1
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Liu L, Johnson SI, Appel AM, Bullock RM. Oxidation of Ammonia Catalyzed by a Molecular Iron Complex: Translating Chemical Catalysis to Mediated Electrocatalysis. Angew Chem Int Ed Engl 2024; 63:e202402635. [PMID: 38981858 DOI: 10.1002/anie.202402635] [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: 02/06/2024] [Revised: 07/08/2024] [Accepted: 07/09/2024] [Indexed: 07/11/2024]
Abstract
Ammonia is a promising candidate in the quest for sustainable, clean energy. With its capacity to serve as an energy carrier, the oxidation of ammonia opens avenues for carbon-neutral approaches to address worldwide growing energy needs. We report the catalytic chemical oxidation of ammonia by an Earth-abundant transition metal complex, trans-[LFeII(MeCN)2][PF6]2, where L is a macrocyclic ligand bearing four N-heterocyclic carbene (NHC) donors. Using triarylaminium radical cations in MeCN, up to 182 turnovers of N2 per Fe were obtained from chemical catalysis with an extremely low loading of the Fe catalyst (0.043 mM, 0.004 mol % catalyst). This chemical catalysis was successfully transitioned to mediated electrocatalysis for the oxidation of ammonia. Molecular electrocatalysis by the Fe catalyst and the mediator (p-MeOC6H4)3N exhibited a catalytic half-wave potential (Ecat/2) of 0.18 V vs [Cp2Fe]+/0 in MeCN, and achieved 9.3 turnovers of N2 at an applied potential of 0.20 V vs [Cp2Fe]+/0 at -20 °C in controlled-potential electrolysis, with a Faradaic efficiency of 75 %. Based on computational results, the catalyst undergoes sequential oxidation and deprotonation steps to form [LFeIV(NH2)2]2+, and thereafter bimetallic coupling to form an N-N bond.
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Affiliation(s)
- Liang Liu
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA
- Current address: College of Chemistry, Central China Normal University, Wuhan, Hubei, 430079, P. R. China
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA
| | - Aaron M Appel
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington, 99352, USA
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2
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Feng S, Chen J, Wang R, Li H, Xie J, Guo Z, Lau TC, Liu Y. Dual Pathways in Catalytic Ammonia Oxidation by a Ruthenium Complex Bearing a Tetradentate Bipyridine-Bipyrazole Ligand: Isolation of a Diruthenium Intermediate with a μ-Hexazene Derivative. J Am Chem Soc 2024; 146:21490-21495. [PMID: 39054650 DOI: 10.1021/jacs.4c04326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2024]
Abstract
We report herein chemical and electrochemical ammonia oxidation (AO) catalyzed by a Ru complex, [RuII(H2L)(pic)2]2+ [1, H2L = 6,6'-di(1H-pyrazol-3-yl)-2,2'-bipyridine, pic = 4-picoline], where H2L is a tetradentate ligand with a bipyridyl unit connected to two pyrazoles. 1 functions as an efficient electrocatalyst for the oxidation of NH3 to N2, with a low overpotential of 0.51 V vs Fc+/0 and a Faradaic efficiency of 96%. 1 also undergoes catalytic chemical AO using (4-BrPh)3N•+ as an oxidant, with a turnover number for N2 reaching 41. A novel binuclear complex, [RuIII(L)(pic)2(N2)RuIII(L)(pic)2]4+ (2), was isolated and structurally characterized in the catalytic chemical AO by 1. Complex 2 possesses a zigzag dianionic μ-hexazene unit where the N2 derived from ammonia oxidation is bonded to the pyrazoles, with an NN2-NN2 bond length of 1.3091(70) Å. 2 readily releases N2 upon treating with NH3. Based on experimental and DFT studies, in chemical AO the formation of an N-N bond is proposed to occur via bimolecular coupling of a ruthenium pyrazole imido intermediate to give 2; while in electrochemical AO the N-N bond is formed by nucleophilic attack of NH3 on the intermediate.
