1
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Cobb CR, Ngo RK, Dick EJ, Lynch VM, Rose MJ. Multi-phosphine-chelated iron-carbide clusters via redox-promoted ligand exchange on an inert hexa-iron-carbide carbonyl cluster, [Fe 6(μ 6-C)(μ 2-CO) 4(CO) 12] 2. Chem Sci 2024; 15:11455-11471. [PMID: 39055015 PMCID: PMC11268514 DOI: 10.1039/d4sc01370k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Accepted: 04/25/2024] [Indexed: 07/27/2024] Open
Abstract
We report the reactivity, structures and spectroscopic characterization of reactions of phosphine-based ligands (mono-, di- and tri-dentate) with iron-carbide carbonyl clusters. Historically, the archetype of this cluster class, namely [Fe6(μ6-C)(μ2-CO)4(CO)12]2-, can be prepared on a gram-scale but is resistant to simple ligand substitution reactions. This limitation has precluded the relevance of iron-carbide clusters relating to organometallics, catalysis and the nitrogenase active site cluster. Herein, we aimed to derive a simple and reliable method to accomplish CO → L (where L = phosphine or other general ligands) substitution reactions without harsh reagents or multi-step synthetic strategies. Ultimately, our goal was ligand-based chelation of an Fe n (μ n -C) core to achieve more synthetic control over multi-iron-carbide motifs relevant to the nitrogenase active site. We report that the key intermediate is the PSEPT-non-conforming cluster [Fe6(μ6-C)(CO)16] (2: 84 electrons), which can be generated in situ by the outer-sphere oxidation of [Fe6(μ6-C)(CO)16]2- (1: closo, 86 electrons) with 2 equiv. of [Fc]PF6. The reaction of 2 with excess PPh3 generates a singly substituted neutral cluster [Fe5(μ5-C)(CO)14PPh3] (4), similar to the reported reactivity of the substitutionally active cluster [Fe5(μ5-C)(CO)15] with monodentate phosphines (Cooke & Mays, 1990). In contrast, the reaction of 2 with flexible, bidentate phosphines (DPPE and DPPP) generates a wide range of unisolable products. However, the rigid bidentate phosphine bis(diphenylphosphino)benzene (bdpb) disproportionates the cluster into non-ligated Fe3-carbide anions paired with a bdpb-supported Fe(ii) cation, which co-crystallize in [Fe3(μ3-CH)(μ3-CO)(CO)9]2[Fe(MeCN)2(bdpb)2] (6). A successful reaction of 2 with the tripodal ligand Triphos generates the first multi-iron-chelated, authentic carbide cluster of the formula [Fe4(μ4-C)(κ3-Triphos)(CO)10] (9). DFT analysis of the key (oxidized) intermediate 2 suggests that its (μ6-C)Fe6 framework remains fully intact but is distorted into an axially compressed, 'ruffled' octahedron distinct from the parent closo cluster 1. Oxidation of the cluster in non-coordinating solvent allows for the isolation and crystallization of the CO-saturated, intact closo-analogue [Fe6(μ6-C)(CO)17] (3), indicating that the intact (μ6-C)Fe6 motif is retained during initial oxidation with [Fc]PF6. Overall, we demonstrate that redox modulation beneficially 'bends' Wade-Mingo's rules via the generation of electron-starved (non-PSEPT) intermediates, which are the key intermediates in promoting facile CO → L substitution reactions in iron-carbide-carbonyl clusters.
