and N-substituent steric effects are the largest is there a major structural perturbation observed crystallographically. The addition of only two hydrogen atoms is sufficient for a drastic change in product selectivity in the coupling of 1-iodo-3-phenylpropane with (2-(1,3-dioxan-2-yl)ethyl)magnesium bromide due to resulting structural perturbations to the precatalyst. Mössbauer spectroscopy and magnetic circular dichroism enabled the correlation of covalency and steric bulk in the SIPr case to its poor selectivity in alkyl-alkyl cross-coupling with iron. Density functional theory calculations provided insight into the electronic structure and molecular orbital effects of ligation changes to the iron center. Finally, charge donation analysis and Mayer bond order calculations further confirmed the stronger Fe-ligand bonding in the SIPr complex. Overall, these studies highlight the importance of considering both N-substituent and backbone steric contributions to structure, bonding, and reactivity in iron-NHCs.
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Affiliation(s)
- Salvador B Muñoz
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Valerie E Fleischauer
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - William W Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Michael L Neidig
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Li F, Meyer RL, Carpenter SH, VanGelder LE, Nichols AW, Machan CW, Neidig ML, Matson EM. Nitric oxide activation facilitated by cooperative multimetallic electron transfer within an iron-functionalized polyoxovanadate-alkoxide cluster. Chem Sci 2018; 9:6379-6389. [PMID: 30310566 PMCID: PMC6115649 DOI: 10.1039/c8sc00987b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 06/30/2018] [Indexed: 01/06/2023] Open
Abstract
Cooperative multimetallic electron transfer to accommodate substrate binding.
A series of NO-bound, iron-functionalized polyoxovanadate–alkoxide (FePOV–alkoxide) clusters have been synthesized, providing insight into the role of multimetallic constructs in the coordination and activation of a substrate. Upon exposure of the heterometallic cluster to NO, the vanadium-oxide metalloligand is oxidized by a single electron, shuttling the reducing equivalent to the {FeNO} subunit to form a {FeNO}7 species. Four NO-bound clusters with electronic distributions ranging from [VV3VIV2]{FeNO}7 to [VIV5]{FeNO}7 have been synthesized, and characterized via1H NMR, infrared, and electronic absorption spectroscopies. The ability of the FePOV–alkoxide cluster to store reducing equivalents in the metalloligand for substrate coordination and activation highlights the ultility of the metal-oxide scaffold as a redox reservoir.
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Affiliation(s)
- F Li
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - R L Meyer
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - S H Carpenter
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - L E VanGelder
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - A W Nichols
- Department of Chemistry , University of Virginia , Charlottesville , Virginia 22904-4319 , USA
| | - C W Machan
- Department of Chemistry , University of Virginia , Charlottesville , Virginia 22904-4319 , USA
| | - M L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
| | - E M Matson
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , USA .
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Krishnan VM, Davis I, Baker TM, Curran DJ, Arman HD, Neidig ML, Liu A, Tonzetich ZJ. Backbone Dehydrogenation in Pyrrole-Based Pincer Ligands. Inorg Chem 2018; 57:9544-9553. [PMID: 30040391 DOI: 10.1021/acs.inorgchem.8b01643] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Treatment of both [CoCl( tBuPNP)] and [NiCl( tBuPNP)] ( tBuPNP = anion of 2,5-bis((di- tert-butylphosphino)methyl)pyrrole) with one equivalent of benzoquinone affords the corresponding chloride complexes containing a dehydrogenated PNP ligand, tBudPNP ( tBudPNP = anion of 2,5-bis((di- tert-butylphosphino)methylene)-2,5-dihydropyrrole). Dehydrogenation of PNP to dPNP results in minimal change to steric profile of the ligand but has important consequences for the resulting redox potentials of the metal complexes, resulting in the ability to isolate both [CoH( tBudPNP)] and [CoEt( tBudPNP)], which are more challenging (hydride) or not possible (ethyl) to prepare with the parent PNP ligand. Electrochemical measurements with both the Co and Ni dPNP species demonstrate a substantial shift in redox potentials for both the M(II/III) and M(II/I) couples. In the case of the former, oxidation to trivalent Co was found to be reversible, and subsequent reaction with AgSbF6 afforded a rare example of a square-planar Co(III) species. Corresponding reduction of [CoCl( tBudPNP)] with KC8 produced the diamagnetic Co(I) species, [Co(N2)( tBudPNP)]. Further reduction of the Co(I) complex was found to generate a pincer-based π-radical anion that demonstrated well-resolved EPR features to the four hydrogen atoms and lone nitrogen atom of the ligand with minor contributions from cobalt and coordinated N2. Changes in the electronic character of the PNP ligand upon dehydrogenation are proposed to result from loss of aromaticity in the pyrrole ligand, resulting in a more reducing central amido donor. DFT calculations on the Co(II) complexes were performed to shed further insight into the electronic structure of the pincer complexes.
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Affiliation(s)
- V Mahesh Krishnan
- Department of Chemistry , University of Texas at San Antonio (UTSA) , San Antonio , Texas 78249 , United States
| | - Ian Davis
- Department of Chemistry , University of Texas at San Antonio (UTSA) , San Antonio , Texas 78249 , United States
| | - Tessa M Baker
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Daniel J Curran
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Hadi D Arman
- Department of Chemistry , University of Texas at San Antonio (UTSA) , San Antonio , Texas 78249 , United States
| | - Michael L Neidig
- Department of Chemistry , University of Rochester , Rochester , New York 14627 , United States
| | - Aimin Liu
- Department of Chemistry , University of Texas at San Antonio (UTSA) , San Antonio , Texas 78249 , United States
| | - Zachary J Tonzetich
- Department of Chemistry , University of Texas at San Antonio (UTSA) , San Antonio , Texas 78249 , United States
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