1
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Mukherjee A, Datta S, Richmond MG, Bhattacharya S. Ruthenium complexes of 1,4-diazabutadiene ligands with a cis-RuCl 2 moiety for catalytic acceptorless dehydrogenation of alcohols: DFT evidence of chemically non-innocent ligand participation. RSC Adv 2023; 13:25660-25672. [PMID: 37649575 PMCID: PMC10463240 DOI: 10.1039/d3ra04750d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Accepted: 08/07/2023] [Indexed: 09/01/2023] Open
Abstract
The acceptorless dehydrogenative coupling (ADC) of primary alcohols to esters by diazabutadiene-coordinated ruthenium compounds is reported. Treatment of cis-Ru(dmso)4Cl2 in acetone at 56 °C with different 1,4-diazabutadienes [p-XC6H4N[double bond, length as m-dash]C(H)(H)C[double bond, length as m-dash]NC6H4X-p; X = H, CH3, OCH3, and Cl; abbreviated as DAB-X], gives trans-Ru[κ2-N,N-DAB-X]2Cl2 as the kinetic product of substitution. Heating these products in o-xylene at 144 °C gives the thermodynamically favored cis-Ru[κ2-N,N-DAB-X]2Cl2 isomers. Electronic structure calculations confirm the greater stability of the cis diastereomer. The molecular structures for each pair of geometric isomers have been determined by X-ray diffraction analyses. Cyclic voltammetry experiments on the complexes show an oxidative response and a reductive response within 0.50 to 0.93 V and -0.76 to -1.24 V vs. SCE respectively. The cis-Ru[κ2-N,N-DAB-X]2Cl2 complexes function as catalyst precursors for the acceptorless dehydrogenative coupling of primary alcohols to H2 and homo- and cross-coupled esters. When 1,4-butanediol and 1,5-pentanediol are employed as substrates, lactones and hydroxyaldehydes are produced as the major dehydrogenation products, while secondary alcohols afforded ketones in excellent yields. The mechanism for the dehydrogenation of benzyl alcohol to benzyl benzoate and H2 using cis-Ru[κ2-N,N-DAB-H]2Cl2 (cis-1) as a catalyst precursor was investigated by DFT calculations. The data support a catalytic cycle that involves the four-coordinate species Ru[κ2-N,N-DAB-H][κ1-N-DAB-H](κ1-OCH2Ph) whose protonated κ1-diazabutadiene moiety functions as a chemically non-innocent ligand that facilitates a β-hydrogen elimination from the κ1-O-benzoxide ligand to give the corresponding hydride HRu[κ2-N,N-DAB-H][κ1-N-DAB-H](κ2-O,C-benzaldehyde). H2 production follows a Noyori-type elimination to give (H2)Ru[κ2-N,N-DAB-H][κ1-N-DAB-H](κ1-O-benzaldehyde) as an intermediate in the catalytic cycle.
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Affiliation(s)
- Aparajita Mukherjee
- Department of Chemistry, Inorganic Chemistry Section, Jadavpur University Kolkata 700 032 India
| | - Sayanti Datta
- Department of Chemistry, Brainware University Kolkata 700 125 India
| | | | - Samaresh Bhattacharya
- Department of Chemistry, Inorganic Chemistry Section, Jadavpur University Kolkata 700 032 India
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2
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Chacon-Teran MA, Findlater M. Redox‐active BIAN‐based Iron Complexes in Catalysis. Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202200363] [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)
| | - Michael Findlater
- University of California Merced Department of Chemistry 5200 N. Lake Road 95340 Merced UNITED STATES
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3
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Jesse KA, Anferov SW, Collins KA, Valdez-Moreira JA, Czaikowski ME, Filatov AS, Anderson JS. Direct Aerobic Generation of a Ferric Hydroperoxo Intermediate Via a Preorganized Secondary Coordination Sphere. J Am Chem Soc 2021; 143:18121-18130. [PMID: 34698493 PMCID: PMC8569801 DOI: 10.1021/jacs.1c06911] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Indexed: 01/19/2023]
Abstract
Enzymes exert control over the reactivity of metal centers with precise tuning of the secondary coordination sphere of active sites. One particularly elegant illustration of this principle is in the controlled delivery of proton and electron equivalents in order to activate abundant but kinetically inert oxidants such as O2 for oxidative chemistry. Chemists have drawn inspiration from biology in designing molecular systems where the secondary coordination sphere can shuttle protons or electrons to substrates. However, a biomimetic activation of O2 requires the transfer of both protons and electrons, and molecular systems where ancillary ligands are designed to provide both of these equivalents are comparatively rare. Here, we report the use of a dihydrazonopyrrole (DHP) ligand complexed to Fe to perform exactly such a biomimetic activation of O2. In the presence of O2, this complex directly generates a high spin Fe(III)-hydroperoxo intermediate which features a DHP• ligand radical via ligand-based transfer of an H atom. This system displays oxidative reactivity and ultimately releases hydrogen peroxide, providing insight on how secondary coordination sphere interactions influence the evolution of oxidizing intermediates in Fe-mediated aerobic oxidations.