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Affiliation(s)
- Sushan Feng
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Jing Chen
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Rui Wang
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Hui Li
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Jianhui Xie
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Zhenguo Guo
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Tai-Chu Lau
- Department of Chemistry, City University of Hong Kong, Kowloon Tong 999077 Hong Kong, P. R. China
| | - Yingying Liu
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
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3
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Trenerry MJ, Acosta M, Berry JF. Computational Analysis of Low Overpotential Ammonia Oxidation by Metal-Metal Bonded Ruthenium Catalysts, and Predictions for Related Osmium Catalysts. J Phys Chem A 2024; 128:4038-4051. [PMID: 38742806 DOI: 10.1021/acs.jpca.4c02490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
The catalyzed electrochemical oxidation of ammonia to nitrogen (AOR) is an important fuel-cell half-reaction that underpins a future nitrogen-based energy economy. Our laboratory has reported spontaneous chemical and electrochemical oxidation of ammonia to dinitrogen via reaction of ammonia with the metal-metal bonded diruthenium complex Ru2(chp)4OTf (chp- = 2-chloro-6-hydroxypyridinate, TfO- = trifluoromethanesulfonate). This complex facilitates electrocatalytic ammonia oxidation at mild applied potentials of -255 mV vs ferrocene, which is the [Ru2(chp)4(NH3)]0/+ redox potential. We now report a comprehensive computational investigation of possible mechanisms for this reaction and electronic structure analysis of key intermediates therein. We extend this analysis to proposed second-generation electrocatalysts bearing structurally similar fhp and hmp (2-fluoro-6-hydroxypyridinate and 2-hydroxy-6-methylpyridinate, respectively) equatorial ligands, and we further expand this study from Ru2 to analogous Os2 cores. Predicted M24+/5+ redox potentials, which we expect to correlate with experimental AOR overpotential, depend strongly on the identity of the metal center, and to a lesser degree on the nature of the equatorial supporting ligand. Os2 complexes are easier to oxidize than analogous Ru2 complexes by ∼640 mV, on average. In contrast to mono-Ru catalysts, which oxidize ammonia via a rate-limiting activation of the strong N-H bond, we find lowest-energy reaction pathways for Ru2 and Os2 complexes that involve direct N-N bond formation onto electrophilic intermediates having terminal amido, imido, or nitrido groups. While transition state energies for Os2 complexes are high, those for Ru2 complexes are moderate and notably lower than those for mono-Ru complexes. We attribute these lower barriers to enhanced electrophilicity of the Ru2 intermediates, which is a consequence of their metal-metal bonded structure. Os2 intermediates are found to be, surprisingly, less electrophilic, and we suggest that Os2 complexes may require access to oxidation states higher than Os25+ in order to perform AOR at reasonable reaction rates.
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Affiliation(s)
- Michael J Trenerry
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
- Department of Chemistry, University of Minnesota - Twin Cities, Minneapolis, Minnesota 55455, United States
| | - Milton Acosta
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
| | - John F Berry
- Department of Chemistry, University of Wisconsin - Madison, Madison, Wisconsin 53706, United States
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4
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Phearman AS, Bullock RM. Synthesis and Reactivity of Fe(II) Complexes Containing Cis Ammonia Ligands. Inorg Chem 2024; 63:2024-2033. [PMID: 38230973 DOI: 10.1021/acs.inorgchem.3c03757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2024]
Abstract
The development of earth-abundant transition-metal complexes for electrocatalytic ammonia oxidation is needed to facilitate a renewable energy economy. Important to this goal is a fundamental understanding of how ammonia binds to complexes as a function of ligand geometry and electronic effects. We report the synthesis and characterization of a series of Fe(II)-NH3 complexes supported by tetradentate, facially binding ligands with a combination of pyridine and N-heterocyclic carbene donors. Electronic modification of the supporting ligand led to significant shifts in the FeIII/II potential and variations in NH bond acidities. Finally, investigations of ammonia oxidation by cyclic voltammetry, controlled potential bulk electrolysis, and through addition of stoichiometric organic radicals, TEMPO and tBu3ArO• are reported. No catalytic oxidation of NH3 to N2 was observed, and 15N2 was detected only in reactions with tBu3ArO•.