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Affiliation(s)
- Caitlyn R Cobb
- Department of Chemistry, The University of Texas at Austin Austin TX 78712 USA
| | - Ren K Ngo
- Department of Chemistry, The University of Texas at Austin Austin TX 78712 USA
| | - Emily J Dick
- Department of Chemistry, The University of Texas at Austin Austin TX 78712 USA
| | - Vincent M Lynch
- Department of Chemistry, The University of Texas at Austin Austin TX 78712 USA
| | - Michael J Rose
- Department of Chemistry, The University of Texas at Austin Austin TX 78712 USA
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2
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Trogadas P, Xu L, Coppens M. From Biomimicking to Bioinspired Design of Electrocatalysts for CO 2 Reduction to C 1 Products. Angew Chem Int Ed Engl 2024; 63:e202314446. [PMID: 37795670 PMCID: PMC10962605 DOI: 10.1002/anie.202314446] [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: 09/26/2023] [Revised: 10/03/2023] [Accepted: 10/04/2023] [Indexed: 10/06/2023]
Abstract
The electrochemical reduction of CO2 (CO2 RR) is a promising approach to maintain a carbon cycle balance and produce value-added chemicals. However, CO2 RR technology is far from mature, since the conventional CO2 RR electrocatalysts suffer from low activity (leading to currents <10 mA cm-2 in an H-cell), stability (<120 h), and selectivity. Hence, they cannot meet the requirements for commercial applications (>200 mA cm-2 , >8000 h, >90 % selectivity). Significant improvements are possible by taking inspiration from nature, considering biological organisms that efficiently catalyze the CO2 to various products. In this minireview, we present recent examples of enzyme-inspired and enzyme-mimicking CO2 RR electrocatalysts enabling the production of C1 products with high faradaic efficiency (FE). At present, these designs do not typically follow a methodical approach, but rather focus on isolated features of biological systems. To achieve disruptive change, we advocate a systematic design methodology that leverages fundamental mechanisms associated with desired properties in nature and adapts them to the context of engineering applications.
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Affiliation(s)
- Panagiotis Trogadas
- EPSRC “Frontier Engineering” Centre for Nature Inspired EngineeringDepartment of Chemical EngineeringUniversity College LondonTorrington PlaceLondonWC1E 7JEUnited Kingdom
| | - Linlin Xu
- EPSRC “Frontier Engineering” Centre for Nature Inspired EngineeringDepartment of Chemical EngineeringUniversity College LondonTorrington PlaceLondonWC1E 7JEUnited Kingdom
| | - Marc‐Olivier Coppens
- EPSRC “Frontier Engineering” Centre for Nature Inspired EngineeringDepartment of Chemical EngineeringUniversity College LondonTorrington PlaceLondonWC1E 7JEUnited Kingdom
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3
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Montgomery CL, Amtawong J, Jordan AM, Kurtz DA, Dempsey JL. Proton transfer kinetics of transition metal hydride complexes and implications for fuel-forming reactions. Chem Soc Rev 2023; 52:7137-7169. [PMID: 37750006 DOI: 10.1039/d3cs00355h] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Proton transfer reactions involving transition metal hydride complexes are prevalent in a number of catalytic fuel-forming reactions, where the proton transfer kinetics to or from the metal center can have significant impacts on the efficiency, selectivity, and stability associated with the catalytic cycle. This review correlates the often slow proton transfer rate constants of transition metal hydride complexes to their electronic and structural descriptors and provides perspective on how to exploit these parameters to control proton transfer kinetics to and from the metal center. A toolbox of techniques for experimental determination of proton transfer rate constants is discussed, and case studies where proton transfer rate constant determination informs fuel-forming reactions are highlighted. Opportunities for extending proton transfer kinetic measurements to additional systems are presented, and the importance of synergizing the thermodynamics and kinetics of proton transfer involving transition metal hydride complexes is emphasized.
