Rhodium-catalyzed hydrogenation of carbon dioxide to formic acid

Tsai, Jing Cherng; Nicholas, Kenneth M.

doi:10.1021/ja00039a024

Cited by 238 publications

(151 citation statements)

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“…Hence, elucidation of the pathways of formic acid formation is expected to lead to understanding of reaction systems in which CO 2 and H 2 are involved and also explain effects of different ligands and additives. Theoretical investigations have so far concluded that CO 2 insertion is the rate-limiting step [20,21] or that the reaction rate does not depend on H 2 pressure, [22] in spite of the fact that strong dependence of the reaction rate on H 2 pressure has been reported for homogeneous [12,15,23] and immobilized heterogeneous catalysts. [24] Results and Discussion State of [RuA C H T U N G T R E N N U N G (dmpe) 2 H 2 ] in toluene: Figure 1 shows the IR spectrum of [RuA C H T U N G T R E N N U N G (dmpe) 2 H 2 ] in toluene at 300 K and calculated spectra of cis-and trans-[RuH 2 ] complexes (from here on (dmpe) 2 is omitted).…”

Section: A C H T U N G T R E N N U N G (Ocho) 2 ] and Trans-[ru-a C Hmentioning

confidence: 99%

Carbon Dioxide Hydrogenation Catalyzed by a Ruthenium Dihydride: A DFT and High‐Pressure Spectroscopic Investigation

Urakawa

Jutz

Laurenczy

et al. 2007

Chemistry A European J

119

103

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Reaction pathways during CO(2) hydrogenation catalyzed by the Ru dihydride complex [Ru(dmpe)(2)H(2)] (dmpe=Me(2)PCH(2)CH(2)PMe(2)) have been studied by DFT calculations and by IR and NMR spectroscopy up to 120 bar in toluene at 300 K. CO(2) and formic acid readily inserted into or reacted with the complex to form formates. Two formate complexes, cis-[Ru(dmpe)(2)(OCHO)(2)] and trans-[Ru(dmpe)(2)H(OCHO)], were formed at low CO(2) pressure (<5 bar). The latter occurred exclusively when formic acid reacted with the complex. A RuHHOCHO dihydrogen-bonded complex of the trans form was identified at H(2) partial pressure higher than about 50 bar. The trans form of the complex is suggested to play a pivotal role in the reaction pathway. Potential-energy profiles along possible reaction paths have been investigated by static DFT calculations, and lower activation-energy profiles via the trans route were confirmed. The H(2) insertion has been identified as the rate-limiting step of the overall reaction. The high energy of the transition state for H(2) insertion is attributed to the elongated Ru--O bond. The H(2) insertion and the subsequent formation of formic acid proceed via Ru(eta(2)-H(2))-like complexes, in which apparently formate ion and Ru(+) or Ru(eta(2)-H(2))(+) interact. The bond properties of involved Ru complexes were characterized by natural bond orbital analysis, and the highly ionic characters of various complexes and transition states are shown. The stability of the formate ion near the Ru center likely plays a decisive role for catalytic activity. Removal of formic acid from the dihydrogen-bonded complex (RuHHOCHO) seems to be crucial for catalytic efficiency, since formic acid can easily react with the complex to regenerate the original formate complex. Important aspects for the design of highly active catalytic systems are discussed.

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Section: A C H T U N G T R E N N U N G (Ocho) 2 ] and Trans-[ru-a C Hmentioning

confidence: 99%

Carbon Dioxide Hydrogenation Catalyzed by a Ruthenium Dihydride: A DFT and High‐Pressure Spectroscopic Investigation

Urakawa

Jutz

Laurenczy

et al. 2007

Chemistry A European J

119

103

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“…The formation of formic acid by CO 2 hydrogenation has been identified as the first reaction step in all the three different reaction systems. [12] Hence, the elucidation of the formic acid formation pathways is necessary to understand several aspects of the reaction process, like the detailed reaction mechanisms, the effects of different ligands [12,15] , the role of additives (water, alcohols, and amines) [12,16,17] , and the influence of the reactants' pressure [12,16,18] . Some detailed reaction mechanisms have been proposed to date, but discrepancies between the mechanisms and experimental observations exist, [19,20] such as the one between the theoretical assignment of CO 2 insertion to Ru hydride complex as the rate-limiting step and experimentally observed facile CO 2 insertion [21,22] .…”

