1
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Oloyede UN, Flowers RA. Coordination-induced bond weakening and small molecule activation by low-valent titanium complexes. Dalton Trans 2024; 53:2413-2441. [PMID: 38224159 DOI: 10.1039/d3dt03454b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
Bond activation of small molecules through coordination to low valent metal complexes in M⋯X-H type interactions (where X = O, N, B, Si, etc.) leads to the formation of unusually weak X-H bonds and provides a powerful approach for the synthesis of target compounds under very mild conditions. Coordination of small molecules like water, amides, silanes, boranes, and dinitrogen to Ti(III) or Ti(II) complexes results in the synergetic redistribution of electrons between the metal orbitals and the ligand orbitals which weakens and enables the facile cleavage of the X-H or N-N bonds of the ligands. This review presents an overview of coordination-induced bond activation of small molecules by low valent titanium complexes. In particular, the applications of low valent titanium-induced bond weakening in nitrogen fixation are presented. The review concludes with potential future directions for work in this area including low-valent Ti-based PCET systems, photocatalytic nitrogen reduction, and approaches to tailoring complexes for optimal bond activation.
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Affiliation(s)
| | - Robert A Flowers
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
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2
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Kim S, Kim J, Zhong H, Panetti GB, Chirik PJ. Catalytic N–H Bond Formation Promoted by a Ruthenium Hydride Complex Bearing a Redox-Active Pyrimidine-Imine Ligand. J Am Chem Soc 2022; 144:20661-20671. [DOI: 10.1021/jacs.2c07800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Sangmin Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Junho Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Hongyu Zhong
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Grace B. Panetti
- 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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3
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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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4
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Léonard NG, Chantarojsiri T, Ziller JW, Yang JY. Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes. J Am Chem Soc 2022; 144:1503-1508. [PMID: 35041788 PMCID: PMC9118977 DOI: 10.1021/jacs.1c09583] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. Similar fields can be generated in molecular systems using charged functionalities. Manganese(V) salen nitrido complexes (salen = N,N'-ethylenebis(salicylideneaminato)) appended with a crown ether unit containing Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to determine the effect of charge on pKa, E1/2, and the net bond dissociation free energy (BDFE) of N-H bonds. The series, which includes the manganese(V) salen nitrido without an appended crown, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were used with the Mn(VI/V) reduction potentials to calculate the N-H BDFEs of the imidos in acetonitrile. Despite a span of >700 mV and >9 pKa units across the series, the hydrogen atom BDFE only spans ∼6 kcal/mol (between 73 and 79 kcal/mol). These results suggest that the incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa values while minimally affecting the BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer pathways.
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Affiliation(s)
- Nadia G Léonard
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Teera Chantarojsiri
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
| | - Joseph W Ziller
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Jenny Y Yang
- Department of Chemistry, University of California, Irvine, California 92697, United States
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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5
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Ali H, Masar M, Guler AC, Urbanek M, Machovsky M, Kuritka I. Heterojunction-based photocatalytic nitrogen fixation: principles and current progress. NANOSCALE ADVANCES 2021; 3:6358-6372. [PMID: 36133492 PMCID: PMC9417957 DOI: 10.1039/d1na00565k] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 09/16/2021] [Indexed: 06/15/2023]
Abstract
Nitrogen fixation is considered one of the grand challenges of the 21st century for achieving the ultimate vision of a green and sustainable future. It is crucial to develop and design sustainable nitrogen fixation techniques with minimal environmental impact as an alternative to the energy-cost intensive Haber-Bosch process. Heterojunction-based photocatalysis has recently emerged as a viable solution for the various environmental and energy issues, including nitrogen fixation. The primary advantages of heterojunction photocatalysts are spatially separated photogenerated charge carriers while retaining high oxidation and reduction potentials of the individual components, enabling visible light-harvesting. This review summarises the fundamental principles of photocatalytic heterostructures, the reaction mechanism of the nitrogen reduction reaction, ammonia detection methods, and the current progress of heterostructured photocatalysts for nitrogen fixation. Finally, future challenges and prospects are briefly discussed for the emerging field of heterostructured photocatalytic nitrogen fixation.