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Affiliation(s)
- Charlotte L Montgomery
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Jaruwan Amtawong
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Aldo M Jordan
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Daniel A Kurtz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
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4
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Hong W, Luthra M, Jakobsen JB, Madsen MR, Castro AC, Hammershøj HCD, Pedersen SU, Balcells D, Skrydstrup T, Daasbjerg K, Nova A. Exploring the Parameters Controlling Product Selectivity in Electrochemical CO 2 Reduction in Competition with Hydrogen Evolution Employing Manganese Bipyridine Complexes. ACS Catal 2023; 13:3109-3119. [PMID: 36910875 PMCID: PMC9990071 DOI: 10.1021/acscatal.2c05951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/30/2023] [Indexed: 02/18/2023]
Abstract
Selective reduction of CO2 is an efficient solution for producing nonfossil-based chemical feedstocks and simultaneously alleviating the increasing atmospheric concentration of this greenhouse gas. With this aim, molecular electrocatalysts are being extensively studied, although selectivity remains an issue. In this work, a combined experimental-computational study explores how the molecular structure of Mn-based complexes determines the dominant product in the reduction of CO2 to HCOOH, CO, and H2. In contrast to previous Mn(bpy-R)(CO)3Br catalysts containing alkyl amines in the vicinity of the Br ligand, here, we report that bpy-based macrocycles locking these amines at the side opposite to the Br ligand change the product selectivity from HCOOH to H2. Ab initio molecular dynamics simulations of the active species showed that free rotation of the Mn(CO)3 moiety allows for the approach of the protonated amine to the reactive center yielding a Mn-hydride intermediate, which is the key in the formation of H2 and HCOOH. Additional studies with DFT methods showed that the macrocyclic moiety hinders the insertion of CO2 to the metal hydride favoring the formation of H2 over HCOOH. Further, our results suggest that the minor CO product observed experimentally is formed when CO2 adds to Mn on the side opposite to the amine ligand before protonation. These results show how product selectivity can be modulated by ligand design in Mn-based catalysts, providing atomistic details that can be leveraged in the development of a fully selective system.
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Affiliation(s)
- Wanwan Hong
- Carbon Dioxide Activation Center (CADIAC), Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Mahika Luthra
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, 0315 Oslo, Norway
| | - Joakim B Jakobsen
- Carbon Dioxide Activation Center (CADIAC), Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Monica R Madsen
- Carbon Dioxide Activation Center (CADIAC), Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Abril C Castro
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, 0315 Oslo, Norway
| | - Hans Christian D Hammershøj
- Carbon Dioxide Activation Center (CADIAC), Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Steen U Pedersen
- Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
| | - David Balcells
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, 0315 Oslo, Norway
| | - Troels Skrydstrup
- Carbon Dioxide Activation Center (CADIAC), Novo Nordisk Foundation (NNF) CO2 Research Center, Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Kim Daasbjerg
- Novo Nordisk Foundation (NNF) CO2 Research Center, Interdisciplinary Nanoscience Center, Department of Chemistry, Aarhus University, Gustav Wieds Vej 10C, 8000 Aarhus C, Denmark
| | - Ainara Nova
- Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, 0315 Oslo, Norway.,Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, 0315 Oslo, Norway
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5
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Pattanayak S, Berben LA. Pre-Equilibrium Reaction Mechanism as a Strategy to Enhance Rate and Lower Overpotential in Electrocatalysis. J Am Chem Soc 2023; 145:3419-3426. [PMID: 36734988 PMCID: PMC9936576 DOI: 10.1021/jacs.2c10942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pre-equilibrium reaction kinetics enable the overall rate of a catalytic reaction to be orders of magnitude faster than the rate-determining step. Herein, we demonstrate how pre-equilibrium kinetics can be applied to breaking the linear free-energy relationship (LFER) for electrocatalysis, leading to rate enhancement 5 orders of magnitude and lowering of overpotential to approximately thermoneutral. This approach is applied to pre-equilibrium formation of a metal-hydride intermediate to achieve fast formate formation rates from CO2 reduction without loss of selectivity (i.e., H2 evolution). Fast pre-equilibrium metal-hydride formation, at 108 M-1 s-1, boosts the CO2 electroreduction to formate rate up to 296 s-1. Compared with molecular catalysts that have similar overpotential, this rate is enhanced by 5 orders of magnitude. As an alternative comparison, overpotential is lowered by ∼50 mV compared to catalysts with a similar rate. The principles elucidated here to obtain pre-equilibrium reaction kinetics via catalyst design are general. Design and development that builds on these principles should be possible in both molecular homogeneous and heterogeneous electrocatalysis.