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Affiliation(s)
- Alexander S Phearman
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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5
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Roithmeyer H, Sévery L, Moehl T, Spingler B, Blacque O, Fox T, Iannuzzi M, Tilley SD. Electrocatalytic Ammonia Oxidation with a Tailored Molecular Catalyst Heterogenized via Surface Host-Guest Complexation. J Am Chem Soc 2024; 146:430-436. [PMID: 38134360 DOI: 10.1021/jacs.3c09725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2023]
Abstract
Macrocyclic host molecules bound to electrode surfaces enable the complexation of catalytically active guests for molecular heterogeneous catalysis. We present a surface-anchored host-guest complex with the ability to electrochemically oxidize ammonia in both organic and aqueous solutions. With an adamantyl motif as the binding group on the backbone of the molecular catalyst [Ru(bpy-NMe2)(tpada)(Cl)](PF6) (1) (where bpy-NMe2 is 4,4'-bis(dimethylamino)-2,2'-bipyridyl and tpada is 4'-(adamantan-1-yl)-2,2':6',2″-terpyridine), high binding constants with β-cyclodextrin were observed in solution (in DMSO-d6:D2O (7:3), K11 = 492 ± 21 M-1). The strong binding affinities were also transferred to a mesoporous ITO (mITO) surface functionalized with a phosphonated derivative of β-cyclodextrin. The newly designed catalyst (1) was compared to the previously reported naphthyl-substituted catalyst [Ru(bpy-NMe2)(tpnp)(Cl)](PF6) (2) (where tpnp is 4'-(naphthalene-2-yl)-2,2':6',2″-terpyridine) for its stability during catalysis. Despite the insulating nature of the adamantyl substituent serving as the binding group, the stronger binding of this unit to the host-functionalized electrode and the resulting shorter distance between the catalytic active center and the surface led to better performance and higher stability. Both guests are able to oxidize ammonia in both organic and aqueous solutions, and the host-anchored electrode can be refunctionalized multiple times (>3) following the loss of the catalytic activity, without a reduction in performance. Guest 1 exhibits significantly higher stability in comparison to guest 2 toward basic conditions, which often constitutes a challenge for anchored molecular systems. Ammonia oxidation in water led to the selective formation of NO3- with Faradaic efficiencies of up to 100%.
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Affiliation(s)
- Helena Roithmeyer
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - Laurent Sévery
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - Thomas Moehl
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - Bernhard Spingler
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - Olivier Blacque
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - Thomas Fox
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - Marcella Iannuzzi
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | - S David Tilley
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
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6
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Beiler AM, Denisiuk A, Holub J, Sánchez-Baygual FJ, Gil-Sepulcre M, Ertem MZ, Moonshiram D, Piccioni A, Llobet A. Heterogeneous Electrochemical Ammonia Oxidation with a Ru-bda Oligomer Anchored on Graphitic Electrodes via CH-π Interactions. ACS ENERGY LETTERS 2023; 8:172-178. [PMID: 36660370 PMCID: PMC9841602 DOI: 10.1021/acsenergylett.2c02483] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 11/10/2022] [Indexed: 06/17/2023]
Abstract
Molecular catalysts can promote ammonia oxidation, providing mechanistic insights into the electrochemical N2 cycle for a carbon-free fuel economy. We report the ammonia oxidation activity of carbon anodes functionalized with the oligomer {[RuII(bda-κ-N 2 O 2)(4,4'-bpy)]10(4,4'-bpy)}, Rubda-10, where bda is [2,2'-bipyridine]-6,6'-dicarboxylate and 4,4'-bpy is 4,4'-bipyridine. Electrocatalytic studies in propylene carbonate demonstrate that the Ru-based hybrid anode used in a 3-electrode configuration transforms NH3 to N2 and H2 in a 1:3 ratio with near-unity faradaic efficiency at an applied potential of 0.1 V vs Fc+/0, reaching turnover numbers of 7500. X-ray absorption spectroscopic analysis after bulk electrolysis confirms the molecular integrity of the catalyst. Based on computational studies together with electrochemical evidence, ammonia nucleophilic attack is proposed as the primary pathway that leads to critical N-N bond formation.