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Affiliation(s)
- Hassan Ali
- Centre of Polymer Systems, Tomas Bata University in Zlin Tr. T. Bati 5678 76001 Zlin Czech Republic
| | - Milan Masar
- Centre of Polymer Systems, Tomas Bata University in Zlin Tr. T. Bati 5678 76001 Zlin Czech Republic
| | - Ali Can Guler
- Centre of Polymer Systems, Tomas Bata University in Zlin Tr. T. Bati 5678 76001 Zlin Czech Republic
| | - Michal Urbanek
- Centre of Polymer Systems, Tomas Bata University in Zlin Tr. T. Bati 5678 76001 Zlin Czech Republic
| | - Michal Machovsky
- Centre of Polymer Systems, Tomas Bata University in Zlin Tr. T. Bati 5678 76001 Zlin Czech Republic
| | - Ivo Kuritka
- Centre of Polymer Systems, Tomas Bata University in Zlin Tr. T. Bati 5678 76001 Zlin Czech Republic
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6
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Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen. Nat Chem 2021; 13:969-976. [PMID: 34253889 DOI: 10.1038/s41557-021-00732-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 05/13/2021] [Indexed: 02/08/2023]
Abstract
The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element-hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element-hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol-1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry.
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7
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Gordon JB, McGale JP, Siegler MA, Goldberg DP. Proton-Coupled Electron-Transfer Reactivity Controls Iron versus Sulfur Oxidation in Nonheme Iron-Thiolate Complexes. Inorg Chem 2021; 60:6255-6265. [PMID: 33872005 DOI: 10.1021/acs.inorgchem.0c03779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of the five-coordinate FeII(N4S) complexes, [FeII(iPr3TACN)(abtX)](OTf) (abt = aminobenzenethiolate, X = H, CF3), with a one-electron oxidant and an appropriate base leads to net H atom loss, generating new FeIII(iminobenzenethiolate) complexes that were characterized by single-crystal X-ray diffraction (XRD), as well as UV-vis, EPR, and Mössbauer spectroscopies. The spectroscopic data indicate that the iminobenzenethiolate complexes have S = 3/2 ground states. In the absence of a base, oxidation of the FeII(abt) complexes leads to disulfide formation instead of oxidation at the metal center. Bracketing studies with separated proton-coupled electron-transfer (PCET) reagents show that the FeII(aminobenzenethiolate) and FeIII(iminobenzenethiolate) forms are readily interconvertible by H+/e- transfer and provide a measure of the bond dissociation free energy (BDFE) for the coordinated N-H bond between 64 and 69 kcal mol-1. This work shows that coordination to the iron center causes a dramatic weakening of the N-H bond and that Fe- versus S-oxidation in a nonheme iron complex can be controlled by the protonation state of an ancillary amino donor.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Jeremy P McGale
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Maxime A Siegler
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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8
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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: 64] [Impact Index Per Article: 21.3] [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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9
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Agarwal RG, Kim HJ, Mayer JM. Nanoparticle O-H Bond Dissociation Free Energies from Equilibrium Measurements of Cerium Oxide Colloids. J Am Chem Soc 2021; 143:2896-2907. [PMID: 33565871 DOI: 10.1021/jacs.0c12799] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A novel equilibrium strategy for measuring the hydrogen atom affinity of colloidal metal oxide nanoparticles is presented. Reactions between oleate-capped cerium oxide nanoparticle colloids (nanoceria) and organic proton-coupled electron transfer (PCET) reagents are used as a model system. Nanoceria redox changes, or hydrogen loadings, and overall reaction stoichiometries were followed by both 1H NMR and X-ray absorption near-edge spectroscopies. These investigations revealed that, in many cases, reactions between nanoceria and PCET reagents reach equilibrium states with good mass balance. Each equilibrium state is a direct measure of the bond strength, or bond dissociation free energy (BDFE), between nanoceria and hydrogen. Further studies, including those with larger nanoceria, indicated that the relevant bond is a surface O-H. Thus, we have measured surface O-H BDFEs for nanoceria-the first experimental BDFEs for any nanoscale metal oxide. Remarkably, the measured CeO-H BDFEs span 13 kcal mol-1 (0.56 eV) with changes in the average redox state of the nanoceria colloid. Possible chemical models for this strong dependence are discussed. We propose that the tunability of ceria BDFEs may be important in explaining its effectiveness in catalysis. More generally, metal oxide BDFEs have been used as predictors of catalyst efficacy that, traditionally, have only been accessible by computational methods. These results provide important experimental benchmarks for metal oxide BDFEs and demonstrate that the concepts of molecular bond strength thermochemistry can be applied to nanoscale materials.