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Affiliation(s)
- Kate A. Jesse
- Department
of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Sophie W. Anferov
- Department
of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Kelsey A. Collins
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | | | - Maia E. Czaikowski
- Department
of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Alexander S. Filatov
- Department
of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - John S. Anderson
- Department
of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
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4
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Jesse KA, Chang M, Filatov AS, Anderson JS. Iron(II) Complexes Featuring a Redox‐Active Dihydrazonopyrrole Ligand. Z Anorg Allg Chem 2021; 647:1415-1420. [DOI: 10.1002/zaac.202100097] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Kate A. Jesse
- University of Chicago Department of Chemistry 929 E 57th St. Chicago IL 60637
| | - Mu‐Chieh Chang
- National Taiwan University Department of Chemistry No. 1, Section 4, Roosevelt Rd, Da'an District Taipei City Taiwan 10
| | | | - John S. Anderson
- University of Chicago Department of Chemistry 929 E 57th St. Chicago IL 60637
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5
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Fantuzzi F, Nascimento MAC, Ginovska B, Bullock RM, Raugei S. Splitting of multiple hydrogen molecules by bioinspired diniobium metal complexes: a DFT study. Dalton Trans 2021; 50:840-849. [PMID: 33237062 DOI: 10.1039/d0dt03411h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Splitting of molecular hydrogen (H2) into bridging and terminal hydrides is a common step in transition metal chemistry. Herein, we propose a novel organometallic platform for cleavage of multiple H2 molecules, which combines metal centers capable of stabilizing multiple oxidation states, and ligands bearing positioned pendant basic groups. Using quantum chemical modeling, we show that low-valent, early transition metal diniobium(ii) complexes with diphosphine ligands featuring pendant amines can favorably uptake up to 8 hydrogen atoms, and that the energetics are favored by the formation of intramolecular dihydrogen bonds. This result suggests new possible strategies for the development of hydrogen scavenger molecules that are able to perform reversible splitting of multiple H2 molecules.
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Affiliation(s)
- Felipe Fantuzzi
- Instituto de Química, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos 149, 21941.909, Rio de Janeiro, Brazil.
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6
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Hobballah A, Lounissi S, Motei R, Elleouet C, Pétillon FY, Schollhammer P. Synthesis, Characterization and Electrochemical Reductive Properties of Complexes [Fe
2
(CO)
4
(κ
2
‐P
Ph
2
N
R
2
)(
µ
‐dithiolato)] Related to the H‐Cluster of [FeFe]‐H
2
ases. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.202000824] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ahmad Hobballah
- UMR CNRS 6521 Chimie Electrochimie Moléculaires et Chimie Analytique Université de Bretagne Occidentale UFR Sciences et Techniques 6 Avenue Victor le Gorgeu, CS 93837 29238 Brest‐Cedex 3 France
| | - Sondes Lounissi
- UMR CNRS 6521 Chimie Electrochimie Moléculaires et Chimie Analytique Université de Bretagne Occidentale UFR Sciences et Techniques 6 Avenue Victor le Gorgeu, CS 93837 29238 Brest‐Cedex 3 France
| | - Rachid Motei
- UMR CNRS 6521 Chimie Electrochimie Moléculaires et Chimie Analytique Université de Bretagne Occidentale UFR Sciences et Techniques 6 Avenue Victor le Gorgeu, CS 93837 29238 Brest‐Cedex 3 France
| | - Catherine Elleouet
- UMR CNRS 6521 Chimie Electrochimie Moléculaires et Chimie Analytique Université de Bretagne Occidentale UFR Sciences et Techniques 6 Avenue Victor le Gorgeu, CS 93837 29238 Brest‐Cedex 3 France
| | - François Y. Pétillon
- UMR CNRS 6521 Chimie Electrochimie Moléculaires et Chimie Analytique Université de Bretagne Occidentale UFR Sciences et Techniques 6 Avenue Victor le Gorgeu, CS 93837 29238 Brest‐Cedex 3 France
| | - Philippe Schollhammer
- UMR CNRS 6521 Chimie Electrochimie Moléculaires et Chimie Analytique Université de Bretagne Occidentale UFR Sciences et Techniques 6 Avenue Victor le Gorgeu, CS 93837 29238 Brest‐Cedex 3 France
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7
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Wang WH, Wang H, Yang Y, Lai X, Li Y, Wang J, Himeda Y, Bao M. Synergistic Effect of Pendant N Moieties for Proton Shuttling in the Dehydrogenation of Formic Acid Catalyzed by Biomimetic Ir III Complexes. CHEMSUSCHEM 2020; 13:5015-5022. [PMID: 32662920 DOI: 10.1002/cssc.202001190] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/12/2020] [Indexed: 06/11/2023]
Abstract
Formic acid (FA) is among the most promising hydrogen storage materials. The development of efficient catalysts for the dehydrogenation of FA via molecular-level control and precise tuning remains challenging. A series of biomimetic Ir complexes was developed for the efficient dehydrogenation of FA in an aqueous solution without base addition. A high turnover frequency of 46510 h-1 was achieved at 90 °C in 1 m FA solution with complex 1 bearing pendant pyridine. Experimental and mechanistic studies revealed that the integrated pendant pyridine and pyrazole moieties of complex 1 could act as proton relay and facilitate proton shuttling in the outer coordination sphere. This study provides a new strategy to control proton transfer accurately and a new principle for the design of efficient catalysts for FA dehydrogenation.