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6
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Jing W, Shen H, Qin R, Wu Q, Liu K, Zheng N. Surface and Interface Coordination Chemistry Learned from Model Heterogeneous Metal Nanocatalysts: From Atomically Dispersed Catalysts to Atomically Precise Clusters. Chem Rev 2022; 123:5948-6002. [PMID: 36574336 DOI: 10.1021/acs.chemrev.2c00569] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The surface and interface coordination structures of heterogeneous metal catalysts are crucial to their catalytic performance. However, the complicated surface and interface structures of heterogeneous catalysts make it challenging to identify the molecular-level structure of their active sites and thus precisely control their performance. To address this challenge, atomically dispersed metal catalysts (ADMCs) and ligand-protected atomically precise metal clusters (APMCs) have been emerging as two important classes of model heterogeneous catalysts in recent years, helping to build bridge between homogeneous and heterogeneous catalysis. This review illustrates how the surface and interface coordination chemistry of these two types of model catalysts determines the catalytic performance from multiple dimensions. The section of ADMCs starts with the local coordination structure of metal sites at the metal-support interface, and then focuses on the effects of coordinating atoms, including their basicity and hardness/softness. Studies are also summarized to discuss the cooperativity achieved by dual metal sites and remote effects. In the section of APMCs, the roles of surface ligands and supports in determining the catalytic activity, selectivity, and stability of APMCs are illustrated. Finally, some personal perspectives on the further development of surface coordination and interface chemistry for model heterogeneous metal catalysts are presented.
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Affiliation(s)
- Wentong Jing
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and National & Local Joint Engineering Research Center for Preparation Technology of Nanomaterials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Hui Shen
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and National & Local Joint Engineering Research Center for Preparation Technology of Nanomaterials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Ruixuan Qin
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and National & Local Joint Engineering Research Center for Preparation Technology of Nanomaterials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Qingyuan Wu
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and National & Local Joint Engineering Research Center for Preparation Technology of Nanomaterials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361102, China
| | - Kunlong Liu
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and National & Local Joint Engineering Research Center for Preparation Technology of Nanomaterials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Nanfeng Zheng
- State Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, and National & Local Joint Engineering Research Center for Preparation Technology of Nanomaterials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
- Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen 361102, China
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7
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Abstract
This tutorial review showcases recent (2015-2021) work describing ligand construction as it relates to the design of secondary coordination spheres (SCSs). Metalloenzymes, for example, utilize SCSs to stabilize reactive substrates, shuttle small molecules, and alter redox properties, promoting functional activity. In the realm of biomimetic chemistry, specific incorporation of SCS residues (e.g., Brønsted or Lewis acid/bases, crown ethers, redox groups etc.) has been shown to be equally critical to function. This contribution illustrates how fundamental advances in organic and inorganic chemistry have been used for the construction of such SCSs. These imaginative contributions have driven exciting findings in many transformations relevant to clean fuel generation, including small molecule (e.g., H+, N2, CO2, NOx, O2) reduction. In most cases, these reactions occur cooperatively, where both metal and ligand are requisite for substrate activation.
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Affiliation(s)
- Marcus W Drover
- Department of Chemistry and Biochemistry, The University of Windsor, 401 Sunset Avenue, Windsor, ON, N9B 3P4, Canada.
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8
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Abstract
Electrocatalysis is an indispensable technique for small-molecule transformations, which are essential for the sustainability of society. Electrocatalysis utilizes electricity as an energy source for chemical reactions. Hydrogen is considered the “fuel for the future,” and designing electrocatalysts for hydrogen production has thus become critical. Furthermore, fuel cells are promising energy solutions that require robust electrocatalysts for key fuel cell reactions such as the interconversion of oxygen to water. Concerns regarding the rising concentration of atmospheric carbon dioxide have prompted the search for CO2 conversion methods. One promising approach is the electrochemical conversion of CO2 into commodity chemicals and/or liquid fuels, but such chemistry is highly energy demanding because of the thermodynamic stability of CO2. All of the above-mentioned electrocatalytic processes rely on the selective input of multiple protons (H+) and electrons (e–) to yield the desired products. Biological enzymes evolved in nature to perform such redox catalysis and have inspired the design of catalysts at the molecular and atomic levels. While it is synthetically challenging to mimic the exact biological environment, incorporating functional outer coordination spheres into molecular catalysts has shown promise for advancing multi-H+ and multi-e– electrocatalysis. From this Perspective, herein, catalysts with outer coordination sphere(s) are selected as the inspiration for developing new catalysts, particularly for the reductive conversion of H+, O2, and CO2, which are highly relevant to sustainability. The recent progress in electrocatalysis and opportunities to explore beyond the second coordination sphere are also emphasized.
