Iron catalyzed CO<sub>2</sub>hydrogenation to formate enhanced by Lewis acid co-catalysts

Zhang, Yuanyuan; MacIntosh, Alex D.; Wong, Janice L.; Bielinski, Elizabeth A.; Williard, Paul G.; Mercado, Brandon Q.; Hazari, Nilay; Bernskoetter, Wesley H.

doi:10.1039/c5sc01467k

Cited by 287 publications

(273 citation statements)

References 66 publications

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“…The diiron complexes with bridging hydrides reported by Holland and Limberg react with two equivalent of CO 2 to form two µ‐1,3‐formate donors over a 20 h reaction time,, corresponding to estimated pseudo first order rate constants of which are approximately an order of magnitude faster than our case for the combined first and second hydride transfer steps. The CO 2 insertion rates of these reported hydridoiron β‐diketiminate complexes are themselves two orders of magnitude smaller than those for pincer complexes; for example, one (PNP)FeCO dihydride complex reacts to completion within 25 min and has been calculated to proceed by an outer‐sphere pathway , . The tripodal phosphane‐ligated iron hydride reacts to completion with CO 2 in 12 h; the lower limit for the estimated rate constant is comparable to 1 .…”

Section: Resultsmentioning

confidence: 90%

“…Although tempting to draw conclusions on mechanism as either inner or outer sphere from this literature comparison, this analysis is arguably complicated by the relative bond dissociation free energies for the differing M–H species. We sought then to compare our values to those for reported iron hydride species , . To our knowledge, no such kinetic study has been reported for an iron hydride complex.…”

Section: Resultsmentioning

confidence: 99%

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Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Hong

Murray

2019

Eur J Inorg Chem

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The reduction of CO2 to formic acid by transition metal hydrides is a potential pathway to access reactive C1 compounds. To date, no kinetic study has been reported for insertion of a bridging hydride in a weak‐field ligated complex into CO2; such centers have relevance to metalloenzymes that catalyze this reaction. Herein, we report the kinetic study of the reaction of a tri(µ‐hydride)triiron(II/II/II) cluster supported by a tris(β‐diketimine) cyclophane (1) with CO2 monitored by 1H‐NMR and temperature‐controlled UV/Vis spectroscopy. We found that 1 reacts with CO2 to traverse the reported monoformate (1‐CO2) and a diformate complex (1‐2CO2) at 298 K in toluene, and ultimately yields the triformate species (1‐3CO2) at elevated temperature. The second order rate constant, H/D kinetic isotope effect, ΔH‡, and ΔS‡ for formation of 1‐CO2 were determined as 8.4(3) × 10–4 m–1 s–1, 1.08(9), 11(1) kcal mol–1, and –3(1) × 10 cal mol–1 K–1, respectively at 298 K. These parameters suggest that CO2 coordination to the iron centers does not coordinate prior to the rate controlling step whereas Fe–H bond cleavage does.

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Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Hong

Murray

2019

Eur J Inorg Chem

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“…The proton NMR shift of the N−H proton is an indicator of the strength of the hydrogen bonding, with further downfield shifts indicating stronger interactions. 15 The similarity in the N−H shift in compounds 2 and 3 indicates similar hydrogen-bonding interactions in solution. From this we propose that 2 is monomeric in solution and dimerizes upon crystallization.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

1,2-Addition of Formic or Oxalic Acid to ^–N{CH₂CH₂(PiPr₂)}₂-Supported Mn(I) Dicarbonyl Complexes and the Manganese-Mediated Decomposition of Formic Acid