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Affiliation(s)
- Anna M. Beiler
- Institute
of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), 43007Tarragona, Spain
| | - Alisa Denisiuk
- Institute
of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), 43007Tarragona, Spain
| | - Jan Holub
- Institute
of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), 43007Tarragona, Spain
| | | | - Marcos Gil-Sepulcre
- Institute
of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), 43007Tarragona, Spain
| | - Mehmed Z. Ertem
- Chemistry
Division, Energy & Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York11973-5000, United States
| | - Dooshaye Moonshiram
- Instituto
de Ciencia de Materiales de Madrid, Consejo
Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz,
3, 28049, Madrid, Spain
| | - Alberto Piccioni
- Department
of Physics and Astronomy, University of
Bologna, Viale C. Berti-Pichat 6/2, 40127Bologna, BO, Italy
| | - Antoni Llobet
- Institute
of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), 43007Tarragona, Spain
- Departament
de Química, Universitat Autònoma
de Barcelona, Cerdanyola
del Vallès, 08193Barcelona, Spain
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7
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Stephens DN, Szilagyi RK, Roehling PN, Arulsamy N, Mock MT. Catalytic Ammonia Oxidation to Dinitrogen by a Nickel Complex. Angew Chem Int Ed Engl 2023; 62:e202213462. [PMID: 36279321 DOI: 10.1002/anie.202213462] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Indexed: 11/07/2022]
Abstract
We report a nickel complex for catalytic oxidation of ammonia to dinitrogen under ambient conditions. Using the aryloxyl radical 2,4,6-tri-tert-butylphenoxyl (t Bu3 ArO⋅) as a H atom acceptor to cleave the N-H bond of a coordinated NH3 ligand up to 56 equiv of N2 per Ni center can be generated. Employing the N-oxyl radical 2,2,6,6-(tetramethylpiperidin-1-yl)oxyl (TEMPO⋅) as the H-atom acceptor, up to 15 equiv of N2 per Ni center are formed. A bridging Ni-hydrazine product identified by isotopic nitrogen (15 N) studies and supported by computational models indicates the N-N bond forming step occurs by bimetallic homocoupling of two paramagnetic [Ni]-NH2 fragments. Ni-mediated hydrazine disproportionation to N2 and NH3 completes the catalytic cycle.
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Affiliation(s)
- David N Stephens
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | - Robert K Szilagyi
- Department of Chemistry, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada
| | - Paige N Roehling
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | - Navamoney Arulsamy
- Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071, USA
| | - Michael T Mock
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
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8
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Tanabe Y, Nishibayashi Y. Recent advances in catalytic nitrogen fixation using transition metal–dinitrogen complexes under mild reaction conditions. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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9
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Ahmed ME, Raghibi Boroujeni M, Ghosh P, Greene C, Kundu S, Bertke JA, Warren TH. Electrocatalytic Ammonia Oxidation by a Low-Coordinate Copper Complex. J Am Chem Soc 2022; 144:21136-21145. [DOI: 10.1021/jacs.2c07977] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Md Estak Ahmed
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Mahdi Raghibi Boroujeni
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Pokhraj Ghosh
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Christine Greene
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Subrata Kundu
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
- School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, Kerala 695551, India
| | - Jeffery A. Bertke
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Timothy H. Warren
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
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10
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Dunn PL, Barona M, Johnson SI, Raugei S, Bullock RM. Hydrogen Atom Abstraction from an Os II(NH 3) 2 Complex Generates an Os IV(NH 2) 2 Complex: Experimental and Computational Analysis of the N-H Bond Dissociation Free Energies and Reactivity. Inorg Chem 2022; 61:15325-15334. [PMID: 36121917 DOI: 10.1021/acs.inorgchem.2c00708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Double hydrogen atom abstraction from (TMP)OsII(NH3)2 (TMP = tetramesitylporphyrin) with phenoxyl or nitroxyl radicals leads to (TMP)OsIV(NH2)2. This unusual bis(amide) complex is diamagnetic and displays an N-H resonance at 12.0 ppm in its 1H NMR spectrum. 1H-15N correlation experiments identified a 15N NMR spectroscopic resonance signal at -267 ppm. Experimental reactivity studies and density functional theory calculations support relatively weak N-H bonds of 73.3 kcal/mol for (TMP)OsII(NH3)2 and 74.2 kcal/mol for (TMP)OsIII(NH3)(NH2). Cyclic voltammetry experiments provide an estimate of the pKa of [(TMP)OsIII(NH3)2]+. In the presence of Barton's base, a current enhancement is observed at the Os(III/II) couple, consistent with an ECE event. Spectroscopic experiments confirmed (TMP)OsIV(NH2)2 as the product of bulk electrolysis. Double hydrogen atom abstraction is influenced by π donation from the amides of (TMP)OsIV(NH2)2 into the d orbitals of the Os center, favoring the formation of (TMP)OsIV(NH2)2 over N-N coupling. This π donation leads to a Jahn-Teller distortion that splits the energy levels of the dxz and dyz orbitals of Os, results in a low-spin electron configuration, and leads to minimal aminyl character on the N atoms, rendering (TMP)OsIV(NH2)2 unreactive toward amide-amide coupling.