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Affiliation(s)
- Soumalya Sinha
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221, USA
| | - Caroline K Williams
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221, USA
| | - Jianbing Jimmy Jiang
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH 45221, USA
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9
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Johnson EM, Liu JJ, Samuel AD, Haiges R, Marinescu SC. Switching Catalyst Selectivity via the Introduction of a Pendant Nitrophenyl Group. Inorg Chem 2022; 61:1316-1326. [PMID: 35021006 DOI: 10.1021/acs.inorgchem.1c02636] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The conversion of abundant small molecules to value-added products serves as an attractive method to store renewable energy in chemical bonds. A family of macrocyclic cobalt aminopyridine complexes was previously reported to reduce CO2 to CO with 98% faradaic efficiency through the formation of hydrogen-bonding networks and with the number of secondary amines affecting catalyst performance. One of these aminopyridine macrocycles, (NH)1(NMe)3-bridged calix[4]pyridine (L5), was modified with a nitrophenyl group to form LNO2 and metalated with a cobalt(II) precursor to generate CoLNO2, which would allow for probing the positioning and steric effects on catalysis. The addition of a nitrophenyl moiety to the ligand backbone results in a drastic shift in selectivity. Large current increases in the presence of added protons and CoLNO2 are observed under both N2 and CO2. The current increases under N2 are ∼30 times larger than the ones under CO2, suggesting a change in the selectivity of CoLNO2 to favor H2 production versus CO2 reduction. H2 is determined to be the dominant reduction product by gas chromatography, reaching faradaic efficiencies up to 76% under N2 with TFE and 71% under CO2 with H2O, in addition to small amounts of formate. X-ray photoelectron spectroscopy (XPS) reveals the presence of a cobalt-containing heterogeneous deposit on the working electrode surface, indicating the addition of the nitrophenyl group reduces the electrochemical stability of the catalyst. These observed catalytic behaviors are demonstrably different relative to the tetra-NH bridged macrocycle, which shows 98% faradaic efficiency for CO2-to-CO conversion with TFE, highlighting the importance of pendant hydrogen bond donors and electrochemically robust functional groups for selective CO2 conversion.
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Affiliation(s)
- Eric M Johnson
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Jeffrey J Liu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Adam D Samuel
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Ralf Haiges
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Smaranda C Marinescu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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10
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Liu JJ, Chapovetsky A, Haiges R, Marinescu SC. Effects of Protonation State on Electrocatalytic CO 2 Reduction by a Cobalt Aminopyridine Macrocyclic Complex. Inorg Chem 2021; 60:17517-17528. [PMID: 34761920 DOI: 10.1021/acs.inorgchem.1c01977] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A critical component in the reduction of CO2 to CO and H2O is the delivery of 2 equiv of protons and electrons to the CO2 molecule. The timing and sequencing of these proton and electron transfer steps are essential factors in directing the activity and selectivity for catalytic CO2 reduction. In previous studies, we have reported a series of macrocyclic aminopyridine cobalt complexes capable of reducing CO2 to CO with high faradaic efficiencies. Kinetic investigations reveal a relationship between the observed rate constant (kobs) and the number of pendant amine hydrogen bond donors minus one, suggesting the presence of a deprotonated active catalytic state. Herein, we investigate the feasibility of these proposed deprotonated complexes toward CO2 reduction. Two deprotonated derivatives, Co(L4-) and Co(L2-), of the tetraamino macrocycle Co(L) were independently synthesized and structurally characterized revealing extensive delocalization of the negative charge upon deprotonation. 1H nuclear magnetic resonance spectroscopy and ultraviolet-visible titration studies confirm that under catalytic conditions, the active form of the catalyst gradually becomes deprotonated, supporting thus the ndonor - 1 relationship with kobs. Electrochemical studies of Co(L4-) reveal that this deprotonated analogue is competent for electrocatalysis upon addition of an exogenous weak acid source, such as 2,2,2-trifluoroethanol, resulting in faradaic efficiencies for CO2-to-CO conversion identical to those observed with the fully protonated derivative (>98%).