Tondreau

Boncella

2016

Organometallics

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PN H P)Mn(CO) 2 (I) carboxylate complexes (PN H P = HN{CH 2 CH 2 (PiPr 2 )} 2 ) were prepared via 1,2-addition of either formic or oxalic acid to (PNP)Mn(CO) 2 (PNP = the deprotonated, amide form of the ligand − N{CH 2 CH 2 (PiPr 2 )} 2 ). The structural and spectral properties of these complexes were compared. The manganese formate complex was found to be dimeric in the solid state and monomeric in solution. Half an equivalent of oxalic acid was employed to form the bridging oxalate dimanganese complex. The catalytic competencies of the carboxylate complexes were assessed, and the formate complex was found to decompose formic acid catalytically. Both dehydrogenation and dehydration pathways were active as assessed by the presence of H 2 , CO 2 , and H 2 O. The addition of LiBF 4 exhibited a strong inhibitory effect on the catalysis. C atalytic storage and release of dihydrogen from small molecules has been explored as an alternative energy source. 1 Relevant to this work is the recent progress made in the dehydrogenation of formic acid (FA) to yield H 2 and CO 2 . The original exploration of FA decomposition focused on heavier metals such as ruthenium, 2 rhodium, 3 and iridium. 4 Beller was then able to extend FA decomposition to iron, 5 followed by other groups using pincer ligands. 6 Several studies by Beller and Laurenczy have explored the fundamental properties of this reaction with iron. 7 PN H P (PN H P = HN{CH 2 CH 2 (PiPr 2 )} 2 )-supported ruthenium was also shown to be particularly active as an alcohol dehydrogenation catalyst. 8 The analogous PN H P-supported iron complex (PN H P)Fe(H)-(CO)(CO 2 H) was shown to be effective in the decomposition of formic acid and methanol/water dehydrogenation. 9 Hazari and Bernskoetter also first reported the importance of Lewis acids in the catalysis of FA decomposition. 9b This is a pointed example of how iron compounds have the ability to achieve catalytic transformations that previously had been performed by noble metals.As iron compounds supported by PN H P have successfully mirrored the FA decomposition catalysis of PN H P-supported ruthenium compounds, we sought to extend similar reactivity to isoelectronic Mn(I) complexes supported in a similar fashion. An easy extension of the iron(II) hydride/PNP amide is to use the isoelectronic Mn(I) dicarbonyl complex ( Figure 1). We recently reported the synthesis of ( iPr PN H P)Mn-(CO) 2 Br. 10 The desired amide complex was formed in a simple dehydrohalogenation step, giving ( iPr PNP)Mn(CO) 2 .We are interested in FA decomposition as a source of gas pressure to perform pressure−volume work (PV-work), e.g., to move an actuator. Although our end-goal differs from fuel cell use, the formation of two moles of gas from one mole of liquid (FA) prompted this investigation. Our PV-work requires lower temperatures than most of the previously described reaction conditions (typically 90°C or higher). Attempting the catalysis with a PNP-supported Mn(I) complex has allowed us to investigate an alternative system under conditio...

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“…[89] Hazari/Bernskoetter and co-workers showed that Fe-30, especially in the presence of aL ewis acid, such as LiOTf, catalyzes the hydrogenation of CO 2 highly efficiently (TON % 59 000). [90] Fe-30,a nalogous to Co-11,d oes not contain an acidic proton in the ligand. Activation of H 2 by anon-classical hydrogen complex was proposed, which gets deprotonated by the strong base DBU,l eading to am etal hydride complex.…”

Section: Methodsmentioning

confidence: 99%

“…Activation of H 2 by anon-classical hydrogen complex was proposed, which gets deprotonated by the strong base DBU,l eading to am etal hydride complex. [83,90] In the hydrogenation of CO 2 to formate,the most efficient Fe and Mn catalysts show similar TONs,b ut Fe-mediated reactions can proceed faster.…”

Section: Methodsmentioning

confidence: 99%

Manganese Complexes for (De)Hydrogenation Catalysis: A Comparison to Cobalt and Iron Catalysts

2017

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The sustainable use of the resources on our planet is essential. Noble metals are very rare and are diversely used in key technologies, such as catalysis. Manganese is the third most abundant transition metal of the Earth's crust and based on the recently discovered impressive reactivity in hydrogenation and dehydrogenation reactions, is a potentially useful noble-metal "replacement". The hope of novel selectivity profiles, not possible with noble metals, is also an aim of such a "replacement". The reactivity of manganese complexes in (de)hydrogenation reactions was demonstrated for the first time in 2016. Herein, we summarize the work that has been published since then and especially discuss the importance of homogeneous manganese catalysts in comparison to cobalt and iron catalysts.

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Iron catalyzed CO₂hydrogenation to formate enhanced by Lewis acid co-catalysts

Abstract: Iron/Lewis acid co-catalysts hydrogenate to CO2 to formate with unprecedented turnover for a first row transition metal catalyst.

Cited by 287 publications

References 66 publications

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

1,2-Addition of Formic or Oxalic Acid to ^–N{CH₂CH₂(PiPr₂)}₂-Supported Mn(I) Dicarbonyl Complexes and the Manganese-Mediated Decomposition of Formic Acid

Manganese Complexes for (De)Hydrogenation Catalysis: A Comparison to Cobalt and Iron Catalysts

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Iron catalyzed CO2hydrogenation to formate enhanced by Lewis acid co-catalysts

Abstract: Iron/Lewis acid co-catalysts hydrogenate to CO2 to formate with unprecedented turnover for a first row transition metal catalyst.

Cited by 287 publications

References 66 publications

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

1,2-Addition of Formic or Oxalic Acid to –N{CH2CH2(PiPr2)}2-Supported Mn(I) Dicarbonyl Complexes and the Manganese-Mediated Decomposition of Formic Acid

Manganese Complexes for (De)Hydrogenation Catalysis: A Comparison to Cobalt and Iron Catalysts

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Iron catalyzed CO₂hydrogenation to formate enhanced by Lewis acid co-catalysts

1,2-Addition of Formic or Oxalic Acid to ^–N{CH₂CH₂(PiPr₂)}₂-Supported Mn(I) Dicarbonyl Complexes and the Manganese-Mediated Decomposition of Formic Acid