Electrocatalytic Oxidation of Formate with Nickel Diphosphine Dipeptide Complexes: Effect of Ligands Modified with Amino Acids

Galan, Brandon R.; Reback, Matthew L.; Jain, Avijita; Appel, Aaron M.; Shaw, Wendy J.

doi:10.1002/ejic.201300751

Cited by 19 publications

(13 citation statements)

References 48 publications

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“…67 Such a pathway is, however, at variance with that based on CO 2 insertion in a metal−hydride bond reported for other catalysts for CO 2 hydrogenation catalysts 31,68−70 or electrocatalysts for formic acid production. 30,55 In this mechanism, as well as in the reverse mechanism proposed for formate oxidation catalyzed by nickel bisdiphosphine complexes with similar pendant amine residues, 24,41,71 formate binds to the metal center through an oxygen atom, and formate release has sometimes been found as the rate-determining step. 30 Rather, the catalytic pathway proposed here resembles the mechanism followed by catalytic hydride donors based on dihydropyridine moieties, 72,73 in which hydride transfer can be assisted by hydrogen-bonded water molecules.…”

Section: ■ Results and Discussionmentioning

confidence: 88%

“…Most molecular CO 2 -reducing catalysts produce CO. In addition to enzymes, there are few synthetic catalysts that generate formic acid, ,,− ,− and among them only two are selective and based on an Earth-abundant metal. ,, Nickel bis-diphosphine complexes bearing pendant amine groups, [Ni(P R 2 N R ′ 2 ) 2 ] 2+ , have been shown to catalyze the reverse reaction, i.e., formate oxidation, quite efficiently, ,, and this was related to the fact that the corresponding Ni II -hydride species have lower hydridicities than formic acid (Δ G ° H – = 44 kcal mol –1 in CH 3 CN) . Such low hydridicities explain also why [Ni(P R 2 N R ′ 2 ) 2 ] 2+ complexes require strong acids to evolve hydrogen in CH 3 CN under electro-assisted conditions.…”

Section: Discussionmentioning

confidence: 99%

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Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

et al. 2017

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We report here on a new series of CO-reducing molecular catalysts based on Earth-abundant elements that are very selective for the production of formic acid in dimethylformamide (DMF)/water mixtures (Faradaic efficiency of 90 ± 10%) at moderate overpotentials (500-700 mV in DMF measured at the middle of the catalytic wave). The [CpCo(PN)I] compounds contain diphosphine ligands, PN, with two pendant amine residues that act as proton relays during CO-reduction catalysis and tune their activity. Four different PN ligands with cyclohexyl or phenyl substituents on phosphorus and benzyl or phenyl substituents on nitrogen were employed, and the compound with the most electron-donating phosphine ligand and the most basic amine functions performs best among the series, with turnover frequency >1000 s. State-of-the-art benchmarking of catalytic performances ranks this new class of cobalt-based complexes among the most promising CO-to-formic acid reducing catalysts developed to date; addressing the stability issues would allow further improvement. Mechanistic studies and density functional theory simulations confirmed the role of amine groups for stabilizing key intermediates through hydrogen bonding with water molecules during hydride transfer from the Co center to the CO molecule.

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Section: ■ Results and Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

et al. 2017

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“…Addition of Hg in the Ru / 2 /HA – /H 2 A system induces no significant change in the photocatalytic activity, ruling out the involvement of cobalt metallic colloids into the H 2 production (Figure S12 and Supporting Information). In addition, the absence of any induction period and the fact that no significant H 2 evolution was observed when 2 is substituted by a simple cobalt salt, such as CoCl 2 ·6H 2 O, compared to H 2 produced from a Ru /HA – /H 2 A solution (Table S4), are also clear indications that no Co(0) nanoparticules are formed during photocatalysis with 2 …”

Section: Resultsmentioning

confidence: 98%

Cobalt(II) Pentaaza-Macrocyclic Schiff Base Complex as Catalyst for Light-Driven Hydrogen Evolution in Water: Electrochemical Generation and Theoretical Investigation of the One-Electron Reduced Species