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Affiliation(s)
- Rishi G Agarwal
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Hyun-Jo Kim
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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10
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Margulieux GW, Kim S, Chirik PJ. Determination of the N-H Bond Dissociation Free Energy in a Pyridine(diimine)molybdenum Complex Prepared by Proton-Coupled Electron Transfer. Inorg Chem 2020; 59:15394-15401. [PMID: 33016073 DOI: 10.1021/acs.inorgchem.0c02382] [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
The pyridine(diimine)molybdenum bis(imido) complex (iPrPDI)Mo(═NTol)2 (Tol = 4-methylphenyl) was synthesized by the addition of 2 equiv of 4-methylphenylazide to the corresponding molybdenum benzene derivative, (iPrPDI)Mo(η6-C6H6) [iPrPDI = 2,6-(2,6-iPr2C6H3N═CMe)2C5H3N]. Protonation of (iPrPDI)Mo(═NTol)2 with 2,6-lutinidum triflate yielded a cationic molybdenum amido complex, [(iPrPDI)Mo(NHTol)(═NTol)][OTf], which was further transformed into the neutral molybdenum amido (iPrPDI)Mo(NHTol)(═NTol) by reduction with zinc powder. A series of spectroscopic, synthetic, and pKa determination studies along with electrochemical measurements by the protonation-reduction pathway were used to establish an N-H bond dissociation free energy (BDFE) between 65 and 69 kcal/mol for the molybdenum imido-amido compound, (iPrPDI)Mo(NHTol)(═NTol). Full-molecule density functional theory studies provided a computed value of 61 kcal/mol. By contrast, reduction of (iPrPDI)Mo(═NTol)2 with KC8 afforded the corresponding anionic molybdenum complex K[(iPrPDI)Mo(═NTol)2], which has a potassium cation intercalated with the pyridine and tolyl groups. Protonation of K[(iPrPDI)Mo(═NTol)2] with the weak amidinium acid [TBD(H)][BArF24] (TBD = triazabicyclodecene; BArF24 = B[3,5-(CF3)2C6H3]4) also produced the neutral molybdenum amido complex (iPrPDI)Mo(NHTol)(═NTol). Measurement of the pKa and oxidation potential of K[(iPrPDI)Mo(═NTol)2] provided a range of 69-73 kcal/mol for the N-H BDFE of (iPrPDI)Mo(NHTol)(═NTol), in good agreement with the protonation-reduction route and completing the square scheme. The similar pKa and redox potentials obtained from each pathway demonstrate that both sequences are energetically feasible for proton-coupled electron-transfer (PCET) events. This study on the determination of N-H BDFE of the molybdenum amido complex renders fundamental insight into the N2 reduction cycle by PCET.
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Affiliation(s)
- Grant W Margulieux
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Sangmin Kim
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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11
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Barriopedro P, Caballo J, Mena M, Pérez-Redondo A, Yélamos C. Successive Protonation and Methylation of Bridging Imido and Nitrido Ligands at Titanium Complexes. Inorg Chem 2020; 59:7631-7643. [PMID: 32396009 DOI: 10.1021/acs.inorgchem.0c00550] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reactions of nitrido complexes [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] (1) and [{Ti(η5-C5Me5)}4(μ3-N)4] (2) with electrophilic reagents ROTf (R = H, Me; OTf = OSO2CF3) in different molar ratios have allowed the structural characterization of a series of titanium intermediates en route to the formation of the ammonium salts [NR4]OTf and [NR4][Ti(η5-C5Me5)(OTf)4]. The treatment of the trinuclear imido-nitrido complex 1 with 5.5 equiv of triflic acid in toluene at room temperature led to the dinuclear complex [Ti2(η5-C5Me5)2(μ-N)(NH3)(μ-O2SOCF3)2(OTf)] (3) and [NH4]OTf. Compound 3, along with the ammonium salts [NMe4]OTf and [NMe4][Ti(η5-C5Me5)(OTf)4] (5), was