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Affiliation(s)
- Wan-Hui Wang
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
| | - Hong Wang
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
| | - Yajing Yang
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
| | - Xiaoling Lai
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
| | - Yang Li
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
| | - Jiasheng Wang
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
| | - Yuichiro Himeda
- National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8569, Japan
| | - Ming Bao
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, P. R. China
- School of Chemical Engineering, Dalian University of Technology, Panjin, 124221, P. R. China
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8
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Synthesis and Structure of Iron (II) Complexes of Functionalized 1,5-Diaza-3,7-Diphosphacyclooctanes. Molecules 2020; 25:molecules25173775. [PMID: 32825126 PMCID: PMC7503606 DOI: 10.3390/molecules25173775] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 11/30/2022] Open
Abstract
In order to synthesize new iron (II) complexes of 1,5-diaza-3,7-diphosphacyclooctanes with a wider variety of the substituents on ligands heteroatoms (including functionalized ones, namely, pyridyl groups) and co-ligands, it was found that these ligands with relatively small phenyl, benzyl, and pyridin-2-yl substituents on phosphorus atoms in acetonitrile formed bis-P,P-chelate cis-complexes [L2Fe(CH3CN)2]2+ (BF4)2−, whereas P-mesityl-substituted ligand formed only monoligand P,P-complex [LFe(CH3CN)4]2+ (BF4)2−. 3,7-dibenzyl-1,5-di(1′-(R)-phenylethyl)-1,5-diaza-3,7-diphosphacyclooctane reacted with hexahydrate of iron (II) tetrafluoroborate in acetone to give an unusual bis-ligand cationic complex of the composition [L2Fe(BF4)]+ BF4−, where two fluorine atoms of the tetrafluoroborate unit occupied two pseudo-equatorial positions at roughly octahedral iron ion, according to X-ray diffraction data. 1,5-diaza-3,7-diphosphacyclooctanes replaced tetrahydrofurane and one of the carbonyl ligands of cyclopentadienyldicarbonyl(tetrahydrofuran)iron (II) tetrafluoroborate to form heteroligand complexes [CpFeL(CO)]+BF4−. The structural studies in the solid phase and in solutions showed that diazadiphosphacyclooctane ligands of all complexes adopted chair-boat conformations so that their nitrogen atoms were in close proximity to the central iron ion. The redox properties of the obtained complexes were performed by the cyclic voltammetry method.
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9
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Budnikova YH, Khrizanforova VV. Synthetic models of hydrogenases based on framework structures containing coordinating P, N-atoms as hydrogen energy electrocatalysts – from molecules to materials. PURE APPL CHEM 2020. [DOI: 10.1515/pac-2019-1207] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Nowadays, hydrogen has become not only an extremely important chemical product but also a promising clean energy carrier for replacing fossil fuels. Production of molecular H2 through electrochemical hydrogen evolution reactions is crucial for the development of clean-energy technologies. The development of economically viable and efficient H2 production/oxidation catalysts is a key step in the creation of H2-based renewable energy infrastructure. Intrinsic limitations of both natural enzymes and synthetic materials have led researchers to explore enzyme-induced catalysts to realize a high current density at a low overpotential. In recent times, highly active widespread numerous electrocatalysts, both homogeneous or heterogeneous (immobilized on the electrode), such as transition metal complexes, heteroatom- or metal-doped nanocarbons, metal-organic frameworks, and other metal derivatives (calix [4] resorcinols, pectates, etc.), which are, to one extent or another, structural or functional analogs of hydrogenases, have been extensively studied as alternatives for Pt-based catalysts, demonstrating prospects for the development of a “hydrogen economy”. This mini-review generalizes some achievements in the field of development of new electrocatalysts for H2 production/oxidation and their application for fuel cells, mainly focuses on the consideration of the catalytic activity of M[P2N2]2
2+ (M = Ni, Fe) complexes and other nickel structures which have been recently obtained.
