1
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Marron DP, Galvin CM, Dressel JM, Waymouth RM. Cobaltocene-Mediated Catalytic Hydride Transfer: Strategies for Electrocatalytic Hydrogenation. J Am Chem Soc 2024; 146:17075-17083. [PMID: 38864712 DOI: 10.1021/jacs.4c02177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2024]
Abstract
The selective electrocatalytic hydrogenation of organics with transition metal hydrides is a promising strategy for electrosynthesis and energy storage. We report the electrocatalytic hydrogenation of acetone with a cyclopentadienone-iridium complex in a tandem electrocatalytic cycle with a cobaltocene mediator. The reductive protonation of cobaltocenium with mild acids generates (C5H5)CoI(C5H6) (CpCoI(CpH)), which functions as an electrocatalytic hydride mediator to deliver a hydride to cationic Ir(III) without generating hydrogen. Electrocatalytic hydride transfer by CpCoI(CpH) to a cationic Ir species leads to the efficient (Faradaic efficiency > 90%) electrohydrogenation of acetone, a valuable hydrogenation target as a liquid organic hydrogen carrier (LOHC). Hydride-transfer mediation presents a powerful strategy to generate metal hydrides that are inaccessible by stepwise electron/proton transfer.
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Affiliation(s)
- Daniel P Marron
- Department of Chemistry, Stanford University, Stanford, California 94306, United States
| | - Conor M Galvin
- Department of Chemistry, Stanford University, Stanford, California 94306, United States
| | - Julia M Dressel
- Department of Chemistry, Stanford University, Stanford, California 94306, United States
| | - Robert M Waymouth
- Department of Chemistry, Stanford University, Stanford, California 94306, United States
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2
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Tanabe Y, Nishibayashi Y. Catalytic Nitrogen Fixation Using Well-Defined Molecular Catalysts under Ambient or Mild Reaction Conditions. Angew Chem Int Ed Engl 2024:e202406404. [PMID: 38781115 DOI: 10.1002/anie.202406404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2024] [Revised: 05/21/2024] [Accepted: 05/23/2024] [Indexed: 05/25/2024]
Abstract
Ammonia (NH3) is industrially produced from dinitrogen (N2) and dihydrogen (H2) by the Haber-Bosch process, although H2 is prepared from fossil fuels, and the reaction requires harsh conditions. On the other hand, microorganisms have fixed nitrogen under ambient reaction conditions. Recently, well-defined molecular transition metal complexes have been found to work as catalyst to convert N2 into NH3 by reactions with chemical reductants and proton sources under ambient reaction conditions. Among them, involvement of both N2-splitting pathway and proton-coupled electron transfer is found to be very effective for high catalytic activity. Furthermore, direct electrocatalytic and photocatalytic conversions of N2 into NH3 have been recently achieved. In addition to catalytic formation of NH3, selective catalytic conversion of N2 into hydrazine (NH2NH2) and catalytic silylation of N2 into silylamines have been reported. Catalytic C-N bond formation has been more recently established to afford cyanate anion (NCO-) under ambient reaction conditions. Further development of direct conversion of N2 into nitrogen-containing compounds as well as green ammonia synthesis leading to the use of ammonia as an energy carrier is expected.
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Affiliation(s)
- Yoshiaki Tanabe
- Department of Applied Chemistry, School of Engineering, The University of Tokyo Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yoshiaki Nishibayashi
- Department of Applied Chemistry, School of Engineering, The University of Tokyo Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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3
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Shen K, Gennari M, Philouze C, Velić A, Demeshko S, Meyer F, Duboc C. Chromium-Thiolate Complex Undergoing C-S Bond Cleavage. Inorg Chem 2024; 63:9119-9128. [PMID: 38709854 DOI: 10.1021/acs.inorgchem.4c00402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
The cleavage of C-S bonds represents a crucial step in fossil fuel refinement to remove organosulfur impurities. Efforts are required to identify alternatives that can replace the energy-intensive hydrodesulfurization process currently in use. In this context, we have developed a series of bis-thiolato-ligated CrIII complexes supported by the L2- ligand (L2- = 2,2'-bipyridine-6,6'-diyl(bis(1,1-diphenylethanethiolate), one of them displaying desulfurization of one thiolate of the ligand under reducing and acidic conditions at ambient temperature and atmospheric pressure. While only 5-coordinated complexes were previously isolated by reaction of L2- with 3d metal MIII ions, both 5- and 6-coordinated mononuclear complexes have been obtained in the case of CrIII, viz., [CrIIILCl], [CrIIILCl2]-, and [CrIIILCl(CH3CN)]. The investigation of the reactivity of [CrIIILCl(CH3CN)] under reducing conditions led to a dinuclear [CrIII2L2(μ-Cl)(μ-OH)] compound and, in the presence of protons, to the mononuclear CrIII complex [CrIII(LN2S)2]+, where LN2S- is the partially desulfurized form of L2-. A desulfurization mechanism has been proposed involving the release of H2S, as evidenced experimentally.
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Affiliation(s)
- Kaiji Shen
- Univ. Grenoble Alpes, CNRS UMR 5250, DCM Grenoble F-38000, France
| | - Marcello Gennari
- Univ. Grenoble Alpes, CNRS UMR 5250, DCM Grenoble F-38000, France
| | | | - Ajdin Velić
- University of Göttingen, Institute of Inorganic Chemistry, Tammannstrasse 4, Göttingen D- 37077, Germany
| | - Serhiy Demeshko
- University of Göttingen, Institute of Inorganic Chemistry, Tammannstrasse 4, Göttingen D- 37077, Germany
| | - Franc Meyer
- University of Göttingen, Institute of Inorganic Chemistry, Tammannstrasse 4, Göttingen D- 37077, Germany
| | - Carole Duboc
- Univ. Grenoble Alpes, CNRS UMR 5250, DCM Grenoble F-38000, France
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4
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Ferrer-Bru C, Ferrer J, Passarelli V, Lahoz FJ, García-Orduña P, Carmona D. Molecular Dihydrogen Activation by (C 5Me 5)M/N (M=Rh, Ir) Transition Metal Frustrated Lewis Pairs: Reversible Proton Migration to, and Proton Abstraction from, the C 5Me 5 Ligand. Chemistry 2024; 30:e202304140. [PMID: 38323731 DOI: 10.1002/chem.202304140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 02/07/2024] [Accepted: 02/07/2024] [Indexed: 02/08/2024]
Abstract
The masked transition-metal frustrated Lewis pairs [Cp*M(κ3N,N',N''-L)][SbF6] (Cp*=η5-C5Me5; M=Ir, 1, Rh, 2; HL=pyridinyl-amidine ligand) reversibly activate H2 under mild conditions rendering the hydrido derivatives [Cp*MH(κ2N,N'-HL)][SbF6] observed as a mixture of the E and Z isomers at the amidine C=N bond (M=Ir, 3Z, 3E; M=Rh, 4Z, 4E). DFT calculations indicate that the formation of the E isomers follows a Grotthuss type mechanism in the presence of water. A mixture of Rh(I) isomers of formula [(Cp*H)Rh(κ2N,N'-HL)][SbF6] (5 a-d) is obtained by reductive elimination of Cp*H from 4. The formation of 5 a-d was elucidated by means of DFT calculations. Finally, when 2 reacts with D2, the Cp* and Cp*H ligands of the resulting rhodium complexes 4 and 5, respectively, are deuterated as a result of a reversible hydrogen abstraction from the Cp* ligand and D2 activation at rhodium.
