More Than Just a Reagent: The Rise of Renewable Organohydrides for Catalytic Reduction of Carbon Dioxide

Ghosh, Debashis; Kumar, George Rajendra; Saravanan, S.; Tanaka, Koji

doi:10.1002/cssc.202002660

Cited by 17 publications

(6 citation statements)

References 152 publications

(374 reference statements)

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“…In particular, hydride and H atom transfer reactions are important in, for example, catalytic hydrogenation, hydroformylation, or small molecule activation reactions relevant to renewable energy storage. This has stimulated extensive research on hydride and H atom donor reagents, metal and nonmetal containing, as reducing agents during the past decades. − Inspired by natural enzymatic cofactors, for example, nicotinamide adenine dinucleotide phosphate (NADPH) or flavin adenine dinucleotide (FADH 2 ), several nonmetal hydride donors with dihydropyridines or dihydroquinoline moieties have been established . FADH 2 acts as a hydride donor in various biochemical processes.…”

Section: Introductionmentioning

confidence: 99%

A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent

et al. 2021

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The transfer of multiple electrons and protons is of crucial importance in many reactions relevant in biology and chemistry. Natural redox-active cofactors are capable of storing and releasing electrons and protons under relatively mild conditions and thus serve as blueprints for synthetic proton-coupled electron transfer (PCET) reagents. Inspired by the prominence of the 2e − / 2H + disulfide/dithiol couple in biology, we investigate herein the diverse PCET reactivity of a Re complex equipped with a bipyridine ligand featuring a unique SH••• − S moiety in the backbone. The disulfide bond in fac-[Re( S−S bpy)(CO) 3 Cl] (1, S−S bpy = [1,2]dithiino[4,3-b:5,6-b′]dipyridine) undergoes two successive reductions at equal potentials of −1.16 V vs Fc +|0 at room temperature forming [Re( S2 bpy)(CO) 3 Cl] 2− (1 2− , S2 bpy = [2,2′-bipyridine]-3,3′-bis(thiolate)). 1 2− has two adjacent thiolate functions at the bpy periphery, which can be protonated forming the S−H••• − S unit, 1H − . The disulfide/dithiol switch exhibits a rich PCET reactivity and can release a proton (ΔG°H + = 34 kcal mol −1 , pK a = 24.7), an H atom (ΔG°H • = 59 kcal mol −1 ), or a hydride ion (ΔG°H − = 60 kcal mol −1 ) as demonstrated in the reactivity with various organic test substrates.

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Section: Introductionmentioning

confidence: 99%

A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent

et al. 2021

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“…Later, [CpFe[CO) 2 ] 2 in the presence of an excess of P n Bu 3 was shown to catalyze the N -formylation of amines with CO 2 and PhSiH 3 at mild temperatures and in high yields . Our catalyst design was inspired by these results and previous work, which showed that iron(II) NHC complexes efficiently activate CO bonds, including catalytic hydrosilylation of carbonyl and ester functionalities, and the catalytic polymerization of lactones. − In the course of our work, we also identified an iron hydride upon exposure of an NHC iron complex to PhSiH 3 , a species that has often been inferred as key intermediate in the activation of CO 2 . ,− Due to these reactivity patterns, we were interested in exploring the activity of such iron NHC complexes as catalysts for the activation and functionalization of CO 2 . Here we show that these complexes are indeed useful in this catalytic CO 2 fixation, and we provide support that the active species is the actual NHC iron species rather than dissociated NHC ligand, even though the NHC on its own is an excellent catalyst for CO 2 activation and the N -formylation of amines .…”

Section: Introductionmentioning

confidence: 69%

Comparing the Activity of N-Heterocyclic Carbene Iron Complexes and Free Carbene Precursors in the Hydrosilylation of CO₂