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Affiliation(s)
- Yulia H. Budnikova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences , 8, E.Arbuzov str. , Kazan, 420088 , Russian Federation
| | - Vera V. Khrizanforova
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences , 8, E.Arbuzov str. , Kazan, 420088 , Russian Federation
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences , Kazan , Russian Federation
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10
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Chambers GM, Johnson SI, Raugei S, Bullock RM. Anion control of tautomeric equilibria: Fe-H vs. N-H influenced by NH···F hydrogen bonding. Chem Sci 2019; 10:1410-1418. [PMID: 30842818 PMCID: PMC6369578 DOI: 10.1039/c8sc04239j] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 10/04/2018] [Indexed: 12/21/2022] Open
Abstract
Addition of excess BF4– to the iron hydride [Fe(PEtNMePEt)(CO)3H]+[B(C6F5)4]– leads to the NH tautomer, due to NH···F hydrogen bonding.
Counterions can play an active role in chemical reactivity, modulating reaction pathways, energetics and selectivity. We investigated the tautomeric equilibrium resulting from protonation of Fe(PEtNMePEt)(CO)3 (PEtNMePEt = (Et2PCH2)2NMe) at Fe or N. Protonation of Fe(PEtNMePEt)(CO)3 by [(Et2O)2H]+[B(C6F5)4]– occurs at the metal to give the iron hydride [Fe(PEtNMePEt)(CO)3H]+[B(C6F5)4]–. In contrast, treatment with HBF4·OEt2 gives protonation at the iron and at the pendant amine. Both the FeH and NH tautomers were characterized by single crystal X-ray diffraction. Addition of excess BF4– to the equilibrium mixture leads to the NH tautomer being exclusively observed, due to NH···F hydrogen bonding. A quantum chemical analysis of the bonding properties of these systems provided a quantification of hydrogen bonding of the NH to BF4– and to OTf–. Treatment of Fe(PEtNMePEt)(CO)3 with excess HOTf gives a dicationic complex where both the iron and nitrogen are protonated. Isomerization of the dicationic complex was studied by NOESY NMR spectroscopy.
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Affiliation(s)
- Geoffrey M Chambers
- Center for Molecular Electrocatalysis , Pacific Northwest National Laboratory , Richland , Washington 99352 , USA .
| | - Samantha I Johnson
- Center for Molecular Electrocatalysis , Pacific Northwest National Laboratory , Richland , Washington 99352 , USA .
| | - Simone Raugei
- 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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11
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Liao Q, Liu T, Johnson SI, Klug CM, Wiedner ES, Morris Bullock R, DuBois DL. Evaluation of attractive interactions in the second coordination sphere of iron complexes containing pendant amines. Dalton Trans 2019; 48:4867-4878. [PMID: 30882832 DOI: 10.1039/c9dt00708c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ability of different ligands to attract a pendant amine is studied in a series of iron complexes.
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Affiliation(s)
- Qian Liao
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
| | - Tianbiao Liu
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
| | - Samantha I. Johnson
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
| | - Christina M. Klug
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
| | - Eric S. Wiedner
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
| | - R. Morris Bullock
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
| | - Daniel L. DuBois
- Center for Molecular Electrocatalysis
- Pacific Northwest National Laboratory
- Richland
- USA
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12
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Thammavongsy Z, Mercer IP, Yang JY. Promoting proton coupled electron transfer in redox catalysts through molecular design. Chem Commun (Camb) 2019; 55:10342-10358. [DOI: 10.1039/c9cc05139b] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mini-review on using the secondary coordination sphere to facilitate multi-electron, multi-proton catalysis.