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Affiliation(s)
- Carlos Ferrer-Bru
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Joaquina Ferrer
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Vincenzo Passarelli
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Fernando J Lahoz
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Pilar García-Orduña
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009, Zaragoza, Spain
| | - Daniel Carmona
- Departamento de Catálisis y Procesos Catalíticos, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC - Universidad de Zaragoza, Departamento de Química Inorgánica, Pedro Cerbuna 12, 50009, Zaragoza, Spain
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5
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Choi H, Yoo S, Song H, Lee E. IZCp and PZCp: Redox Non-innocent Cyclopentadienyl Ligands as Electron Reservoirs for Sandwich Complexes. Inorg Chem 2024; 63:6427-6434. [PMID: 38534011 DOI: 10.1021/acs.inorgchem.4c00259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024]
Abstract
A long-sustained effort of systematic steric and electronic modification of cyclopentadienyl (Cp) ligands has enabled them to find wide-ranging, valuable applications. Herein, we present two novel Cp ligands: imidazolium- and pyrrolinium-substituted zwitterionic Cps (IZCp and PZCp), whose key utility is redox non-innocence─the ability to participate cooperatively with the metal center in redox reactions. Through the simple metalation of ZCps, the Cr(0) and Mo(0) half-sandwich complexes (IZCp)Cr(CO)3, (PZCp)Cr(CO)3, (IZCp)Mo(CO)3, and (PZCp)Mo(CO)3, respectively, as well as the Ru(II) sandwich complexes [(IZCp)RuCp]PF6 and [(PZCp)RuCp]PF6 were prepared. The sandwich complexes were fully characterized and showed by cyclic voltammetry reversible one-electron reduction at E1/2 potentials ranging from -1.7 to -2.7 V vs Fc/Fc+. These values are unusually low and have not been observed with other Cp ligands due to the instability of the reduced complexes. Density functional theory (DFT) calculations for the reduced sandwich derivatives with IZCp and PZCp showed their spin densities to be highly delocalized over their ZCp ligand moieties (70-90%). Electron paramagnetic resonance (EPR) analysis of the isolated K[(PZCp)Mo(CO)3] and (PZCp)RuCp also indicated a high degree of ligand-localized radical character. Thus, the IZCp and PZCp ligands act as electron reservoirs to sustain these sandwich complexes in highly reduced states. At the same time, the CO stretching frequencies of K[(PZCp)Mo(CO)3]: νCO 1871, 1748, and 1699 cm-1, rank the [PZCp]- ligand as the strongest electron-donating Cp ligand among the reported CpMo(CO)3 derivatives, whose νCO > 1746 cm-1. In addition, these redox non-innocent Cps were obtained in high yields and found to be practically air- and moisture-stable, unlike typical Cps.
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Affiliation(s)
- Hyeonjeong Choi
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Seunghyuk Yoo
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
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6
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Johansen C, Peters JC. Catalytic Reduction of Cyanide to Ammonia and Methane at a Mononuclear Fe Site. J Am Chem Soc 2024; 146:5343-5354. [PMID: 38361429 PMCID: PMC10910527 DOI: 10.1021/jacs.3c12395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 01/25/2024] [Accepted: 01/26/2024] [Indexed: 02/17/2024]
Abstract
Nitrogenase enzymes catalyze nitrogen reduction (N2R) to ammonia and also the reduction of non-native substrates, including the 7H+/6e- reduction of cyanide to CH4 and NH3. CN- and N2 are isoelectronic, and it is hence fascinating to compare the mechanisms of synthetic Fe catalysts capable of both CN- and N2 reduction. Here, we describe the catalytic reduction of CN- to NH3 and CH4 by a highly selective (P3Si)Fe(CN) catalyst (P3Si represents a tris(phosphine)silyl ligand). Catalysis is driven in the presence of excess acid ([Ph2NH2]OTf) and reductant ((C6H6)2Cr), with turnover as high as 73 demonstrated. This catalyst system is also modestly competent for N2R and structurally related to other tris(phosphine)Fe-based N2R catalysts. The choice of catalyst and reductant is important to observe high yields. Mechanistic studies elucidate several intermediates of CN- reduction, including iron isocyanides (P3SiFeCNH+/0) and terminal iron aminocarbynes (P3SiFeCNH2+/0). Aminocarbynes are isoelectronic to iron hydrazidos (Fe═N-NH2+/0), which have been invoked as selectivity-determining intermediates of N2R (NH3 versus N2H4 products). For the present CN- reduction catalysis, reduction of aminocarbyne P3SiFeCNH2+ is proposed to be rate but not selectivity contributing. Instead, by comparison with the reactivity of a methylated aminocarbyne analogue (P3SiFeCNMe2), and associated computational studies, formation of a Fischer carbene (P3SiFeC(H)(NH2)+) intermediate that is on path for either CH4 and NH3 (6 e-) or CH3NH2 (4 e-) products is proposed. From this carbene intermediate, pathways to the observed CH4 and NH3 products (distinct from CH3NH2 formation) are considered to compare and contrast the (likely) mechanism/s of CN- and N2 reduction.
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Affiliation(s)
- Christian
M. Johansen
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
| | - Jonas C. Peters
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, Pasadena, California 91125, United States
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7
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Montgomery CL, Amtawong J, Jordan AM, Kurtz DA, Dempsey JL. Proton transfer kinetics of transition metal hydride complexes and implications for fuel-forming reactions. Chem Soc Rev 2023; 52:7137-7169. [PMID: 37750006 DOI: 10.1039/d3cs00355h] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Proton transfer reactions involving transition metal hydride complexes are prevalent in a number of catalytic fuel-forming reactions, where the proton transfer kinetics to or from the metal center can have significant impacts on the efficiency, selectivity, and stability associated with the catalytic cycle. This review correlates the often slow proton transfer rate constants of transition metal hydride complexes to their electronic and structural descriptors and provides perspective on how to exploit these parameters to control proton transfer kinetics to and from the metal center. A toolbox of techniques for experimental determination of proton transfer rate constants is discussed, and case studies where proton transfer rate constant determination informs fuel-forming reactions are highlighted. Opportunities for extending proton transfer kinetic measurements to additional systems are presented, and the importance of synergizing the thermodynamics and kinetics of proton transfer involving transition metal hydride complexes is emphasized.
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Affiliation(s)
- Charlotte L Montgomery
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Jaruwan Amtawong
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Aldo M Jordan
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Daniel A Kurtz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
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8
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Peters JC. Advancing electrocatalytic nitrogen fixation: insights from molecular systems. Faraday Discuss 2023; 243:450-472. [PMID: 37021388 PMCID: PMC10524484 DOI: 10.1039/d3fd00017f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Abstract
Nitrogen fixation has a rich history within the inorganic chemistry community. In recent years attention has (re)focused on developing electrocatalytic systems capable of mediating the nitrogen reduction reaction (N2RR). Well-defined molecular catalyst systems have much to offer in this context. This personal perspective summarizes recent progress from our laboratory at Caltech, pulling together lessons learned from a number of studies we have conducted, placing them within the broader context of thermodynamic efficiency and selectivity for the N2RR. In particular, proton-coupled electron transfer (PCET) provides an attractive strategy to achieve enhanced efficiency for the multi-electron/proton reduction of N2 to produce NH3 (or NH4+), and electrocatalytic PCET (ePCET) via an ePCET mediator affords a promising means of mitigating HER such that the N2RR can be achieved in a catalytic fashion.
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Affiliation(s)
- Jonas C Peters
- California Institute of Technology, Pasadena, CA 91125, USA.
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9
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Boyd EA, Peters JC. Highly Selective Fe-Catalyzed Nitrogen Fixation to Hydrazine Enabled by Sm(II) Reagents with Tailored Redox Potential and p Ka. J Am Chem Soc 2023. [PMID: 37376713 DOI: 10.1021/jacs.3c03352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
Controlling product selectivity in multiproton, multielectron reductions of unsaturated small molecules is of fundamental interest in catalysis. For the N2 reduction reaction (N2RR) in particular, parameters that dictate selectivity for either the 6H+/6e- product ammonia (NH3) or the 4H+/4e- product hydrazine (N2H4) are poorly understood. To probe this issue, we have developed conditions to invert the selectivity of a tris(phosphino)borane iron catalyst (Fe), with which NH3 is typically the major product of N2R, to instead favor N2H4 as the sole observed fixed-N product (>99:1). This dramatic shift is achieved by replacing moderate reductants and strong acids with a very strongly reducing but weakly acidic SmII-(2-pyrrolidone) core supported by a hexadentate dianionic macrocyclic ligand (SmII-PH) as the net hydrogen-atom donor. The activity and efficiency of the catalyst with this reagent remain high (up to 69 equiv of N2H4 per Fe and 67% fixed-N yield per H+). However, by generating N2H4 as the kinetic product, the overpotential of this Sm-driven reaction is 700 mV lower than that of the mildest reported set of NH3-selective conditions with Fe. Mechanistic data support assignment of iron hydrazido(2-) species FeNNH2 as selectivity-determining: we infer that protonation of FeNNH2 at Nβ, favored by strong acids, releases NH3, whereas one-electron reduction to FeNNH2-, favored by strong reductants such as SmII-PH, produces N2H4 via reactivity initiated at Nα. Spectroscopic data also implicate a role for SmIII-binding to anionic FeN2- (via an Fe-N2- -SmIII species) with respect to catalytic efficacy.
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Affiliation(s)
- Emily A Boyd
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
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10
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VanderWeide A, Prokopchuk DE. Cyclopentadienyl ring activation in organometallic chemistry and catalysis. Nat Rev Chem 2023:10.1038/s41570-023-00501-1. [PMID: 37258685 DOI: 10.1038/s41570-023-00501-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2023] [Indexed: 06/02/2023]
Abstract
The cyclopentadienyl (Cp) ligand is a cornerstone of modern organometallic chemistry. Since the discovery of ferrocene, the Cp ligand and its various derivatives have become foundational motifs in catalysis, medicine and materials science. Although largely considered an ancillary ligand for altering the stereoelectronic properties of transition metal centres, there is mounting evidence that the core Cp ring structure also serves as a reservoir for reactive protons (H+), hydrides (H-) or radical hydrogen (H•) atoms. This Review chronicles the field of Cp ring activation, highlighting the pivotal role that Cp ligands can have in electrocatalytic H2 production, N2 reduction, hydride transfer reactions and proton-coupled electron transfer.