also obtained in the reaction of 1 with 8 equiv of methyl triflate in toluene at 100 °C. The trinuclear complex [Ti3(η5-C5Me5)3(μ-N)(μ-NH)2(μ-O2SOCF3)(OTf)] (4), an intermediate in the formation of 3, was isolated in the treatment of 1 with 4 equiv of MeOTf, although compound 4 was prepared in better yield by treatment of 1 with Me3SiOTf (2 equiv). Addition of a large excess of MeOTf or HOTf reagents to solutions of 3 resulted in the clean formation of ammonium salts [NR4][Ti(η5-C5Me5)(OTf)4] (R = Me (5), H (6)). Treatment of the tetranuclear nitrido complex [{Ti(η5-C5Me5)}4(μ3-N)4] (2) with 1 equiv of ROTf in toluene afforded the precipitation of the ionic compounds [{Ti(η5-C5Me5)}4(μ3-N)3(μ3-NR)][OTf] (R = H (8), Me (9)), while a large excess of HOTf led to the formation of [{Ti(η5-C5Me5)}4(μ3-N)3(μ3-NH)][Ti(η5-C5Me5)(OTf)4(NH3)] (10) by rupture of a fraction of tetranuclear molecules. Complex 2 reacted with 1 equiv of [M(η5-C5H5)(CO)3H] (M = Mo, Cr) via hydrogenation of one nitrido ligand to give the molecular derivative [{Ti(η5-C5Me5)}4(μ3-N)3(μ3-NH)] (11) and [{M(η5-C5H5)(CO)3}2], while a second 1 equiv of [M(η5-C5H5)(CO)3H] produced the ionic compounds [{Ti(η5-C5Me5)}4(μ3-N)2(μ3-NH)2][M(η5-C5H5)(CO)3] (M = Mo (12), Cr (13)) by protonation of another nitrido group. The X-ray crystal structures of 3-5, 9, 10, and 13 were determined.
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Affiliation(s)
- Paula Barriopedro
- Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain
| | - Jorge Caballo
- Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain
| | - Miguel Mena
- Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain.,Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain
| | - Adrián Pérez-Redondo
- Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain.,Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain
| | - Carlos Yélamos
- Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain.,Instituto de Investigación Química "Andrés M. del Río" (IQAR), Universidad de Alcalá, 28805 Alcalá de Henares, Madrid, Spain
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12
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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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13
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Kim S, Zhong H, Park Y, Loose F, Chirik PJ. Catalytic Hydrogenation of a Manganese(V) Nitride to Ammonia. J Am Chem Soc 2020; 142:9518-9524. [PMID: 32339454 DOI: 10.1021/jacs.0c03346] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The catalytic hydrogenation of a metal nitride to produce free ammonia using a rhodium hydride catalyst that promotes H2 activation and hydrogen-atom transfer is described. The phenylimine-substituted rhodium complex (η5-C5Me5)Rh(MePhI)H (MePhI = N-methyl-1-phenylethan-1-imine) exhibited higher thermal stability compared to the previously reported (η5-C5Me5)Rh(ppy)H (ppy = 2-phenylpyridine). DFT calculations established that the two rhodium complexes have comparable Rh-H bond dissociation free energies of 51.8 kcal mol-1 for (η5-C5Me5)Rh(MePhI)H and 51.1 kcal mol-1 for (η5-C5Me5)Rh(ppy)H. In the presence of 10 mol% of the phenylimine rhodium precatalyst and 4 atm of H2 in THF, the manganese nitride (tBuSalen)Mn≡N underwent hydrogenation to liberate free ammonia with up to 6 total turnovers of NH3 or 18 turnovers of H• transfer. The phenylpyridine analogue proved inactive for ammonia synthesis under identical conditions owing to competing deleterious hydride transfer chemistry. Subsequent studies showed that the use of a non-polar solvent such as benzene suppressed formation of the cationic rhodium product resulting from the hydride transfer and enabled catalytic ammonia synthesis by proton-coupled electron transfer.