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Affiliation(s)
| | - Ian P. Mercer
- Department of Chemistry
- University of California
- Irvine
- USA
| | - Jenny Y. Yang
- Department of Chemistry
- University of California
- Irvine
- USA
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13
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Directing the reactivity of metal hydrides for selective CO 2 reduction. Proc Natl Acad Sci U S A 2018; 115:12686-12691. [PMID: 30463952 DOI: 10.1073/pnas.1811396115] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
A critical challenge in electrocatalytic CO2 reduction to renewable fuels is product selectivity. Desirable products of CO2 reduction require proton equivalents, but key catalytic intermediates can also be competent for direct proton reduction to H2 Understanding how to manage divergent reaction pathways at these shared intermediates is essential to achieving high selectivity. Both proton reduction to hydrogen and CO2 reduction to formate generally proceed through a metal hydride intermediate. We apply thermodynamic relationships that describe the reactivity of metal hydrides with H+ and CO2 to generate a thermodynamic product diagram, which outlines the free energy of product formation as a function of proton activity and hydricity (∆GH-), or hydride donor strength. The diagram outlines a region of metal hydricity and proton activity in which CO2 reduction is favorable and H+ reduction is suppressed. We apply our diagram to inform our selection of [Pt(dmpe)2](PF6)2 as a potential catalyst, because the corresponding hydride [HPt(dmpe)2]+ has the correct hydricity to access the region where selective CO2 reduction is possible. We validate our choice experimentally; [Pt(dmpe)2](PF6)2 is a highly selective electrocatalyst for CO2 reduction to formate (>90% Faradaic efficiency) at an overpotential of less than 100 mV in acetonitrile with no evidence of catalyst degradation after electrolysis. Our report of a selective catalyst for CO2 reduction illustrates how our thermodynamic diagrams can guide selective and efficient catalyst discovery.
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14
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15
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Khrizanforova V, Morozov V, Khrizanforov M, Lukoyanov A, Kataeva O, Fedushkin I, Budnikova Y. Iron complexes of BIANs: Redox trends and electrocatalysis of hydrogen evolution. Polyhedron 2018. [DOI: 10.1016/j.poly.2018.07.041] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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16
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Synthesis, characterization and electrocatalytic H2 production of base-containing Fe/S and Fe/Se clusters. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2018.05.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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17
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Liu J, Zhang A, Song H, Tong Q, Tung CH, Wang W. Iron(II) hydrides bearing a tetradentate PSNP ligand. CHINESE CHEM LETT 2018. [DOI: 10.1016/j.cclet.2017.09.059] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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18
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Robinson SJC, Heinekey DM. Hydride & dihydrogen complexes of earth abundant metals: structure, reactivity, and applications to catalysis. Chem Commun (Camb) 2018; 53:669-676. [PMID: 27928559 DOI: 10.1039/c6cc07529k] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent developments in the chemistry of hydride and dihydrogen complexes of iron, cobalt, and nickel are summarized. Applications in homogeneous catalysis are emphasized.
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Affiliation(s)
| | - D M Heinekey
- University of Washington, Department of Chemistry, Seattle, WA, USA
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19
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Okamura TA, Omi Y, Hirano Y, Onitsuka K. Comparative studies on the contribution of NHS hydrogen bonds in tungsten and molybdenum benzenedithiolate complexes. Dalton Trans 2018; 45:15651-15659. [PMID: 27722343 DOI: 10.1039/c6dt02250b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of monooxotungsten(iv) and dioxotungsten(vi) benzenedithiolates, (NEt4)2[WIVO(1,2-S2-3-RCONHC6H3)2] (1-W; R = CH3 (a), t-Bu (b), or CF3 (c)) and (NEt4)2[WVIO2(1,2-S2-3-RCONHC6H3)2] (2-W), were synthesized and compared with the corresponding molybdenum analogues. Single crystals of trans-1b-W were successfully obtained, and the crystal structure was determined by X-ray analysis although 1b-Mo could not be crystallized. The NHS hydrogen bonds shifted the potential of the W(iv/v) redox couple to more positive values, and the strength of the hydrogen bond and the positive shift value were strongly correlated. The hydrogen bonds in both 1-W and 2-W were weaker than those in the corresponding molybdenum analogues; however, the effect of the hydrogen bonds on the redox potential was greater in 1-W.