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11
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Henke W, Peng Y, Meier A, Fujita E, Grills D, Polyansky D, Blakemore J. Mechanistic roles of metal- and ligand-protonated species in hydrogen evolution with [Cp*Rh] complexes. Proc Natl Acad Sci U S A 2023; 120:e2217189120. [PMID: 37186841 PMCID: PMC10214172 DOI: 10.1073/pnas.2217189120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 02/17/2023] [Indexed: 05/17/2023] Open
Abstract
Protonation reactions involving organometallic complexes are ubiquitous in redox chemistry and often result in the generation of reactive metal hydrides. However, some organometallic species supported by η5-pentamethylcyclopentadienyl (Cp*) ligands have recently been shown to undergo ligand-centered protonation by direct proton transfer from acids or tautomerization of metal hydrides, resulting in the generation of complexes bearing the uncommon η4-pentamethylcyclopentadiene (Cp*H) ligand. Here, time-resolved pulse radiolysis (PR) and stopped-flow spectroscopic studies have been applied to examine the kinetics and atomistic details involved in the elementary electron- and proton-transfer steps leading to complexes ligated by Cp*H, using Cp*Rh(bpy) as a molecular model (where bpy is 2,2'-bipyridyl). Stopped-flow measurements coupled with infrared and UV-visible detection reveal that the sole product of initial protonation of Cp*Rh(bpy) is [Cp*Rh(H)(bpy)]+, an elusive hydride complex that has been spectroscopically and kinetically characterized here. Tautomerization of the hydride leads to the clean formation of [(Cp*H)Rh(bpy)]+. Variable-temperature and isotopic labeling experiments further confirm this assignment, providing experimental activation parameters and mechanistic insight into metal-mediated hydride-to-proton tautomerism. Spectroscopic monitoring of the second proton transfer event reveals that both the hydride and related Cp*H complex can be involved in further reactivity, showing that [(Cp*H)Rh] is not necessarily an off-cycle intermediate, but, instead, depending on the strength of the acid used to drive catalysis, an active participant in hydrogen evolution. Identification of the mechanistic roles of the protonated intermediates in the catalysis studied here could inform design of optimized catalytic systems supported by noninnocent cyclopentadienyl-type ligands.
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Affiliation(s)
- Wade C. Henke
- Department of Chemistry, University of Kansas, Lawrence, KS66045
| | - Yun Peng
- Department of Chemistry, University of Kansas, Lawrence, KS66045
| | - Alex A. Meier
- Department of Chemistry, University of Kansas, Lawrence, KS66045
| | - Etsuko Fujita
- Chemistry Division, Brookhaven National Laboratory, Upton, NY11973-5000
| | - David C. Grills
- Chemistry Division, Brookhaven National Laboratory, Upton, NY11973-5000
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12
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Alférez MG, Moreno JJ, Maya C, Campos J. Polarized Au(I)/Rh(I) bimetallic pairs cooperatively trigger ligand non-innocence and bond activation. Dalton Trans 2023; 52:3835-3845. [PMID: 36866716 PMCID: PMC10029337 DOI: 10.1039/d3dt00410d] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Accepted: 02/21/2023] [Indexed: 02/24/2023]
Abstract
The combination of molecular metallic fragments of contrasting Lewis character offers many possibilities for cooperative bond activation and for the disclosure of unusual reactivity. Here we provide a systematic investigation on the partnership of Lewis basic Rh(I) compounds of type [(η5-L)Rh(PR3)2] (η5-L = (C5Me5)- or (C9H7)-) with highly congested Lewis acidic Au(I) species. For the cyclopentadienyl Rh(I) compounds, we demonstrate the non-innocent role of the typically robust (C5Me5)- ligand through migration of a hydride to the Rh site and provide evidence for the direct implication of the gold fragment in this unusual bimetallic ligand activation event. This process competes with the formation of dinuclear Lewis adducts defined by a dative Rh → Au bond, with selectivity being under kinetic control and tunable by modifying the stereoelectronic and chelating properties of the phosphine ligands bound to the two metals. We provide a thorough computational study on the unusual Cp* non-innocent behavior and the divergent bimetallic pathways observed. The cooperative FLP-type reactivity of all bimetallic pairs has been investigated and computationally examined for the case of N-H bond activation in ammonia.
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Affiliation(s)
- Macarena G Alférez
- Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and University of Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
| | - Juan J Moreno
- Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and University of Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
| | - Celia Maya
- Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and University of Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
| | - Jesús Campos
- Instituto de Investigaciones Químicas (IIQ), Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Consejo Superior de Investigaciones Científicas (CSIC) and University of Sevilla, Avenida Américo Vespucio 49, 41092 Sevilla, Spain.
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13
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Boekell NG, Bartulovich CO, Maity S, Flowers RA. Accessing Unusual Reactivity through Chelation-Promoted Bond Weakening. Inorg Chem 2023; 62:5040-5045. [PMID: 36912617 DOI: 10.1021/acs.inorgchem.3c00298] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
Highly reducing Sm(II) reductants and protic ligands were used as a platform to ascertain the relationship between low-valent metal-protic ligand affinity and degree of ligand X-H bond weakening with the goal of forming potent proton-coupled electron transfer (PCET) reductants. Among the Sm(II)-protic ligand reductant systems investigated, the samarium dibromide N-methylethanolamine (SmBr2-NMEA) reagent system displayed the best combination of metal-ligand affinity and stability against H2 evolution. The use of SmBr2-NMEA afforded the reduction of a range of substrates that are typically recalcitrant to single-electron reduction including alkynes, lactones, and arenes as stable as biphenyl. Moreover, the unique role of NMEA as a chelating ligand for Sm(II) was demonstrated by the reductive cyclization of unactivated esters bearing pendant olefins in contrast to the SmBr2-water-amine system. Finally, the SmBr2-NMEA reagent system was found to reduce substrates analogous to key intermediates in the nitrogen fixation process. These results reveal SmBr2-NMEA to be a powerful reductant for a wide range of challenging substrates and demonstrate the potential for the rational design of PCET reagents with exceptionally weak X-H bonds.
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Affiliation(s)
- Nicholas G Boekell
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Caroline O Bartulovich
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Sandeepan Maity
- Department of Chemistry, C. V. Raman Global University, Bhubaneswar, Odisha 752054, India
| | - Robert A Flowers
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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14
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Aðalsteinsson HM, Bjornsson R. Ionization energies of metallocenes: a coupled cluster study of cobaltocene. Phys Chem Chem Phys 2023; 25:4570-4587. [PMID: 36723003 DOI: 10.1039/d2cp04715b] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Open-shell transition metal chemistry presents challenges to contemporary electronic structure methods, based on either density functional or wavefunction theory. While CCSD(T) is the well-trusted gold standard for maingroup thermochemistry, the accuracy and robustness of the method is less clear for open-shell transition metal chemistry, requiring benchmarking of CCSD(T)-based protocols against either higher-level theory or experiment. Ionization energies (IEs) of metallocenes provide an interesting test case with metallocenes being common redox reagents as well as playing roles as redox mediators and cocatalysts in redox catalysis. Using highly accurate ZEKE-MATI experimental measurements of gas phase adiabatic (5.3275 ± 0.0006 eV) and vertical (5.4424 ± 0.0006 eV) ionization energies of cobaltocene, we systematically assessed the accuracy of the local coupled-cluster method DLPNO-CCSD(T) with respect to geometry, reference determinant, basis set size and extrapolation schemes, PNO cut-off and extrapolation, local triples approximation, relativistic effects and core-valence correlation. We show that PNO errors are controllable via the recently introduced PNO extrapolation schemes and that the expensive iterative triples (T1) contribution can be made more manageable by calculating it as a smaller-basis/smaller PNO-cutoff correction. The reference determinant turns out to be a critical aspect in these calculations with the HF determinant resulting in large DLPNO-CCSD(T) errors, likely due to the qualitatively flawed molecular orbital spectrum. The BP86 functional on the other hand was found to provide reference orbitals giving small DLPNO-CCSD(T) errors, likely due to more realistic orbitals as suggested by the more consistent MO spectrum compared to HF. A protocol including complete basis set extrapolations with correlation-consistent basis sets, complete PNO space extrapolations, iterative triples- and core-valence correlation corrections was found to give errors of -0.07 eV and -0.03 eV for adiabatic- and vertical-IE of cobaltocene, respectively, giving close to chemical accuracy for both properties. A computationally efficient DLPNO-CCSD(T) protocol was devised and tested against adiabatic ionization energies of 6 different metallocenes (V, Cr, Mn, Fe, Co, Ni). For the other metallocenes, the iterative triples (T1) and PNO extrapolation contributions turn out to be even more important. The results give errors close to the experimental uncertainty, similar to recent auxiliary-field quantum Monte Carlo results. The quality of the reference determinant orbitals is identified as the main source of uncertainty in CCSD(T) calculations of metallocenes.