Section: Introductionmentioning

confidence: 99%

Towards a Rational Design of Ruthenium CO₂ Hydrogenation Catalysts by Ab Initio Metadynamics

Urakawa

Iannuzzi

Hutter

et al. 2007

Chemistry A European J

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Complete reaction pathways relevant to CO2 hydrogenation by using a homogeneous ruthenium dihydride catalyst ([Ru(dmpe)2H2], dmpe=Me2PCH2CH2PMe2) have been investigated by ab initio metadynamics. This approach has allowed reaction intermediates to be identified and free‐energy profiles to be calculated, which provide new insights into the experimentally observed reaction pathway. Our simulations indicate that CO2 insertion, which leads to the formation of formate complexes, proceeds by a concerted insertion mechanism. It is a rapid and direct process with a relatively low activation barrier, which is in agreement with experimental observations. Subsequent H2 insertion into the formateRu complex, which leads to the formation of formic acid, instead occurs via an intermediate [Ru(η2‐H2)] complex in which the molecular hydrogen coordinates to the ruthenium center and interacts weakly with the formate group. This step has been identified as the rate‐limiting step. The reaction completes by hydrogen transfer from the [Ru(η2‐H2)] complex to the formate oxygen atom, which forms a dihydrogen‐bonded RuH⋅⋅⋅HO(CHO) complex. The activation energy for the H2 insertion step is lower for the trans isomer than for the cis isomer. A simple measure of the catalytic activity was proposed based on the structure of the transition state of the identified rate‐limiting step. From this measure, the relationship between catalysts with different ligands and their experimental catalytic activities can be explained.

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“…The accelerating effect of small amounts of added water in organic solvents has been observed in active Pd (Inoue et al, 1976), Rh (Tsai & Nicholas, 1992)] and Ru (Jessop et al, 1996) etc. systems.…”

Section: Mechanism Of Co2 Hydrogenationmentioning

confidence: 98%

“…(Leitner et al, 1994) Therefore understanding the mechanism and then developing appropriate catalyst that can be applied in water is essential to high effective catalytic system. Nicholas et al (Tsai & Nicholas, 1992) have proposed that water acts as an ancillary ligand and form hydrogen bond with oxygen of the CO2 to facilitate CO2 insertion ( Figure 5A). Lau et al found the reaction rate is enhanced by adding 20% water in THF by using TpRu(PPh3)(CH3CN)H [Tp = hydrotris(pyrazolyl)borate] as a catalyst.…”

Section: Mechanism Of Co2 Hydrogenationmentioning

confidence: 99%

Recent Advances in Transition Metal-Catalysed Homogeneous Hydrogenation of Carbon Dioxide in Aqueous Media

Wang¹,

Himeda²

2012

Hydrogenation

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Rhodium-catalyzed hydrogenation of carbon dioxide to formic acid

Cited by 238 publications

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Carbon Dioxide Hydrogenation Catalyzed by a Ruthenium Dihydride: A DFT and High‐Pressure Spectroscopic Investigation

Carbon Dioxide Hydrogenation Catalyzed by a Ruthenium Dihydride: A DFT and High‐Pressure Spectroscopic Investigation

Towards a Rational Design of Ruthenium CO₂ Hydrogenation Catalysts by Ab Initio Metadynamics

Recent Advances in Transition Metal-Catalysed Homogeneous Hydrogenation of Carbon Dioxide in Aqueous Media

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Rhodium-catalyzed hydrogenation of carbon dioxide to formic acid

Cited by 238 publications

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Carbon Dioxide Hydrogenation Catalyzed by a Ruthenium Dihydride: A DFT and High‐Pressure Spectroscopic Investigation

Carbon Dioxide Hydrogenation Catalyzed by a Ruthenium Dihydride: A DFT and High‐Pressure Spectroscopic Investigation

Towards a Rational Design of Ruthenium CO2 Hydrogenation Catalysts by Ab Initio Metadynamics

Recent Advances in Transition Metal-Catalysed Homogeneous Hydrogenation of Carbon Dioxide in Aqueous Media

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Towards a Rational Design of Ruthenium CO₂ Hydrogenation Catalysts by Ab Initio Metadynamics