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Affiliation(s)
- Jeffrey J Liu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Alon Chapovetsky
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Ralf Haiges
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - Smaranda C Marinescu
- Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
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11
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Amanullah S, Saha P, Dey A. Activating the Fe(I) State of Iron Porphyrinoid with Second-Sphere Proton Transfer Residues for Selective Reduction of CO 2 to HCOOH via Fe(III/II)-COOH Intermediate(s). J Am Chem Soc 2021; 143:13579-13592. [PMID: 34410125 DOI: 10.1021/jacs.1c04392] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The ability to tune the selectivity of CO2 reduction by first-row transition metal-based complexes via the inclusion of second-sphere effects heralds exciting and sought-after possibilities. On the basis of the mechanistic understanding of CO2 reduction by iron porphyrins developed by trapping and characterizing the intermediates involved ( J. Am. Chem. Soc. 2015, 137, 11214), a porphyrinoid ligand is envisaged to switch the selectivity of the iron porphyrins by reducing CO2 from CO to HCOOH as well as lower the overpotential to the process. The results show that the iron porphyrinoid designed can catalyze the reduction of CO2 to HCOOH using water as the proton source with 97% yield with no detectable H2 or CO. The iron porphyrinoid can activate CO2 in its Fe(I) state resulting in very low overpotential for CO2 reduction in contrast to all reported iron porphyrins, which can reduce CO2 in their Fe(0) state. Intermediates involved in CO2 reduction, Fe(III)-COOH and a Fe(II)-COOH, are identified with in situ FTIR-SEC and subsequently chemically generated and characterized using FTIR, resonance Raman, and Mössbauer spectroscopy. The mechanism of the reaction helps elucidate a key role played by a closely placed proton transfer residue in aiding CO2 binding to Fe(I), stabilizing the intermediates, and determining the fate of a rate-determining Fe(II)-COOH intermediate.
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Affiliation(s)
- Sk Amanullah
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja SC Mullick Road, Kolkata, West Bengal 700032, India
| | - Paramita Saha
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja SC Mullick Road, Kolkata, West Bengal 700032, India
| | - Abhishek Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja SC Mullick Road, Kolkata, West Bengal 700032, India
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12
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Cesari C, Shon JH, Zacchini S, Berben LA. Metal carbonyl clusters of groups 8-10: synthesis and catalysis. Chem Soc Rev 2021; 50:9503-9539. [PMID: 34259674 DOI: 10.1039/d1cs00161b] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In this review article, we discuss advances in the chemistry of metal carbonyl clusters (MCCs) spanning the last three decades, with an emphasis on the more recent reports and those involving groups 8-10 elements. Synthetic methods have advanced and been refined, leading to higher-nuclearity clusters and a wider array of structures and nuclearities. Our understanding of the electronic structure in MCCs has advanced to a point where molecular chemistry tools and other advanced tools can probe their properties at a level of detail that surpasses that possible with other nanomaterials and solid-state materials. MCCs therefore advance our understanding of structure-property-reactivity correlations in other higher-nuclearity materials. With respect to catalysis, this article focuses only on homogeneous applications, but it includes both thermally and electrochemically driven catalysis. Applications in thermally driven catalysis have found success where the reaction conditions stabilise the compounds toward loss of CO. In more recent years, MCCs, which exhibit delocalised bonding and possess many electron-withdrawing CO ligands, have emerged as very stable and effective for reductive electrocatalysis reactions since reduction often strengthens M-C(O) bonds and since room-temperature reaction conditions are sufficient for driving the electrocatalysis.