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Affiliation(s)
- Peter L Dunn
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Melissa Barona
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Simone Raugei
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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11
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Cook BJ, Barona M, Johnson SI, Raugei S, Bullock RM. Weakening the N-H Bonds of NH 3 Ligands: Triple Hydrogen-Atom Abstraction to Form a Chromium(V) Nitride. Inorg Chem 2022; 61:11165-11172. [PMID: 35829761 DOI: 10.1021/acs.inorgchem.2c01115] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Weakening and cleaving N-H bonds is crucial for improving molecular ammonia (NH3) oxidation catalysts. We report the synthesis and H-atom-abstraction reaction of bis(ammonia)chromium porphyrin complexes Cr(TPP)(NH3)2 and Cr(TMP)(NH3)2 (TPP = 5,10,15,20-tetraphenyl-meso-porphyrin and TMP = 5,10,15,20-tetramesityl-meso-porphyrin) using bulky aryloxyl radicals. The triple H-atom-abstraction reaction results in the formation of CrV(por)(≡N), with the nitride derived from NH3, as indicated by UV-vis and IR and single-crystal structural determination of Cr(TPP)(≡N). Subsequent oxidation of this chromium(V) nitrido complex results in the formation of CrIII(por), with scission of the Cr≡N bond. Computational analysis illustrates the progression from CrII to CrV and evaluates the energetics of abstracting H atoms from CrII-NH3 to generate CrV≡N. The formation and isolation of CrV(por)(≡N) illustrates the stability of these species and the need to chemically activate the nitride ligand for atom transfer or N-N coupling reactivity.
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Affiliation(s)
- Brian J Cook
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Melissa Barona
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Simone Raugei
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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12
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Liu HY, Lant HMC, Troiano JL, Hu G, Mercado BQ, Crabtree RH, Brudvig GW. Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex. J Am Chem Soc 2022; 144:8449-8453. [PMID: 35535858 DOI: 10.1021/jacs.2c01788] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrocatalytic ammonia oxidation at room temperature and pressure allows energy-economical and environmentally friendly production of nitrites and nitrates. Few molecular catalysts, however, have been developed for this six- or eight-electron oxidation process. We now report [Cu(bipyalk)]+, a homogeneous electrocatalyst that realizes the title reaction in water at 94% Faradaic efficiency. The catalyst exhibits high selectivity against water oxidation in aqueous media, as [Cu(bipyalk)]+ is not competent for water oxidation.
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Affiliation(s)
- Han-Yu Liu
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, 810 West Campus Drive, West Haven, Connecticut 06516, United States
| | - Hannah M C Lant
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Jennifer L Troiano
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, 810 West Campus Drive, West Haven, Connecticut 06516, United States
| | - Gongfang Hu
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, 810 West Campus Drive, West Haven, Connecticut 06516, United States
| | - Brandon Q Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Robert H Crabtree
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, 810 West Campus Drive, West Haven, Connecticut 06516, United States
| | - Gary W Brudvig
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.,Energy Sciences Institute, Yale University, 810 West Campus Drive, West Haven, Connecticut 06516, United States
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