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Affiliation(s)
- Sangmin Kim
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
| | - Hongyu Zhong
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
| | - Yoonsu Park
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
| | - Florian Loose
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
| | - Paul J Chirik
- Department of Chemistry, Frick Laboratory, Princeton University, Princeton, New Jersey 08544, United States
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14
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Chalkley MJ, Peters JC. Relating N-H Bond Strengths to the Overpotential for Catalytic Nitrogen Fixation. Eur J Inorg Chem 2020; 2020:1353-1357. [PMID: 33071628 DOI: 10.1002/ejic.202000232] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Nitrogen (N2) fixation to produce bio-available ammonia (NH3) is essential to all life but is a challenging transformation to catalyse owing to the chemical inertness of N2. Transition metals can, however, bind N2 and activate it for functionalization. Significant opportunities remain in developing robust and efficient transition metal catalysts for the N2 reduction reaction (N2RR). One opportunity to target in catalyst design concerns the stabilization of transition metal diazenido species (M-NNH) that result from the first N2 functionalization step. Well-characterized M-NNH species remain very rare, likely a consequence of their low N-H bond dissociation free energies (BDFEs). In this essay, we discuss the relationship between the BDFEN-H of a given M-NNH species to the observed overpotential and selectivity for N2RR catalysis with that catalyst system. We note that developing strategies to either increase the N-H BDFEs of M-NNH species, or to avoid M-NNH intermediates altogether, are potential routes to improved N2RR efficiency.
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Affiliation(s)
- Matthew J Chalkley
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
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15
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Tanaka H, Hitaoka S, Umehara K, Yoshizawa K, Kuwata S. Mechanistic Study on Catalytic Disproportionation of Hydrazine by a Protic Pincer‐Type Iron Complex through Proton‐Coupled Electron Transfer. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201901135] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Hiromasa Tanaka
- School of Liberal Arts and Sciences Daido University Minami-ku Nagoya 457‐8530 Japan
| | - Seiji Hitaoka
- Institute of Materials Chemistry and Engineering Kyushu University Nishi-ku Fukuoka 819‐0395 Japan
| | - Kazuki Umehara
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2‐12‐1 E4‐1 O‐Okayama Meguro‐ku Tokyo 152‐8552 Japan
| | - Kazunari Yoshizawa
- Institute of Materials Chemistry and Engineering Kyushu University Nishi-ku Fukuoka 819‐0395 Japan
| | - Shigeki Kuwata
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2‐12‐1 E4‐1 O‐Okayama Meguro‐ku Tokyo 152‐8552 Japan
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16
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Bruch QJ, Connor GP, Chen CH, Holland PL, Mayer JM, Hasanayn F, Miller AJM. Dinitrogen Reduction to Ammonium at Rhenium Utilizing Light and Proton-Coupled Electron Transfer. J Am Chem Soc 2019; 141:20198-20208. [DOI: 10.1021/jacs.9b10031] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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
| | - Chun-Hsing Chen
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Patrick L. Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - James M. Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Faraj Hasanayn
- Department of Chemistry, American University of Beirut, Beirut 1107 2020, Lebanon
| | - 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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17
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Bhattacharya P, Heiden ZM, Chambers GM, Johnson SI, Bullock RM, Mock MT. Catalytic Ammonia Oxidation to Dinitrogen by Hydrogen Atom Abstraction. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201903221] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Papri Bhattacharya
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory P.O. Box 999 Richland WA 99352 USA
| | | | - Geoffrey M. Chambers
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory P.O. Box 999 Richland WA 99352 USA
| | - Samantha I. Johnson
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory P.O. Box 999 Richland WA 99352 USA
| | - R. Morris Bullock
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory P.O. Box 999 Richland WA 99352 USA
| | - Michael T. Mock
- Department of Chemistry and Biochemistry Montana State University Bozeman MT 59717 USA
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18
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Bhattacharya P, Heiden ZM, Chambers GM, Johnson SI, Bullock RM, Mock MT. Catalytic Ammonia Oxidation to Dinitrogen by Hydrogen Atom Abstraction. Angew Chem Int Ed Engl 2019; 58:11618-11624. [PMID: 31115120 DOI: 10.1002/anie.201903221] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/06/2019] [Indexed: 12/20/2022]
Abstract
Catalysts for the oxidation of NH3 are critical for the utilization of NH3 as a large-scale energy carrier. Molecular catalysts capable of oxidizing NH3 to N2 are rare. This report describes the use of [Cp*Ru(PtBu 2 NPh 2 )(15 NH3 )][BArF 4 ], (PtBu 2 NPh 2 =1,5-di(phenylaza)-3,7-di(tert-butylphospha)cyclooctane; ArF =3,5-(CF3 )2 C6 H3 ), to catalytically oxidize NH3 to dinitrogen under ambient conditions. The cleavage of six N-H bonds and the formation of an N≡N bond was achieved by coupling H+ and e- transfers as net hydrogen atom abstraction (HAA) steps using the 2,4,6-tri-tert-butylphenoxyl radical (t Bu3 ArO. ) as the H atom acceptor. Employing an excess of t Bu3 ArO. under 1 atm of NH3 gas at 23 °C resulted in up to ten turnovers. Nitrogen isotopic (15 N) labeling studies provide initial mechanistic information suggesting a monometallic pathway during the N⋅⋅⋅N bond-forming step in the catalytic cycle.