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Affiliation(s)
- Cristiana Cesari
- Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy.
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13
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Tinnermann H, Sung S, Csókás D, Toh ZH, Fraser C, Young RD. Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds. J Am Chem Soc 2021; 143:10700-10708. [PMID: 34251818 DOI: 10.1021/jacs.1c04815] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)3(PMe3)2] (1), supported by weakly coordinating [BArF20] anions, [1·M][BArF20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)3(PMe3)2][BArF20], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1·M][BArF20] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation.
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Affiliation(s)
- Hendrik Tinnermann
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Simon Sung
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Dániel Csókás
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Zhi Hao Toh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Craig Fraser
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
| | - Rowan D Young
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
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14
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Pattanayak S, Berben LA. Cobalt Carbonyl Clusters Enable Independent Control of Two Proton Transfer Rates in the Mechanism for Hydrogen Evolution. ChemElectroChem 2021. [DOI: 10.1002/celc.202100402] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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15
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Loewen ND, Pattanayak S, Herber R, Fettinger JC, Berben LA. Quantification of the Electrostatic Effect on Redox Potential by Positive Charges in a Catalyst Microenvironment. J Phys Chem Lett 2021; 12:3066-3073. [PMID: 33750139 DOI: 10.1021/acs.jpclett.1c00406] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Charged functional groups in the secondary coordination sphere (SCS) of a heterogeneous nanoparticle or homogeneous electrocatalyst are of growing interest due to enhancements in reactivity that derive from specific interactions that stabilize substrate binding or charged intermediates. At the same time, accurate benchmarking of electrocatalyst systems most often depends on the development of linear free-energy scaling relationships. However, the thermodynamic axis in those kinetic-thermodynamic correlations is most often obtained by a direct electrochemical measurement of the catalyst redox potential and might be influenced by electrostatic effects of a charged SCS. In this report, we systematically probe positive charges in a SCS and their electrostatic contributions to the electrocatalyst redox potential. A series of 11 iron carbonyl clusters modified with charged and uncharged ligands was probed, and a linear correlation between the νCO absorption band energy and electrochemical redox potentials is observed except where the SCS is positively charged.
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Affiliation(s)
- Natalia D Loewen
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
| | - Santanu Pattanayak
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
| | - Rolfe Herber
- Racah Institute of Physics, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - James C Fettinger
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
| | - Louise A Berben
- Department of Chemistry, University of California, 1 Shields Avenue, Davis, California 95616, United States
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16
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Chaturvedi A, Williams CK, Devi N, Jiang JJ. Effects of Appended Poly(ethylene glycol) on Electrochemical CO 2 Reduction by an Iron Porphyrin Complex. Inorg Chem 2021; 60:3843-3850. [PMID: 33629857 DOI: 10.1021/acs.inorgchem.0c03612] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrochemical carbon dioxide (CO2) reduction is a sustainable approach for transforming atmospheric CO2 into chemical feedstocks and fuels. To overcome the kinetic barriers of electrocatalytic CO2 reduction, catalysts with high selectivity, activity, and stability are needed. Here, we report an iron porphyrin complex, FePEGP, with a poly(ethylene glycol) unit in the second coordination sphere, as a highly selective and active electrocatalyst for the electrochemical reduction of CO2 to carbon monoxide (CO). Controlled-potential electrolysis using FePEGP showed a Faradaic efficiency of 98% and a current density of -7.8 mA/cm2 at -2.2 V versus Fc/Fc+ in acetonitrile using water as the proton source. The maximum turnover frequency was calculated to be 1.4 × 105 s-1 using foot-of-the-wave analysis. Distinct from most other catalysts, the kinetic isotope effect (KIE) study revealed that the protonation step of the Fe-CO2 adduct is not involved in the rate-limiting step. This model shows that the PEG unit as the secondary coordination sphere enhances the catalytic kinetics and thus is an effective design for electrocatalytic CO2 reduction.