et al. 2019

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We previously reported that the tetraazamacrocyclic Schiff base complex [Co III (CR14)(X) 2 ] n+ (CR14 = 2, 12-dimethyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),2,11,13,15-pentaene, X = Cl) is a very efficient H 2 -evolving catalyst (HEC) in fully aqueous solutions at pH 4.0−4.5 when used in a photocatalytic system including a photosensitizer and ascorbate as sacrificial electron donor. The excellent H 2evolving activity of this complex, compared to other cobalt and rhodium catalysts studied in the same photocatalytic conditions, can be related to the high stability of its twoelectron reduced form, the putative "Co(I)" state. These very interesting results led us to investigate the H 2 -evolving performances of a series of compounds from a close-related family, the pentaaza-macrocyclic cobalt [Co II (CR15)(H 2 O) 2 ]Cl 2 complex (2, CR15 = 2, 13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene), which comprises a larger macrocycle with five nitrogen atoms instead of four. Electrochemical as well as spectroscopic investigations in CH 3 CN coupled to density functional theory (DFT) calculations point to decoordination of one of the amine upon reduction of Co(II) to the low-valent "Co(I)" form. The resulting unchelated amine could potentially act as a proton relay promoting the H 2 formation via proton-coupled-electron transfer (PCET) reactions. Besides, the iron, manganese, and zinc analogues, [Fe II (CR15)(X) 2 ] n+ (X = Cl (n = 0) or H 2 O (n = 2)) (3), [Mn II (CR15)(CH 3 CN) 2 ](PF 6 ) 2 (4), and {[Zn II (CR15)Cl](PF 6 )} n (5) were also synthesized and investigated. The photocatalytic activity of 2−5 toward proton reduction was then evaluated in a tricomponent system containing the [Ru II (bpy) 3 ]Cl 2 photosensitizer and ascorbate, in fully aqueous solution. The photocatalytic activity of 2 was also compared with that of 1 in the same experimental conditions. It was found that the number of catalytic cycles versus catalyst for 2 are slightly lower than that for 1, suggesting that if the amine released upon reduction of 2 plays a role in promoting the H 2 -evolving catalytic activity, other factors balance this effect. Finally, photophysical and nanosecond transient absorption spectroscopies were used to investigate the photocatalytic system.

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“…While this review focuses on molecular catalysts which were specifically examined for electrochemical CO 2 reduction, secondary-sphere effects have been successfully harnessed in related catalytic processes, including thermal CO 2 hydrogenation (Himeda et al, 2004, 2005, 2007; Hull et al, 2012; Wang et al, 2012, 2013, 2014; Manaka et al, 2014; Suna et al, 2014; Cammarota et al, 2017), hydrogen evolution (Curtis et al, 2003; Henry et al, 2005, 2006; Wilson et al, 2006; Fraze et al, 2007; Jacobsen et al, 2007a,b; DuBois and DuBois, 2009; Gloaguen and Rauchfuss, 2009; Helm et al, 2011; Reback et al, 2013; Ginovska-Pangovska et al, 2014), hydrogen oxidation (Curtis et al, 2003; Henry et al, 2005, 2006; Wilson et al, 2006; Fraze et al, 2007; Jacobsen et al, 2007a,b; Dutta et al, 2013, 2014; Ginovska-Pangovska et al, 2014), formate oxidation (Galan et al, 2011, 2013; Seu et al, 2012), and oxygen reduction (Collman, 1977; Collman et al, 2004; Lewis and Tolman, 2004; Mirica et al, 2004; Fukuzumi, 2013; Ray et al, 2014; Fukuzumi et al, 2015; Nam, 2015; Sahu and Goldberg, 2016; Elwell et al, 2017; Hong et al, 2017; Sinha et al, 2019) reactions. In this review, we focus on how the mechanism of CO 2 reduction relates to the type of secondary-sphere effects employed in molecular systems.…”

Section: Introductionmentioning

confidence: 99%

Secondary-Sphere Effects in Molecular Electrocatalytic CO2 Reduction

2019

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The generation of fuels and value-added chemicals from carbon dioxide (CO 2 ) using electrocatalysis is a promising approach to the eventual large-scale utilization of intermittent renewable energy sources. To mediate kinetically and thermodynamically challenging transformations of CO 2 , early reports of molecular catalysts focused primarily on precious metal centers. However, through careful ligand design, earth-abundant first-row transition metals have also demonstrated activity and selectivity for electrocatalytic CO 2 reduction. A particularly effective and promising approach for enhancement of reaction rates and efficiencies of molecular electrocatalysts for CO 2 reduction is the modulation of the secondary coordination sphere of the active site. In practice, this has been achieved through the mimicry of enzyme structures: incorporating pendent Brønsted acid/base sites, charged residues, sterically hindered environments, and bimetallic active sites have all proved to be valid strategies for iterative optimization. Herein, the development of secondary-sphere strategies to facilitate rapid and selective CO 2 reduction is reviewed with an in-depth examination of the classic [Fe(tetraphenylporphyrin)] + , [Ni(cyclam)] 2+ , Mn(bpy)(CO) 3 X, and Re(bpy)(CO) 3 X (X = solvent or halide) systems, including relevant highlights from other recently developed ligand platforms.

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Electrocatalytic Oxidation of Formate with Nickel Diphosphine Dipeptide Complexes: Effect of Ligands Modified with Amino Acids

Cited by 19 publications

References 48 publications

Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid

Cobalt(II) Pentaaza-Macrocyclic Schiff Base Complex as Catalyst for Light-Driven Hydrogen Evolution in Water: Electrochemical Generation and Theoretical Investigation of the One-Electron Reduced Species

Secondary-Sphere Effects in Molecular Electrocatalytic CO2 Reduction

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