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Affiliation(s)
| | - Ragnar Bjornsson
- Science Institute, University of Iceland, 107 Reykjavik, Iceland.,Univ Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, 17 Rue des Martyrs, F-38054 Grenoble Cedex, France.
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15
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Pal S. Cp* non-innocence and the implications of (η 4-Cp*H)Rh intermediates in the hydrogenation of CO 2, NAD +, amino-borane, and the Cp* framework - a computational study. Dalton Trans 2023; 52:1182-1187. [PMID: 36648493 DOI: 10.1039/d2dt03611h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
In hydrogenation mediated by half-sandwich complexes of Rh, Cp*Rh(III)-H intermediates are critical hydride-delivery agents. For bipyridine-supported complexes, a unique transformation named 'Cp* non-innocence' leads to the appearance of (Cp*H)Rh(I) intermediates, which are purported to exhibit enhanced hydride-delivery capabilities. In this work, DFT calculations performed to compare the role of these complexes in hydrogenation reveal that (Cp*H)Rh(I) intermediates do not compete with the conventional pathway (involving Cp*Rh(III)-H); instead they can lead to sequential hydrogenation of the Cp* framework, and potentially, catalyst degradation. Thus, caution is warranted when invoking the truly homogeneous nature of hydrogenation catalysis mediated by this popular class of complexes.
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Affiliation(s)
- Shrinwantu Pal
- Coordination Chemistry and Catalysis Unit, Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Okinawa, 904-0495, Japan.
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16
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Boyd EA, Peters JC. Sm(II)-Mediated Proton-Coupled Electron Transfer: Quantifying Very Weak N-H and O-H Homolytic Bond Strengths and Factors Controlling Them. J Am Chem Soc 2022; 144:21337-21346. [PMID: 36346706 PMCID: PMC10281198 DOI: 10.1021/jacs.2c09580] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Coordination of alcohols to the single-electron reductant samarium diiodide (SmI2) results in substantial O-H bond weakening, affording potent proton-coupled electron transfer (PCET) reagents. However, poorly defined speciation of SmI2 in tetrahydrofuran (THF)/alcohol mixtures limits reliable thermodynamic analyses of such systems. Rigorous determination of bond dissociation free energy (BDFE) values in such Sm systems, important to evaluating their reactivity profiles, motivates studies of model Sm systems where contributing factors can be teased apart. Here, a bulky and strongly chelating macrocyclic ligand ((tBu2ArOH)2Me2cyclam) maintains solubility, eliminates dimerization pathways, and facilitates clean electrochemical behavior in a well-defined functional model for the PCET reactivity of SmII with coordinating proton sources. Direct measurement of thermodynamic parameters enables reliable experimental estimation of the BDFEs in 2-pyrrolidone and MeOH complexes of ((tBu2ArO)2Me2cyclam)SmII, thereby revealing exceptionally weak N-H and O-H BDFEs of 27.2 and <24.1 kcal mol-1, respectively. Expanded thermochemical cycles reveal that this bond weakening stems from the very strongly reducing SmII center and the formation of strong SmIII-alkoxide (and -pyrrolidonate) interactions in the PCET products. We provide a detailed analysis comparing these BDFE values with those that have been put forward for SmI2 in THF in the presence of related proton donors. We suggest that BDFE values for the latter systems may in fact be appreciably higher than the system described herein. Finally, protonation and electrochemical reduction steps necessary for the regeneration of the PCET donors from SmIII-alkoxides are demonstrated, pointing to future strategies aimed at achieving (electro)catalytic turnover using SmII-based PCET reagents.
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Affiliation(s)
- Emily A Boyd
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
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17
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Ali T, Wang H, Iqbal W, Bashir T, Shah R, Hu Y. Electro-Synthesis of Organic Compounds with Heterogeneous Catalysis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 10:e2205077. [PMID: 36398622 PMCID: PMC9811472 DOI: 10.1002/advs.202205077] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 10/19/2022] [Indexed: 06/16/2023]
Abstract
Electro-organic synthesis has attracted a lot of attention in pharmaceutical science, medicinal chemistry, and future industrial applications in energy storage and conversion. To date, there has not been a detailed review on electro-organic synthesis with the strategy of heterogeneous catalysis. In this review, the most recent advances in synthesizing value-added chemicals by heterogeneous catalysis are summarized. An overview of electrocatalytic oxidation and reduction processes as well as paired electrocatalysis is provided, and the anodic oxidation of alcohols (monohydric and polyhydric), aldehydes, and amines are discussed. This review also provides in-depth insight into the cathodic reduction of carboxylates, carbon dioxide, CC, C≡C, and reductive coupling reactions. Moreover, the electrocatalytic paired electro-synthesis methods, including parallel paired, sequential divergent paired, and convergent paired electrolysis, are summarized. Additionally, the strategies developed to achieve high electrosynthesis efficiency and the associated challenges are also addressed. It is believed that electro-organic synthesis is a promising direction of organic electrochemistry, offering numerous opportunities to develop new organic reaction methods.
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Affiliation(s)
- Tariq Ali
- Key Laboratory of the Ministry of Education for Advanced Catalysis MaterialsDepartment of ChemistryZhejiang Normal UniversityJinhua321004China
| | - Haiyan Wang
- Key Laboratory of the Ministry of Education for Advanced Catalysis MaterialsDepartment of ChemistryZhejiang Normal UniversityJinhua321004China
| | - Waseem Iqbal
- Dipartimento di Chimica e Tecnologie ChimicheUniversità della CalabriaRendeCS87036Italy
| | - Tariq Bashir
- Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy TechnologiesSoochow UniversitySuzhou215006China
| | - Rahim Shah
- Institute of Chemical SciencesUniversity of SwatSwatKhyber Pakhtunkhwa19130Pakistan
| | - Yong Hu
- Key Laboratory of the Ministry of Education for Advanced Catalysis MaterialsDepartment of ChemistryZhejiang Normal UniversityJinhua321004China
- Hangzhou Institute of Advanced StudiesZhejiang Normal UniversityHangzhou311231China
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18
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Kim S, Chen PP, Houk KN, Knowles RR. Reversible Homolysis of a Carbon-Carbon σ-Bond Enabled by Complexation-Induced Bond-Weakening. J Am Chem Soc 2022; 144:15488-15496. [PMID: 35994332 PMCID: PMC9671280 DOI: 10.1021/jacs.2c01229] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A case study of catalytic carbon-carbon σ-bond homolysis is presented. The coordination of a redox-active Lewis acid catalyst reduces the bond-dissociation free energies of adjacent carbon-carbon σ-bonds, and this complexation-induced bond-weakening is used to effect reversible carbon-carbon bond homolysis. Stereochemical isomerization of 1,2-disubstituted cyclopropanes was investigated as a model reaction with a ruthenium (III/II) redox couple adopted for bond weakening. Results from our mechanistic investigation into the stereospecificity of the isomerization reaction are consistent with selective complexation-induced carbon-carbon bond homolysis. The ΔG‡ of catalyzed and uncatalyzed reactions were estimated to be 14.4 and 40.0 kcal/mol, respectively with the computational method, (U)PBE0-D3/def2-TZVPP-SMD(toluene)//(U)B3LYP-D3/def2-SVP. We report this work as the first catalytic example where the complexation-induced bond-weakening effect is quantified through transition state analysis.
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Affiliation(s)
- Suhong Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Pan-Pan Chen
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - K. N. Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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19
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Abstract
Coordination-induced bond weakening is a phenomenon wherein ligand X-H bond homolysis occurs in concert with the energetically favorable oxidation of a coordinating metal complex. The coupling of these two processes enables thermodynamically favorable proton-coupled electron transfer reductions to form weak bonds upon formal hydrogen atom transfer to substrates. Moreover, systems utilizing coordination-induced bond weakening have been shown to facilitate the dehydrogenation of feedstock molecules including water, ammonia, and primary alcohols under mild conditions. The formation of exceptionally weak substrate X-H bonds via small molecule homolysis is a powerful strategy in synthesis and has been shown to enable nitrogen fixation under mild conditions. Coordination-induced bond weakening has also been identified as an integral process in biophotosynthesis and has promising applications in renewable chemical fuel storage systems. This review presents a discussion of the advances made in the study of coordination-induced bond weakening to date. Because of the broad range of metal and ligand species implicated in coordination-induced bond weakening, each literature report is discussed individually and ordered by the identity of the low-valent metal. We then offer mechanistic insights into the basis of coordination-induced bond weakening and conclude with a discussion of opportunities for further research into the development and applications of coordination-induced bond weakening systems.