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Affiliation(s)
- Ashwin Chaturvedi
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati 45221, Ohio, United States
| | - Caroline K Williams
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati 45221, Ohio, United States
| | - Nilakshi Devi
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati 45221, Ohio, United States
| | - Jianbing Jimmy Jiang
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati 45221, Ohio, United States
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17
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Lashgari A, Williams CK, Glover JL, Wu Y, Chai J, Jiang JJ. Enhanced Electrocatalytic Activity of a Zinc Porphyrin for CO 2 Reduction: Cooperative Effects of Triazole Units in the Second Coordination Sphere. Chemistry 2020; 26:16774-16781. [PMID: 32701198 DOI: 10.1002/chem.202002813] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Indexed: 11/05/2022]
Abstract
The control of the second coordination sphere in a coordination complex plays an important role in improving catalytic efficiency. Herein, we report a zinc porphyrin complex ZnPor8T with multiple flexible triazole units comprising the second coordination sphere, as an electrocatalyst for the highly selective electrochemical reduction of carbon dioxide (CO2 ) to carbon monoxide (CO). This electrocatalyst converted CO2 to CO with a Faradaic efficiency of 99 % and a current density of -6.2 mA cm-2 at -2.4 V vs. Fc/Fc+ in N,N-dimethylformamide using water as the proton source. Structure-function relationship studies were carried out on ZnPor8T analogs containing different numbers of triazole units and distinct triazole geometries; these unveiled that the triazole units function cooperatively to stabilize the CO2 -catalyst adduct in order to facilitate intramolecular proton transfer. Our findings demonstrate that incorporating triazole units that function in a cooperative manner is a versatile strategy to enhance the activity of electrocatalytic CO2 conversion.
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Affiliation(s)
- Amir Lashgari
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH, 45221, United States
| | - Caroline K Williams
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH, 45221, United States
| | - Jenna L Glover
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH, 45221, United States
| | - Yueshen Wu
- Department of Chemistry, Yale University, New Haven, Connecticut, 06520, United States
| | - Jingchao Chai
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH, 45221, United States
| | - Jianbing Jimmy Jiang
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, OH, 45221, United States
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18
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Kumar Pandey I, Kumar A, Choudhury J. Electrocatalytic CO 2 Reduction with a Half-Sandwich Cobalt Catalyst: Selectivity towards CO. Chem Asian J 2020; 15:904-909. [PMID: 32040262 DOI: 10.1002/asia.201901805] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/09/2020] [Indexed: 12/30/2022]
Abstract
We present herein a Cp*Co(III)-half-sandwich catalyst system for electrocatalytic CO2 reduction in aqueous acetonitrile solution. In addition to an electron-donating Cp* ligand (Cp*=pentamethylcyclopentadienyl), the catalyst featured a proton-responsive pyridyl-benzimidazole-based N,N-bidentate ligand. Owing to the presence of a relatively electron-rich Co center, the reduced Co(I)-state was made prone to activate the electrophilic carbon center of CO2 . At the same time, the proton-responsive benzimidazole scaffold was susceptible to facilitate proton-transfer during the subsequent reduction of CO2 . The above factors rendered the present catalyst active toward producing CO as the major product over the other potential 2e/2H+ reduced product HCOOH, in contrast to the only known similar half-sandwich CpCo(III)-based CO2 -reduction catalysts which produced HCOOH selectively. The system exhibited a Faradaic efficiency (FE) of about 70% while the overpotential for CO production was found to be 0.78 V, as determined by controlled-potential electrolysis.
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Affiliation(s)
- Indresh Kumar Pandey
- Organometallics & Smart Materials Laboratory, Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, 462 066, India
| | - Abhishek Kumar
- Organometallics & Smart Materials Laboratory, Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, 462 066, India
| | - Joyanta Choudhury
- Organometallics & Smart Materials Laboratory, Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, 462 066, India
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