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Affiliation(s)
- Taka-Aki Okamura
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
| | - Yui Omi
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
| | - Yasunori Hirano
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
| | - Kiyotaka Onitsuka
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
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Yuki M, Sakata K, Nakajima K, Kikuchi S, Sekine S, Kawai H, Nishibayashi Y. Dicationic Thiolate-Bridged Diruthenium Complexes for Catalytic Oxidation of Molecular Dihydrogen. Organometallics 2017. [DOI: 10.1021/acs.organomet.7b00764] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Masahiro Yuki
- Department
of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Ken Sakata
- Faculty
of Pharmaceutical Sciences, Hoshi University, Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Kazunari Nakajima
- Department
of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Syoma Kikuchi
- Faculty
of Pharmaceutical Sciences, Hoshi University, Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Shinobu Sekine
- Fuel Cell System Engineering & Development Division, Toyota Motor Corporation, Mishuku, Susono, Shizuoka 410-1193, Japan
| | - Hiroyuki Kawai
- Fuel Cell System Engineering & Development Division, Toyota Motor Corporation, Mishuku, Susono, Shizuoka 410-1193, Japan
| | - Yoshiaki Nishibayashi
- Department
of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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21
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Arrigoni F, Bertini L, De Gioia L, Cingolani A, Mazzoni R, Zanotti V, Zampella G. Mechanistic Insight into Electrocatalytic H 2 Production by [Fe 2(CN){μ-CN(Me) 2}(μ-CO)(CO)(Cp) 2]: Effects of Dithiolate Replacement in [FeFe] Hydrogenase Models. Inorg Chem 2017; 56:13852-13864. [PMID: 29112805 DOI: 10.1021/acs.inorgchem.7b01954] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
DFT has been used to investigate viable mechanisms of the hydrogen evolution reaction (HER) electrocatalyzed by [Fe2(CN){μ-CN(Me)2}(μ-CO)(CO)(Cp)2] (1) in AcOH. Molecular details underlying the proposed ECEC electrochemical sequence have been studied, and the key functionalities of CN- and amino-carbyne ligands have been elucidated. After the first reduction, CN- works as a relay for the first proton from AcOH to the carbyne, with this ligand serving as the main electron acceptor for both reduction steps. After the second reduction, a second protonation occurs at CN- that forms a Fe(CNH) moiety: i.e., the acidic source for the H2 generation. The hydride (formally 2e/H+), necessary to the heterocoupling with H+ is thus provided by the μ-CN(Me)2 ligand and not by Fe centers, as occurs in typical L6Fe2S2 derivatives modeling the hydrogenase active site. It is remarkable, in this regard, that CN- plays a role more subtle than that previously expected (increasing electron density at Fe atoms). In addition, the role of AcOH in shuttling protons from CN- to CN(Me)2 is highlighted. The incompetence for the HER of the related species [Fe2{μ-CN(Me)2}(μ-CO)(CO)2(Cp)2]+ (2+) has been investigated and attributed to the loss of proton responsiveness caused by CN- replacement with CO. In the context of hydrogenase mimicry, an implication of this study is that the dithiolate strap, normally present in all synthetic models, can be removed from the Fe2 core without loss of HER, but the redox and acid-base processes underlying turnover switch from a metal-based to a ligand-based chemistry. The versatile nature of the carbyne, once incorporated in the Fe2 scaffold, could be exploited to develop more active and robust catalysts for the HER.
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Affiliation(s)
- Federica Arrigoni
- Department of Biotechnology and Biosciences, University of Milan-Bicocca , Piazza della Scienza 2, 20126 Milan, Italy
| | - Luca Bertini
- Department of Biotechnology and Biosciences, University of Milan-Bicocca , Piazza della Scienza 2, 20126 Milan, Italy
| | - Luca De Gioia
- Department of Biotechnology and Biosciences, University of Milan-Bicocca , Piazza della Scienza 2, 20126 Milan, Italy
| | - Andrea Cingolani
- Department of Chimica Industriale "Toso Montanari", University of Bologna , V. le Risorgimento 4, 40136 Bologna, Italy
| | - Rita Mazzoni
- Department of Chimica Industriale "Toso Montanari", University of Bologna , V. le Risorgimento 4, 40136 Bologna, Italy
| | - Valerio Zanotti
- Department of Chimica Industriale "Toso Montanari", University of Bologna , V. le Risorgimento 4, 40136 Bologna, Italy
| | - Giuseppe Zampella
- Department of Biotechnology and Biosciences, University of Milan-Bicocca , Piazza della Scienza 2, 20126 Milan, Italy
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22
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Bullock RM, Chambers GM. Frustration across the periodic table: heterolytic cleavage of dihydrogen by metal complexes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2017; 375:20170002. [PMID: 28739961 PMCID: PMC5540836 DOI: 10.1098/rsta.2017.0002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/12/2017] [Indexed: 06/07/2023]
Abstract
This perspective examines frustrated Lewis pairs (FLPs) in the context of heterolytic cleavage of H2 by transition metal complexes, with an emphasis on molecular complexes bearing an intramolecular Lewis base. FLPs have traditionally been associated with main group compounds, yet many reactions of transition metal complexes support a broader classification of FLPs that includes certain types of transition metal complexes with reactivity resembling main group-based FLPs. This article surveys transition metal complexes that heterolytically cleave H2, which vary in the degree that the Lewis pairs within these systems interact. Many of the examples include complexes bearing a pendant amine functioning as the base with the metal functioning as the hydride acceptor. Consideration of transition metal compounds in the context of FLPs can inspire new innovations and improvements in transition metal catalysis.This article is part of the themed issue 'Frustrated Lewis pair chemistry'.