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Affiliation(s)
- Nicholas G Boekell
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Robert A Flowers
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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20
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Waniek SD, Heine C, Zorn D, Lieberth T, Lauck M, Förster C, Heinze K. Dicobaltocenium Amine–Proton, Electron, and H Atom Transfer. Organometallics 2022. [DOI: 10.1021/acs.organomet.2c00211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sven D. Waniek
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
| | - Christian Heine
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
| | - Dimitri Zorn
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
| | - Taro Lieberth
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
| | - Maximilian Lauck
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
| | - Christoph Förster
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
| | - Katja Heinze
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, D-55128 Mainz, Germany
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21
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Connor GP, Delony D, Weber JE, Mercado BQ, Curley JB, Schneider S, Mayer JM, Holland PL. Facile conversion of ammonia to a nitride in a rhenium system that cleaves dinitrogen. Chem Sci 2022; 13:4010-4018. [PMID: 35440977 PMCID: PMC8985503 DOI: 10.1039/d1sc04503b] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Accepted: 02/22/2022] [Indexed: 11/21/2022] Open
Abstract
Rhenium complexes with aliphatic PNP pincer ligands have been shown to be capable of reductive N2 splitting to nitride complexes. However, the conversion of the resulting nitride to ammonia has not been observed. Here, the thermodynamics and mechanism of the hypothetical N–H bond forming steps are evaluated through the reverse reaction, conversion of ammonia to the nitride complex. Depending on the conditions, treatment of a rhenium(iii) precursor with ammonia gives either a bis(amine) complex [(PNP)Re(NH2)2Cl]+, or results in dehydrohalogenation to the rhenium(iii) amido complex, (PNP)Re(NH2)Cl. The N–H hydrogen atoms in this amido complex can be abstracted by PCET reagents which implies that they are quite weak. Calorimetric measurements show that the average bond dissociation enthalpy of the two amido N–H bonds is 57 kcal mol−1, while DFT computations indicate a substantially weaker N–H bond of the putative rhenium(iv)-imide intermediate (BDE = 38 kcal mol−1). Our analysis demonstrates that addition of the first H atom to the nitride complex is a thermochemical bottleneck for NH3 generation. Rhenium–PNP complexes split N2 to nitrides, but the nitrides do not give ammonia. Here, the thermodynamics of the hypothetical N–H bond forming steps are evaluated through the reverse reaction, showing that the first H addition is the bottleneck.![]()
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Affiliation(s)
- Gannon P Connor
- Department of Chemistry, Yale University New Haven Connecticut USA
| | - Daniel Delony
- Institute of Inorganic Chemistry, Georg-August-Universität Göttingen Göttingen Germany
| | - Jeremy E Weber
- Department of Chemistry, Yale University New Haven Connecticut USA
| | | | - Julia B Curley
- Department of Chemistry, Yale University New Haven Connecticut USA
| | - Sven Schneider
- Institute of Inorganic Chemistry, Georg-August-Universität Göttingen Göttingen Germany
| | - James M Mayer
- Department of Chemistry, Yale University New Haven Connecticut USA
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22
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Lin L, Wang Y, Xu L. Charge and Configuration Evolution of Intermetalloid Clusters [(Ge9)2M]q− (M/q = Ge/4, In/5, Cd/6, and K/7). Organometallics 2022. [DOI: 10.1021/acs.organomet.1c00697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lifang Lin
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yi Wang
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
| | - Li Xu
- State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
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23
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Agarwal RG, Coste SC, Groff BD, Heuer AM, Noh H, Parada GA, Wise CF, Nichols EM, Warren JJ, Mayer JM. Free Energies of Proton-Coupled Electron Transfer Reagents and Their Applications. Chem Rev 2021; 122:1-49. [PMID: 34928136 DOI: 10.1021/acs.chemrev.1c00521] [Citation(s) in RCA: 131] [Impact Index Per Article: 43.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We present an update and revision to our 2010 review on the topic of proton-coupled electron transfer (PCET) reagent thermochemistry. Over the past decade, the data and thermochemical formalisms presented in that review have been of value to multiple fields. Concurrently, there have been advances in the thermochemical cycles and experimental methods used to measure these values. This Review (i) summarizes those advancements, (ii) corrects systematic errors in our prior review that shifted many of the absolute values in the tabulated data, (iii) provides updated tables of thermochemical values, and (iv) discusses new conclusions and opportunities from the assembled data and associated techniques. We advocate for updated thermochemical cycles that provide greater clarity and reduce experimental barriers to the calculation and measurement of Gibbs free energies for the conversion of X to XHn in PCET reactions. In particular, we demonstrate the utility and generality of reporting potentials of hydrogenation, E°(V vs H2), in almost any solvent and how these values are connected to more widely reported bond dissociation free energies (BDFEs). The tabulated data demonstrate that E°(V vs H2) and BDFEs are generally insensitive to the nature of the solvent and, in some cases, even to the phase (gas versus solution). This Review also presents introductions to several emerging fields in PCET thermochemistry to give readers windows into the diversity of research being performed. Some of the next frontiers in this rapidly growing field are coordination-induced bond weakening, PCET in novel solvent environments, and reactions at material interfaces.
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Affiliation(s)
- Rishi G Agarwal
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Scott C Coste
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Benjamin D Groff
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Abigail M Heuer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Hyunho Noh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Giovanny A Parada
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.,Department of Chemistry, The College of New Jersey, Ewing, New Jersey 08628, United States
| | - Catherine F Wise
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Eva M Nichols
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Jeffrey J Warren
- Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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24
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Sánchez P, Goel B, Neugebauer H, Lalancette RA, Grimme S, Hansen A, Prokopchuk DE. Ligand Protonation at Carbon, not Nitrogen, during H 2 Production with Amine-Rich Iron Electrocatalysts. Inorg Chem 2021; 60:17407-17413. [PMID: 34735115 DOI: 10.1021/acs.inorgchem.1c03142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We present monometallic H2 production electrocatalysts containing electron-rich triamine-cyclopentadienyl (Cp) ligands coordinated to iron. After selective CO extrusion from the iron tricarbonyl precursors, electrocatalysis is observed via cyclic voltammetry in the presence of an exogenous acid. Contrary to the fact that amines in the secondary coordination sphere are often protonated during electrocatalysis, comprehensive quantum-chemical calculations indicate that the amines likely do not function as proton relays; instead, endo-Cp ring protonation is most favorable after 1e- reduction. This unusual mechanistic pathway emphasizes the need to consider a broad domain of H+/e- addition products by synergistically combining experimental and theoretical resources.
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Affiliation(s)
- Práxedes Sánchez
- Department of Chemistry, Rutgers University─Newark, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Bhumika Goel
- Department of Chemistry, Rutgers University─Newark, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Hagen Neugebauer
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn, Beringstraße 4, Bonn 53115, Germany
| | - Roger A Lalancette
- Department of Chemistry, Rutgers University─Newark, 73 Warren Street, Newark, New Jersey 07102, United States
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn, Beringstraße 4, Bonn 53115, Germany
| | - Andreas Hansen
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn, Beringstraße 4, Bonn 53115, Germany
| | - Demyan E Prokopchuk
- Department of Chemistry, Rutgers University─Newark, 73 Warren Street, Newark, New Jersey 07102, United States
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25
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Gardner EJ, Marguet SC, Cobb CR, Pham DM, Beringer JAM, Bertke JA, Shafaat HS, Warren TH. Uncovering Redox Non-innocent Hydrogen-Bonding in Cu(I)-Diazene Complexes. J Am Chem Soc 2021; 143:15960-15974. [PMID: 34546737 DOI: 10.1021/jacs.1c04108] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The life-sustaining reduction of N2 to NH3 is thermoneutral yet kinetically challenged by high-energy intermediates such as N2H2. Exploring intramolecular H-bonding as a potential strategy to stabilize diazene intermediates, we employ a series of [xHetTpCu]2(μ-N2H2) complexes that exhibit H-bonding between pendant aromatic N-heterocycles (xHet) such as pyridine and a bridging trans-N2H2 ligand at copper(I) centers. X-ray crystallography and IR spectroscopy clearly reveal H-bonding in [pyMeTpCu]2(μ-N2H2) while low-temperature 1H NMR studies coupled with DFT analysis reveals a dynamic equilibrium between two closely related, symmetric H-bonded structural motifs. Importantly, the xHet pendant negligibly influences the electronic structure of xHetTpCuI centers in xHetTpCu(CNAr2,6-Me2) complexes that lack H-bonding as judged by nearly indistinguishable ν(CN) frequencies (2113-2117 cm-1). Nonetheless, H-bonding in the corresponding [xHetTpCu]2(μ-N2H2) complexes results in marked changes in ν(NN) (1398-1419 cm-1) revealed through resonance Raman studies. Due to the closely matched N-H BDEs of N2H2 and the pyH0 cation radical, the aromatic N-heterocyclic pendants may encourage partial H-atom transfer (HAT) from N2H2 to xHet through redox-non-innocent H-bonding in [xHetTpCu]2(μ-N2H2). DFT studies reveal modest thermodynamic barriers for concerted transfer of both H-atoms of coordinated N2H2 to the xHet pendants to generate tautomeric [xHetHTpCu]2(μ-N2) complexes, identifying metal-assisted concerted dual HAT as a thermodynamically favorable pathway for N2/N2H2 interconversion.