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Affiliation(s)
- Papri Bhattacharya
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA, 99352, USA
| | | | - Geoffrey M Chambers
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA, 99352, USA
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA, 99352, USA
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA, 99352, USA
| | - Michael T Mock
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717, USA
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19
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20
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Bezdek MJ, Chirik PJ. Pyridine(diimine) Chelate Hydrogenation in a Molybdenum Nitrido Ethylene Complex. Organometallics 2019. [DOI: 10.1021/acs.organomet.9b00095] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Máté J. Bezdek
- 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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21
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Wang D, Loose F, Chirik PJ, Knowles RR. N-H Bond Formation in a Manganese(V) Nitride Yields Ammonia by Light-Driven Proton-Coupled Electron Transfer. J Am Chem Soc 2019; 141:4795-4799. [PMID: 30803234 DOI: 10.1021/jacs.8b12957] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A method for the reduction of a manganese nitride to ammonia is reported, where light-driven proton-coupled electron transfer enables the formation of weak N-H bonds. Photoreduction of (saltBu)MnVN to ammonia and a Mn(II) complex has been accomplished using 9,10-dihydroacridine and a combination of an appropriately matched photoredox catalyst and weak Brønsted acid. Acid-reductant pairs with effective bond dissociation free energies between 35 and 46 kcal/mol exhibited high efficiencies. This light-driven method may provide a blueprint for new approaches to catalytic homogeneous ammonia synthesis under ambient conditions.
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Affiliation(s)
- Dian Wang
- 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
| | - Robert R Knowles
- Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States
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22
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Rather SR, Bezdek MJ, Koch M, Chirik PJ, Scholes GD. Ultrafast Photophysics of a Dinitrogen-Bridged Molybdenum Complex. J Am Chem Soc 2018; 140:6298-6307. [PMID: 29719149 DOI: 10.1021/jacs.8b00890] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Among the many metal-dinitrogen complexes synthesized, the end-on bridging (μ2, η1, η1-N2) coordination mode is notoriously unreactive for nitrogen fixation. This is principally due to the large activation energy for ground-state nitrogen-element bond formation and motivates exploration of the photoexcited reactivity of this coordination mode. To provide the foundation for this concept, the photophysics of a dinitrogen-bridged molybdenum complex was explored by ultrafast electronic spectroscopies. The complex absorbs light from the UV to near-IR, and the transitions are predominantly of metal-to-ligand charge transfer (MLCT) character. Five excitation wavelengths (440, 520, 610, 730, and 1150 nm) were employed to access MLCT bands, and the dynamics were probed between 430 and 1600 nm. Despite the large energy space occupied by electronic states (ca. 1.2 eV), the dynamics were independent of the excitation wavelength. In the proposed kinetic model, photoexcitation from a Mo-N═N-Mo centered ground state populates the π*-state delocalized over two terpyridine ligands. Due to a large terpyridine-terpyridine spatial separation, electronic localization occurs within 100 fs, augmented by symmetry breaking. The subsequent interplay of internal conversion and intersystem crossing (ISC) populates the lowest 3MLCT state in 2-3 ps. Decay to the ground state occurs either directly or via a thermally activated metal-centered (3MC) trap state having two time constants (10-15 ps, 23-26 ps [298 K]; 103 ps, 612 ps [77 K]). ISC between 1MLCT and 3MLCT involves migration of energized electron density from the terpyridine π* orbitals to the Mo-N═N-Mo core. Implication of the observed dynamics for the potential N-H bond forming reactivity are discussed.