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Affiliation(s)
- R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, PO Box 999, K2-12, Richland, WA 99352, USA
| | - Geoffrey M Chambers
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, PO Box 999, K2-12, Richland, WA 99352, USA
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23
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Zhang S, Appel AM, Bullock RM. Reversible Heterolytic Cleavage of the H–H Bond by Molybdenum Complexes: Controlling the Dynamics of Exchange Between Proton and Hydride. J Am Chem Soc 2017; 139:7376-7387. [DOI: 10.1021/jacs.7b03053] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Shaoguang Zhang
- Pacific Northwest National Laboratory, P.O. Box 999, K2-12, Richland, Washington 99352, United States
| | - Aaron M. Appel
- Pacific Northwest National Laboratory, P.O. Box 999, K2-12, Richland, Washington 99352, United States
| | - R. Morris Bullock
- Pacific Northwest National Laboratory, P.O. Box 999, K2-12, Richland, Washington 99352, United States
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24
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Yuki M, Sakata K, Kikuchi S, Kawai H, Takahashi T, Ando M, Nakajima K, Nishibayashi Y. Catalytic Activity of Thiolate-Bridged Diruthenium Complexes Bearing Pendent Ether Moieties in the Oxidation of Molecular Dihydrogen. Chemistry 2017; 23:1007-1012. [PMID: 27779798 DOI: 10.1002/chem.201604974] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Indexed: 11/06/2022]
Abstract
Thiolate-bridged diruthenium complexes bearing pendent ethers have been found to work as effective catalysts toward the oxidation of molecular dihydrogen into protons and electrons in water. The pendent ether moiety in the complex plays an important role to facilitate the proton transfer between the metal center and the external proton acceptor.
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Affiliation(s)
- Masahiro Yuki
- Department of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Ken Sakata
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara, Shinagawa-ku, Tokyo, 142-8501, Japan
| | - Shoma Kikuchi
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara, Shinagawa-ku, Tokyo, 142-8501, Japan
| | - Hiroyuki Kawai
- Fuel Cell System Development Center, Toyota Motor Corporation, Mishuku, Susono, Shizuoka, 410-1193, Japan
| | - Tsuyoshi Takahashi
- Fuel Cell System Development Center, Toyota Motor Corporation, Mishuku, Susono, Shizuoka, 410-1193, Japan
| | - Masaki Ando
- Fuel Cell System Development Center, Toyota Motor Corporation, Mishuku, Susono, Shizuoka, 410-1193, Japan
| | - Kazunari Nakajima
- Department of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Yoshiaki Nishibayashi
- Department of Systems Innovation, School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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25
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Huang TH, Yang H, Zhu SL, Zhao B, Yang Y. Synthesis, structures and fluorescent properties of metal complexes based on polyphosphine ligands. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2016.07.076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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26
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Belkova NV, Epstein LM, Filippov OA, Shubina ES. Hydrogen and Dihydrogen Bonds in the Reactions of Metal Hydrides. Chem Rev 2016; 116:8545-87. [PMID: 27285818 DOI: 10.1021/acs.chemrev.6b00091] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The dihydrogen bond-an interaction between a transition-metal or main-group hydride (M-H) and a protic hydrogen moiety (H-X)-is arguably the most intriguing type of hydrogen bond. It was discovered in the mid-1990s and has been intensively explored since then. Herein, we collate up-to-date experimental and computational studies of the structural, energetic, and spectroscopic parameters and natures of dihydrogen-bonded complexes of the form M-H···H-X, as such species are now known for a wide variety of hydrido compounds. Being a weak interaction, dihydrogen bonding entails the lengthening of the participating bonds as well as their polarization (repolarization) as a result of electron density redistribution. Thus, the formation of a dihydrogen bond allows for the activation of both the MH and XH bonds in one step, facilitating proton transfer and preparing these bonds for further transformations. The implications of dihydrogen bonding in different stoichiometric and catalytic reactions, such as hydrogen exchange, alcoholysis and aminolysis, hydrogen evolution, hydrogenation, and dehydrogenation, are discussed.