2023

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Piano-stool iron complexes with N-heterocyclic carbene (NHC) ligands have shown high potential in the activation and conversion of CO bonds in aldehydes, ketones, and esters. Here we demonstrate the expansion of this activity to the functionalization of CO2 with amines to form N-formamide products in the presence of a silane (PhSiH3). This synthetically valuable utilization of CO2 as C1-synthon is catalyzed by iron complexes containing a variety of different NHC ligands. Structural variations of the NHC ligands did not reveal any correlation with catalytic activity, with imidazole and triazole-derived NHCs reaching similar conversions. However, the use of BF4 – as counterion in cationic complexes, and also incorporating a Cp* instead of a Cp spectator ligand led to a marked decrease in catalytic activity. While NHC iron complexes reach mediocre activity (about 50% conversion at 5% catalyst loading in 24 h), the corresponding imidazolium and triazolium carboxylates as precursors of free carbenes display excellent catalytic activity with essentially full conversion after 1 h at 1 mol % loading. Experiments at variable iron complex loading as well as carbene trapping experiments with S8 together with spectroscopic investigations demonstrated a high stability of the Fe–CNHC bond during catalysis and lend strong support to a NHC iron unit as catalytically active species rather than free NHC resulting from Fe–NHC dissociation, even though free NHCs are excellent catalysts for this reaction. Optimized of reaction conditions, in particular the addition of another equivalent of silane allowed to reach high conversions of piperidine and CO2 to N-formylpiperidine using a triazolylidene iron complex as catalyst precursor.

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“…Organoboranes, characterized by a C-BR 2 group, were first discovered as classic precursors for C–OH hydroxy groups in the early 20th century. − Organoboranes have been widely used for Suzuki–Miyaura C–C coupling in organic chemistry. − It is undeniably true that the discovery of Suzuki–Miyaura cross-coupling of aryl halides and organoboranes represented a milestone in C–C bond formation history, which was honored with Nobel Prize in 2010. − Since then, the new era of organoboranes began. − Among them, diboranes, with the formula of (RO) 2 B–B(OR) 2 , are the common borylation reagents in all kinds of organic reactions. Two most commonly used diboranes are B 2 (OH) 4 and bis(pinacolato)diborane (B 2 pin 2 ).…”

Section: Synthesis Of Diboranesmentioning

confidence: 99%

A Deeper Understanding of H₂ Evolution Entirely from Water via Diborane Hydrolysis

Liu

Zhang

et al. 2023

ACS Materials Lett.

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Hydrogen (H2) has drawn extensive attention due to its superior gravimetric capacity density and eco-friendly nature. Nowadays, hydrogen is mainly produced by the steam reforming of natural gas, a process that leads to massive emissions of greenhouse gases. Very recently, H2 evolution upon hydrolysis of diboranes (e.g., B2(OH)4 and B2pin2) is promising because both H atoms of the released H2 are obtained from water. This is different from the hydrolysis of sodium borohydride, dimethylaminoborane, ammonia borane, and tetramethyldisiloxane, where an H2 is generated with only one H atom from H2O and the other one from hydrogen storage materials. Importantly, diborane hydrolysis in D2O could provide an easy and simple method for D2 evolution. In this minireview, an overview of H2 evolution upon diborane hydrolysis with an extraordinary emphasis on the recent developments in mechanism study and applications is presented. The future research emphasis and perspectives of H2 evolution upon diborane hydrolysis have been suggested for commercialization as well.

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More Than Just a Reagent: The Rise of Renewable Organohydrides for Catalytic Reduction of Carbon Dioxide

Cited by 17 publications

References 152 publications

A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent

A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent

Comparing the Activity of N-Heterocyclic Carbene Iron Complexes and Free Carbene Precursors in the Hydrosilylation of CO₂

A Deeper Understanding of H₂ Evolution Entirely from Water via Diborane Hydrolysis

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More Than Just a Reagent: The Rise of Renewable Organohydrides for Catalytic Reduction of Carbon Dioxide

Cited by 17 publications

References 152 publications

A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent

A Bioinspired Disulfide/Dithiol Redox Switch in a Rhenium Complex as Proton, H Atom, and Hydride Transfer Reagent

Comparing the Activity of N-Heterocyclic Carbene Iron Complexes and Free Carbene Precursors in the Hydrosilylation of CO2

A Deeper Understanding of H2 Evolution Entirely from Water via Diborane Hydrolysis

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Product

Resources

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Comparing the Activity of N-Heterocyclic Carbene Iron Complexes and Free Carbene Precursors in the Hydrosilylation of CO₂

A Deeper Understanding of H₂ Evolution Entirely from Water via Diborane Hydrolysis