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Affiliation(s)
- Evan J Gardner
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Sean C Marguet
- The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Caitlyn R Cobb
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Dominic M Pham
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Josalyne A M Beringer
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Jeffery A Bertke
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Hannah S Shafaat
- The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Timothy H Warren
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
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26
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Moreno JJ, Espada MF, Maya C, Campos J, López-Serrano J, Macgregor SA, Carmona E. Isomerization of a cationic (η5-C5Me5)Ir(III) complex involving remote C–C and C–H bond formation. Polyhedron 2021. [DOI: 10.1016/j.poly.2021.115363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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27
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Wolff N, Rivada‐Wheelaghan O, Tocqueville D. Molecular Electrocatalytic Hydrogenation of Carbonyls and Dehydrogenation of Alcohols. ChemElectroChem 2021. [DOI: 10.1002/celc.202100617] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Niklas Wolff
- Laboratoire d'Électrochimie Moléculaire Université de Paris, CNRS F-75006 Paris France
| | | | - Damien Tocqueville
- Laboratoire d'Électrochimie Moléculaire Université de Paris, CNRS F-75006 Paris France
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28
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Schneck F, Finger M, Siewert I, Schneider S. Solvent dependent C−H Bond Strength in a Nickel Pincer Complex. Z Anorg Allg Chem 2021. [DOI: 10.1002/zaac.202100077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Felix Schneck
- Universität Göttingen Institut für Anorganische Chemie Tammannstraße 4 37077 Göttingen Germany
| | - Markus Finger
- Universität Göttingen Institut für Anorganische Chemie Tammannstraße 4 37077 Göttingen Germany
| | - Inke Siewert
- Universität Göttingen Institut für Anorganische Chemie Tammannstraße 4 37077 Göttingen Germany
| | - Sven Schneider
- Universität Göttingen Institut für Anorganische Chemie Tammannstraße 4 37077 Göttingen Germany
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29
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von Wolff N, Robert M. Taming Electron Transfers: From Breaking Bonds to Creating Molecules. CHEM REC 2021; 21:2095-2106. [PMID: 34235842 DOI: 10.1002/tcr.202100151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 11/07/2022]
Abstract
The electron is the ultimate redox reagent to build and reshape molecular structures. Understanding and controlling the parameters underlying dissociative electron transfer (DET) reactivity and its coupling with proton transfer is crucial for combining selectivity, kinetics and energy efficiency in molecular chemistry. Reactivity understanding and mechanistic elements in DET processes are traced back and key examples of current research efforts are presented, demonstrating a large variety of applications. The involvement of DET pathways indeed encompasses a broad range of processes such as photoredox catalysis, CO2 reduction and alcohol oxidation. Interplay between these experimental examples and fundamental mechanistic study provides a powerful path to the understanding of driving force-rate relationships, which is crucial for the development of future generations of energy efficient catalytic schemes in redox organic chemistry.
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Affiliation(s)
- Niklas von Wolff
- Université de Paris, Laboratoire d'Électrocimie Moléculaire, CNRS, F-75006, Paris, France
| | - Marc Robert
- Université de Paris, Laboratoire d'Électrocimie Moléculaire, CNRS, F-75006, Paris, France.,Institut Universitaire de France (IUF), F-75005, Paris, France
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30
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Zurakowski JA, Austen BJH, Drover MW. Wrapping Rhodium in a Borane Canopy: Implications for Hydride Formation and Transfer. Organometallics 2021. [DOI: 10.1021/acs.organomet.1c00194] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joseph A. Zurakowski
- Department of Chemistry and Biochemistry, The University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
| | - Brady J. H. Austen
- Department of Chemistry and Biochemistry, The University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
| | - Marcus W. Drover
- Department of Chemistry and Biochemistry, The University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada
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31
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Derosa J, Garrido-Barros P, Peters JC. Electrocatalytic Reduction of C-C π-Bonds via a Cobaltocene-Derived Concerted Proton-Electron Transfer Mediator: Fumarate Hydrogenation as a Model Study. J Am Chem Soc 2021; 143:9303-9307. [PMID: 34138550 DOI: 10.1021/jacs.1c03335] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reductive concerted proton-electron transfer (CPET) is poorly developed for the reduction of C-C π-bonds, including for activated alkenes that can succumb to deleterious pathways (e.g., a competing hydrogen evolution reaction or oligomerization) in a standard electrochemical reduction. We demonstrate herein that selective hydrogenation of the C-C π-bond of fumarate esters can be achieved via electrocatalytic CPET (eCPET) using a CPET mediator comprising cobaltocene with a tethered Brønsted base. High selectivity for electrocatalytic hydrogenation is observed only when the mediator is present. Mechanistic analysis sheds light on two distinct kinetic regimes based on the substrate concentration: low fumarate concentrations operate via rate-limiting CPET followed by an electron-transfer/proton-transfer (ET/PT) step, whereas high concentrations operate via CPET followed by a rate-limiting ET/PT step.
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Affiliation(s)
- Joseph Derosa
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
| | - Pablo Garrido-Barros
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
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32
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Marrone A, Fish RH. DFT Mechanism Studies: Biomimetic 1,4-NADH Chemoselective, Co-factor Regeneration with [Cp*Rh(bpy)H]+, in Tandem with the Biocatalysis Pathways of a Core Model of the (HLADH)-Zn(II) Mediated Enzyme, in the Enantioselective Reduction of Achiral Ketones to Chiral S-Alcohols. J Organomet Chem 2021. [DOI: 10.1016/j.jorganchem.2021.121810] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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33
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Tanabe Y, Nishibayashi Y. Comprehensive insights into synthetic nitrogen fixation assisted by molecular catalysts under ambient or mild conditions. Chem Soc Rev 2021; 50:5201-5242. [PMID: 33651046 DOI: 10.1039/d0cs01341b] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
N2 is fixed as NH3 industrially by the Haber-Bosch process under harsh conditions, whereas biological nitrogen fixation is achieved under ambient conditions, which has prompted development of alternative methods to fix N2 catalyzed by transition metal molecular complexes. Since the early 21st century, catalytic conversion of N2 into NH3 under ambient conditions has been achieved by using molecular catalysts, and now H2O has been utilized as a proton source with turnover frequencies reaching the values found for biological nitrogen fixation. In this review, recent advances in the development of molecular catalysts for synthetic N2 fixation under ambient or mild conditions are summarized, and potential directions for future research are also discussed.
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Affiliation(s)
- Yoshiaki Tanabe
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
| | - Yoshiaki Nishibayashi
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
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34
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Kuriyama S, Nishibayashi Y. Development of catalytic nitrogen fixation using transition metal complexes not relevant to nitrogenases. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.131986] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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35
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Kurtz DA, Dhar D, Elgrishi N, Kandemir B, McWilliams SF, Howland WC, Chen CH, Dempsey JL. Redox-Induced Structural Reorganization Dictates Kinetics of Cobalt(III) Hydride Formation via Proton-Coupled Electron Transfer. J Am Chem Soc 2021; 143:3393-3406. [DOI: 10.1021/jacs.0c11992] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Daniel A. Kurtz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Debanjan Dhar
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Noémie Elgrishi
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, Louisiana 70803, United States
| | - Banu Kandemir
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Sean F. McWilliams
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - William C. Howland
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Chun-Hsing Chen
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Jillian L. Dempsey
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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36
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Kuo JL, Goldberg KI. Metal/Ligand Proton Tautomerism Facilitates Dinuclear H 2 Reductive Elimination. J Am Chem Soc 2020; 142:21439-21449. [PMID: 33297680 DOI: 10.1021/jacs.0c10458] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using the doubly protic bis-pyrazole-pyridine ligand (N(NNH)2), we have synthesized an octahedral IrIII-H [HIr(κ3-N(NNH)(NN-))(CO)(tBuPy)]+ ([1-MH]+) from an IrI starting material. This hydride was generated by adding sufficient electron density to the metal center such that it became the thermodynamically preferred site of protonation. It was observed via UV-vis spectroscopy that [1-MH]+ establishes a [tBuPy] dependent equilibrium with a ligand protonated square-planar IrI [Ir(N(NNH)2)(CO)]+ ([2-LH]+). This example of metal/ligand proton tautomerism is unusual in that the position of the equilibrium can be controlled by the concentration of exogeneous ligand (i.e., tBuPy). This equilibrium was shown to be key to the reactivity of the IrIII-H; 2 equiv of [1-MH]+ release H2, converting to the IrII dimer [[Ir(N(NN-)(NNH))(CO)(tBuPy)]2]2+ ([7]2+) under mild conditions (observable at room temperature). Mechanistic evidence is presented to support that this dinuclear reductive elimination occurs by tautomerization of the metal hydride [1-MH]+ to a ligand protonated species [1-LH]+, from which ligand dissociation is facile, generating [2-LH]+. Subsequent reaction of [2-LH]+ with [1-MH]+ allows for production of H2 and the IrII dimer [7]2+. The tautomerization between the metal-hydride and the ligand protonated species provides a low energy pathway for ligand dissociation, opening the needed coordination site. The ability to control the interconversion between a metal-hydride and a ligand-protonated congener using an exogeneous ligand introduces a new strategy for catalyst design with proton responsive ligands.