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Affiliation(s)
- Shahnawaz R Rather
- Frick Chemistry Laboratory , Princeton University , Princeton , New Jersey 08544 , United States
| | - Máté J Bezdek
- Frick Chemistry Laboratory , Princeton University , Princeton , New Jersey 08544 , United States
| | - Marius Koch
- Frick Chemistry Laboratory , Princeton University , Princeton , New Jersey 08544 , United States
| | - Paul J Chirik
- Frick Chemistry Laboratory , Princeton University , Princeton , New Jersey 08544 , United States
| | - Gregory D Scholes
- Frick Chemistry Laboratory , Princeton University , Princeton , New Jersey 08544 , United States
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23
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Kendall AJ, Johnson SI, Bullock RM, Mock MT. Catalytic Silylation of N 2 and Synthesis of NH 3 and N 2H 4 by Net Hydrogen Atom Transfer Reactions Using a Chromium P 4 Macrocycle. J Am Chem Soc 2018; 140:2528-2536. [PMID: 29384664 DOI: 10.1021/jacs.7b11132] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the first discrete molecular Cr-based catalysts for the reduction of N2. This study is focused on the reactivity of the Cr-N2 complex, trans-[Cr(N2)2(PPh4NBn4)] (P4Cr(N2)2), bearing a 16-membered tetraphosphine macrocycle. The architecture of the [16]-PPh4NBn4 ligand is critical to preserve the structural integrity of the catalyst. P4Cr(N2)2 was found to mediate the reduction of N2 at room temperature and 1 atm pressure by three complementary reaction pathways: (1) Cr-catalyzed reduction of N2 to N(SiMe3)3 by Na and Me3SiCl, affording up to 34 equiv N(SiMe3)3; (2) stoichiometric reduction of N2 by protons and electrons (for example, the reaction of cobaltocene and collidinium triflate at room temperature afforded 1.9 equiv of NH3, or at -78 °C afforded a mixture of NH3 and N2H4); and (3) the first example of NH3 formation from the reaction of a terminally bound N2 ligand with a traditional H atom source, TEMPOH (2,2,6,6-tetramethylpiperidine-1-ol). We found that trans-[Cr(15N2)2(PPh4NBn4)] reacts with excess TEMPOH to afford 1.4 equiv of 15NH3. Isotopic labeling studies using TEMPOD afforded ND3 as the product of N2 reduction, confirming that the H atoms are provided by TEMPOH.
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Affiliation(s)
- Alexander J Kendall
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
| | - Michael T Mock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory , P.O. Box 999, Richland, Washington 99352, United States
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Bezdek MJ, Chirik PJ. Interconversion of Molybdenum Imido and Amido Complexes by Proton-Coupled Electron Transfer. Angew Chem Int Ed Engl 2018; 57:2224-2228. [PMID: 29319929 DOI: 10.1002/anie.201708406] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 12/16/2017] [Indexed: 11/07/2022]
Abstract
Interconversion of the molybdenum amido [(Ph Tpy)(PPh2 Me)2 Mo(NHtBuAr)][BArF24 ] (Ph Tpy=4'-Ph-2,2',6',2"-terpyridine; tBuAr=4-tert-butyl-C6 H4 ; ArF24 =(C6 H3 -3,5-(CF3 )2 )4 ) and imido [(Ph Tpy)(PPh2 Me)2 Mo(NtBuAr)][BArF24 ] complexes has been accomplished by proton-coupled electron transfer. The 2,4,6-tri-tert-butylphenoxyl radical was used as an oxidant and the non-classical ammine complex [(Ph Tpy)(PPh2 Me)2 Mo(NH3 )][BArF24 ] as the reductant. The N-H bond dissociation free energy (BDFE) of the amido N-H bond formed and cleaved in the sequence was experimentally bracketed between 45.8 and 52.3 kcal mol-1 , in agreement with a DFT-computed value of 48 kcal mol-1 . The N-H BDFE in combination with electrochemical data eliminate proton transfer as the first step in the N-H bond-forming sequence and favor initial electron transfer or concerted pathways.
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Affiliation(s)
- Máté J Bezdek
- Department of Chemistry, Princeton University, Frick Laboratory 292, Princeton, 08544, USA
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Frick Laboratory 292, Princeton, 08544, USA
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25
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Bezdek MJ, Chirik PJ. Interconversion of Molybdenum Imido and Amido Complexes by Proton‐Coupled Electron Transfer. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201708406] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Máté J. Bezdek
- Department of Chemistry Princeton University Frick Laboratory 292 Princeton 08544 USA
| | - Paul J. Chirik
- Department of Chemistry Princeton University Frick Laboratory 292 Princeton 08544 USA
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