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Affiliation(s)
- Natalia V Belkova
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , Vavilov Street 28, 119991 Moscow, Russia
| | - Lina M Epstein
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , Vavilov Street 28, 119991 Moscow, Russia
| | - Oleg A Filippov
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , Vavilov Street 28, 119991 Moscow, Russia
| | - Elena S Shubina
- A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences , Vavilov Street 28, 119991 Moscow, Russia
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27
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Chen X, Yang X. Bioinspired Design and Computational Prediction of Iron Complexes with Pendant Amines for the Production of Methanol from CO2 and H2. J Phys Chem Lett 2016; 7:1035-1041. [PMID: 26937854 DOI: 10.1021/acs.jpclett.6b00161] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Inspired by the active site structure of [FeFe]-hydrogenase, we built a series of iron dicarbonyl diphosphine complexes with pendant amines and predicted their potentials to catalyze the hydrogenation of CO2 to methanol using density functional theory. Among the proposed iron complexes, [(P(tBu)2N(tBu)2H)FeH(CO)2(COOH)](+) (5COOH) is the most active one with a total free energy barrier of 23.7 kcal/mol. Such a low barrier indicates that 5COOH is a very promising low-cost catalyst for high-efficiency conversion of CO2 and H2 to methanol under mild conditions. For comparison, we also examined Bullock's Cp iron diphosphine complex with pendant amines, [(P(tBu)2N(tBu)2H)FeHCp(C5F4N)](+) (5Cp-C5F4N), as a catalyst for hydrogenation of CO2 to methanol and obtained a total free energy barrier of 27.6 kcal/mol, which indicates that 5Cp-C5F4N could also catalyze the conversion of CO2 and H2 to methanol but has a much lower efficiency than our newly designed iron complexes.
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Affiliation(s)
- Xiangyang Chen
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, People's Repubic of China
- University of Chinese Academy of Sciences , Beijing 100049, People's Repubic of China
| | - Xinzheng Yang
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, People's Repubic of China
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28
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Affiliation(s)
- Robert H. Crabtree
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States
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29
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Abstract
Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.
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Affiliation(s)
- Robert H Morris
- Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
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30
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Bullock RM, Helm ML. Molecular electrocatalysts for oxidation of hydrogen using earth-abundant metals: shoving protons around with proton relays. Acc Chem Res 2015; 48:2017-26. [PMID: 26079983 DOI: 10.1021/acs.accounts.5b00069] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Sustainable, carbon-neutral energy is needed to supplant the worldwide reliance on fossil fuels in order to address the persistent problem of increasing emissions of CO2. Solar and wind energy are intermittent, highlighting the need to develop energy storage on a huge scale. Electrocatalysts provide a way to convert between electrical energy generated by renewable energy sources and chemical energy in the form of chemical bonds. Oxidation of hydrogen to give two electrons and two protons is carried out in fuel cells, but the typical catalyst is platinum, a precious metal of low earth abundance and high cost. In nature, hydrogenases based on iron or iron/nickel reversibly oxidize hydrogen with remarkable efficiencies and rates. Functional models of these enzymes have been synthesized with the goal of achieving electrocatalytic H2 oxidation using inexpensive, earth-abundant metals along with a key feature identified in the [FeFe]-hydrogenase: an amine base positioned near the metal. The diphosphine ligands P(R)2N(R')2 (1,5-diaza-3,7-diphosphacyclooctane with alkyl or aryl groups on the P and N atoms) are used as ligands in Ni, Fe, and Mn complexes. The pendant amines facilitate binding and heterolytic cleavage of H2, placing the hydride on the metal and the proton on the amine. The pendant amines also serve as proton relays, accelerating intramolecular and intermolecular proton transfers. Electrochemical oxidations and deprotonations by an exogeneous amine base lead to catalytic cycles for oxidation of H2 (1 atm) at room temperature for catalysts derived from [Ni(P(Cy)2N(R')2)2](2+), Cp(C6F5)Fe(P(tBu)2N(Bn)2)H, and MnH(P(Ph)2N(Bn)2)(bppm)(CO) [bppm = (PAr(F)2)2CH2]. In the oxidation of H2 catalyzed by [Ni(P(Cy)2N(R')2)2](2+), the initial product observed experimentally is a Ni(0) complex in which two of the pendant amines are protonated. Two different pathways can occur from this intermediate; deprotonation followed by oxidation occurs with a lower overpotential than the alternate pathway involving oxidation followed by deprotonation. The Mn cation [Mn(P(Ph)2N(Bn)2)(bppm)(CO)](+) mediates the rapid (>10(4) s(-1) at -95 °C), reversible heterolytic cleavage of H2. Obtaining the optimal benefit of pendant amines incorporated into the ligand requires that the pendant amine be properly positioned to interact with a M-H or M(H2) bond. In addition, ligands are ideally selected such that the hydride-acceptor ability of the metal and the basicity of a pendant are tuned to give low barriers for heterolytic cleavage of the H-H bond and subsequent proton transfer reactions. Using these principles allows the rational design of electrocatalysts for H2 oxidation using earth-abundant metals.
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Affiliation(s)
- R. Morris Bullock
- Center
for Molecular Electrocatalysis,
Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, K2-12, Richland, Washington 99352, United States
| | - Monte L. Helm
- Center
for Molecular Electrocatalysis,
Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, K2-12, Richland, Washington 99352, United States
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