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Affiliation(s)
- Jonathan L Kuo
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Karen I Goldberg
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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37
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Hirscher NA, Arnett CH, Oyala PH, Agapie T. Characterization of Cr-Hydrocarbyl Species via Pulse EPR in the Study of Ethylene Tetramerization Catalysis. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00521] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nathanael A. Hirscher
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Charles H. Arnett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Paul H. Oyala
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
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38
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Armstrong KC, Waymouth RM. Electroreduction of Benzaldehyde with a Metal–Ligand Bifunctional Hydroxycyclopentadienyl Molybdenum(II) Hydride. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00630] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Keith C. Armstrong
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Robert M. Waymouth
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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39
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Alférez MG, Moreno JJ, Hidalgo N, Campos J. Reversible Hydride Migration from C 5Me 5 to Rh I Revealed by a Cooperative Bimetallic Approach. Angew Chem Int Ed Engl 2020; 59:20863-20867. [PMID: 33448577 PMCID: PMC7754342 DOI: 10.1002/anie.202008442] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/16/2020] [Indexed: 02/06/2023]
Abstract
The use of cyclopentadienyl ligands in organometallic chemistry and catalysis is ubiquitous, mostly due to their robust spectator role. Nonetheless, increasing examples of non-innocent behaviour are being documented. Here, we provide evidence for reversible intramolecular C-H activation at one methyl terminus of C5Me5 in [(η-C5Me5)Rh(PMe3)2] to form a new Rh-H bond, a process so far restricted to early transition metals. Experimental evidence was acquired from bimetallic rhodium/gold structures in which the gold center binds either to the rhodium atom or to the activated Cp* ring. Reversibility of the C-H activation event regenerates the RhI and AuI monometallic precursors, whose cooperative reactivity towards polar E-H bonds (E=O, N), including the N-H bonds in ammonia, can be understood in terms of bimetallic frustration.
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Affiliation(s)
- Macarena G. Alférez
- Instituto de Investigaciones Químicas (IIQ)Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA)Consejo Superior de Investigaciones Científicas (CSIC)University of SevillaAvenida Américo Vespucio 4941092SevillaSpain
| | - Juan J. Moreno
- Instituto de Investigaciones Químicas (IIQ)Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA)Consejo Superior de Investigaciones Científicas (CSIC)University of SevillaAvenida Américo Vespucio 4941092SevillaSpain
| | - Nereida Hidalgo
- Instituto de Investigaciones Químicas (IIQ)Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA)Consejo Superior de Investigaciones Científicas (CSIC)University of SevillaAvenida Américo Vespucio 4941092SevillaSpain
| | - Jesús Campos
- Instituto de Investigaciones Químicas (IIQ)Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA)Consejo Superior de Investigaciones Científicas (CSIC)University of SevillaAvenida Américo Vespucio 4941092SevillaSpain
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40
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Alférez MG, Moreno JJ, Hidalgo N, Campos J. Reversible Hydride Migration from C
5
Me
5
to Rh
I
Revealed by a Cooperative Bimetallic Approach. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202008442] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Macarena G. Alférez
- Instituto de Investigaciones Químicas (IIQ) Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA) Consejo Superior de Investigaciones Científicas (CSIC) University of Sevilla Avenida Américo Vespucio 49 41092 Sevilla Spain
| | - Juan J. Moreno
- Instituto de Investigaciones Químicas (IIQ) Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA) Consejo Superior de Investigaciones Científicas (CSIC) University of Sevilla Avenida Américo Vespucio 49 41092 Sevilla Spain
| | - Nereida Hidalgo
- Instituto de Investigaciones Químicas (IIQ) Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA) Consejo Superior de Investigaciones Científicas (CSIC) University of Sevilla Avenida Américo Vespucio 49 41092 Sevilla Spain
| | - Jesús Campos
- Instituto de Investigaciones Químicas (IIQ) Departamento de Química Inorgánica and Centro de Innovación en Química Avanzada (ORFEO-CINQA) Consejo Superior de Investigaciones Científicas (CSIC) University of Sevilla Avenida Américo Vespucio 49 41092 Sevilla Spain
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41
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Schild DJ, Drover MW, Oyala PH, Peters JC. Generating Potent C-H PCET Donors: Ligand-Induced Fe-to-Ring Proton Migration from a Cp*Fe III-H Complex Demonstrates a Promising Strategy. J Am Chem Soc 2020; 142:18963-18970. [PMID: 33103877 DOI: 10.1021/jacs.0c09363] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Highly reactive organometallic species that mediate reductive proton-coupled electron transfer (PCET) reactions are an exciting area for development in catalysis, where a key objective focuses on tuning the reactivity of such species. This work pursues ligand-induced activation of a stable organometallic complex toward PCET reactivity. This is studied via the conversion of a prototypical Cp*FeIII-H species, [FeIII(η5-Cp*)(dppe)H]+ (Cp* = C5Me5-, dppe = 1,2-bis(diphenylphosphino)ethane), to a highly reactive, S = 1/2 ring-protonated endo-Cp*H-Fe relative, triggered by the addition of CO. Our assignment of the latter ring-protonated species contrasts with its previous reported formulation, which instead assigned it as a hypervalent 19-electron hydride, [FeIII(η5-Cp*)(dppe)(CO)H]+. Herein, pulse EPR spectroscopy (1,2H HYSCORE, ENDOR) and X-ray crystallography, with corresponding DFT studies, cement its assignment as the ring-protonated isomer, [FeI(endo-η4-Cp*H)(dppe)(CO)]+. A less sterically shielded and hence more reactive exo-isomer can be generated through oxidation of a stable Fe0(exo-η4-Cp*H)(dppe)(CO) precursor. Both endo- and exo-ring-protonated isomers are calculated to have an exceptionally low bond dissociation free energy (BDFEC-H ≈ 29 kcal mol-1 and 25 kcal mol-1, respectively) cf. BDFEFe-H of 56 kcal mol-1 for [FeIII(η5-Cp*)(dppe)H]+. These weak C-H bonds are shown to undergo proton-coupled electron transfer (PCET) to azobenzene to generate diphenylhydrazine and the corresponding closed-shell [FeII(η5-Cp*)(dppe)CO]+ byproduct.
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Affiliation(s)
- Dirk J Schild
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Marcus W Drover
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Paul H Oyala
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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42
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Bezdek MJ, Pelczer I, Chirik PJ. Coordination-Induced N–H Bond Weakening in a Molybdenum Pyrrolidine Complex: Isotopic Labeling Provides Insight into the Pathway for H 2 Evolution. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00471] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Máté J. Bezdek
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - István Pelczer
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J. Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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43
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Sondermann C, Pižl M, Paretzki A, Feil C, Ringenberg MR, Záliš S, Kaim W. Analysis of a Diimine‐Organonickel Redox Series. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.202000455] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Christina Sondermann
- Institut für Anorganische Chemie Universität Stuttgart Pfaffenwaldring 55 70550 Stuttgart Germany
| | - Martin Pižl
- J. Heyrovský Institute of Physical Chemistry The Czech Academy of Sciences Dolejškova 3 18223 Prague Czech Republic
- University of Chemistry and Technology Technická 5 166 28 Prague 6 Czech Republic
| | - Alexa Paretzki
- Institut für Anorganische Chemie Universität Stuttgart Pfaffenwaldring 55 70550 Stuttgart Germany
| | - Christoph Feil
- Institut für Anorganische Chemie Universität Stuttgart Pfaffenwaldring 55 70550 Stuttgart Germany
| | - Mark R. Ringenberg
- Institut für Anorganische Chemie Universität Stuttgart Pfaffenwaldring 55 70550 Stuttgart Germany
| | - Stanislav Záliš
- J. Heyrovský Institute of Physical Chemistry The Czech Academy of Sciences Dolejškova 3 18223 Prague Czech Republic
| | - Wolfgang Kaim
- Institut für Anorganische Chemie Universität Stuttgart Pfaffenwaldring 55 70550 Stuttgart Germany
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44
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Chalkley MJ, Garrido-Barros P, Peters JC. A molecular mediator for reductive concerted proton-electron transfers
via electrocatalysis. Science 2020; 369:850-854. [DOI: 10.1126/science.abc1607] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 06/24/2020] [Indexed: 12/16/2022]
Abstract
Electrocatalytic approaches to the activation of unsaturated substrates
via reductive concerted proton-electron transfer (CPET) must overcome
competing, often kinetically dominant hydrogen evolution. We introduce the
design of a molecular mediator for electrochemically triggered reductive
CPET through the synthetic integration of a Brønsted acid and a redox
mediator. Cathodic reduction at the cobaltocenium redox mediator
substantially weakens the homolytic nitrogen-hydrogen bond strength of a
Brønsted acidic anilinium tethered to one of the cyclopentadienyl rings. The
electrochemically generated molecular mediator is demonstrated to transform
a model substrate, acetophenone, to its corresponding neutral α-radical via
a rate-determining CPET.
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Affiliation(s)
- Matthew J. Chalkley
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Pablo Garrido-Barros
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Jonas C. Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
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45
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Bruch QJ, Connor GP, McMillion ND, Goldman AS, Hasanayn F, Holland PL, Miller AJM. Considering Electrocatalytic Ammonia Synthesis via Bimetallic Dinitrogen Cleavage. ACS Catal 2020. [DOI: 10.1021/acscatal.0c02606] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Quinton J. Bruch
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Gannon P. Connor
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Noah D. McMillion
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Alan S. Goldman
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08903, United States
| | - Faraj Hasanayn
- Department of Chemistry, American University of Beirut, Beirut 1107 2020, Lebanon
| | - Patrick L. Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Alexander J. M. Miller
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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46
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Reiners M, Baabe D, Münster K, Zaretzke MK, Freytag M, Jones PG, Coppel Y, Bontemps S, Rosal ID, Maron L, Walter MD. NH 3 formation from N 2 and H 2 mediated by molecular tri-iron complexes. Nat Chem 2020; 12:740-746. [PMID: 32601410 DOI: 10.1038/s41557-020-0483-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 05/05/2020] [Indexed: 01/27/2023]
Abstract
Living systems carry out the reduction of N2 to ammonia (NH3) through a series of protonation and electron transfer steps under ambient conditions using the enzyme nitrogenase. In the chemical industry, the Haber-Bosch process hydrogenates N2 but requires high temperatures and pressures. Both processes rely on iron-based catalysts, but molecular iron complexes that promote the formation of NH3 on addition of H2 to N2 have remained difficult to devise. Here, we isolate the tri(iron)bis(nitrido) complex [(Cp'Fe)3(μ3-N)2] (in which Cp' = η5-1,2,4-(Me3C)3C5H2), which is prepared by reduction of [Cp'Fe(μ-I)]2 under an N2 atmosphere and comprises three iron centres bridged by two μ3-nitrido ligands. In solution, this complex reacts with H2 at ambient temperature (22 °C) and low pressure (1 or 4 bar) to form NH3. In the solid state, it is converted into the tri(iron)bis(imido) species, [(Cp'Fe)3(μ3-NH)2], by addition of H2 (10 bar) through an unusual solid-gas, single-crystal-to-single-crystal transformation. In solution, [(Cp'Fe)3(μ3-NH)2] further reacts with H2 or H+ to form NH3.
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Affiliation(s)
- Matthias Reiners
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany
| | - Dirk Baabe
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany
| | - Katharina Münster
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany
| | - Marc-Kevin Zaretzke
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany
| | - Matthias Freytag
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany
| | - Peter G Jones
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany
| | - Yannick Coppel
- CNRS, LCC (Laboratoire de Chimie de Coordination), Université de Toulouse, UPS, INPT, Toulouse, France
| | - Sébastien Bontemps
- CNRS, LCC (Laboratoire de Chimie de Coordination), Université de Toulouse, UPS, INPT, Toulouse, France
| | - Iker Del Rosal
- Université de Toulouse, INSA-UPS-LPCNO and CNRS-LPCNO, Toulouse, France
| | - Laurent Maron
- Université de Toulouse, INSA-UPS-LPCNO and CNRS-LPCNO, Toulouse, France
| | - Marc D Walter
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Braunschweig, Germany.
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47
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Kim S, Loose F, Chirik PJ. Beyond Ammonia: Nitrogen–Element Bond Forming Reactions with Coordinated Dinitrogen. Chem Rev 2020; 120:5637-5681. [DOI: 10.1021/acs.chemrev.9b00705] [Citation(s) in RCA: 100] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sangmin Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Florian Loose
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J. Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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48
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Chalkley MJ, Drover MW, Peters JC. Catalytic N 2-to-NH 3 (or -N 2H 4) Conversion by Well-Defined Molecular Coordination Complexes. Chem Rev 2020; 120:5582-5636. [PMID: 32352271 DOI: 10.1021/acs.chemrev.9b00638] [Citation(s) in RCA: 178] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nitrogen fixation, the six-electron/six-proton reduction of N2, to give NH3, is one of the most challenging and important chemical transformations. Notwithstanding the barriers associated with this reaction, significant progress has been made in developing molecular complexes that reduce N2 into its bioavailable form, NH3. This progress is driven by the dual aims of better understanding biological nitrogenases and improving upon industrial nitrogen fixation. In this review, we highlight both mechanistic understanding of nitrogen fixation that has been developed, as well as advances in yields, efficiencies, and rates that make molecular alternatives to nitrogen fixation increasingly appealing. We begin with a historical discussion of N2 functionalization chemistry that traverses a timeline of events leading up to the discovery of the first bona fide molecular catalyst system and follow with a comprehensive overview of d-block compounds that have been targeted as catalysts up to and including 2019. We end with a summary of lessons learned from this significant research effort and last offer a discussion of key remaining challenges in the field.
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Affiliation(s)
- Matthew J Chalkley
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Marcus W Drover
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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49
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Guo F, Tsoureas N, Huang G, Tong M, Mansikkamäki A, Layfield RA. Isolation of a Perfectly Linear Uranium(II) Metallocene. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201912663] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Fu‐Sheng Guo
- Department of ChemistryUniversity of Sussex Falmer, Brighton BN1 9QR UK
| | - Nikolaos Tsoureas
- Department of ChemistryUniversity of Sussex Falmer, Brighton BN1 9QR UK
| | - Guo‐Zhang Huang
- Key Laboratory of Bioinorganic and Synthetic Chemistry of the Ministry of EducationSchool of ChemistrySun Yat-Sen University Guangzhou 510275 P. R. China
| | - Ming‐Liang Tong
- Key Laboratory of Bioinorganic and Synthetic Chemistry of the Ministry of EducationSchool of ChemistrySun Yat-Sen University Guangzhou 510275 P. R. China
| | - Akseli Mansikkamäki
- Department of ChemistryNanoscience CenterUniversity of Jyväskylä P.O. Box 35 40014 Jyväskylä Finland
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50
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Guo FS, Tsoureas N, Huang GZ, Tong ML, Mansikkamäki A, Layfield RA. Isolation of a Perfectly Linear Uranium(II) Metallocene. Angew Chem Int Ed Engl 2020; 59:2299-2303. [PMID: 31710765 DOI: 10.1002/anie.201912663] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 10/21/2019] [Indexed: 11/11/2022]
Abstract
Reduction of the uranium(III) metallocene [(η5 -C5 i Pr5 )2 UI] (1) with potassium graphite produces the "second-generation" uranocene [(η5 -C5 i Pr5 )2 U] (2), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground-state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f3 6d1 . Appreciable covalent contributions to the metal-ligand bonds were determined from a computational study of 2, including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s-6d z 2 mixing.
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Affiliation(s)
- Fu-Sheng Guo
- Department of Chemistry, University of Sussex, Falmer, Brighton, BN1 9QR, UK
| | - Nikolaos Tsoureas
- Department of Chemistry, University of Sussex, Falmer, Brighton, BN1 9QR, UK
| | - Guo-Zhang Huang
- Key Laboratory of Bioinorganic and Synthetic Chemistry of the Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou, 510275, P. R. China
| | - Ming-Liang Tong
- Key Laboratory of Bioinorganic and Synthetic Chemistry of the Ministry of Education, School of Chemistry, Sun Yat-Sen University, Guangzhou, 510275, P. R. China
| | - Akseli Mansikkamäki
- Department of Chemistry, Nanoscience Center, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland
| | - Richard A Layfield
- Department of Chemistry, University of Sussex, Falmer, Brighton, BN1 9QR, UK
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