- Mechanism of CO2hydrogenation to formates by homogeneous Ru-PNP pincer catalyst: From a theoretical description to performance optimization
-
The reaction mechanism of CO2hydrogenation by pyridine-based Ru-PNP catalyst in the presence of DBU base promoter was studied by means of density functional theory calculations. Three alternative reaction channels promoted by the complexes potentially present under the reaction conditions, namely the dearomatized complex 2 and the products of cooperative CO2(3) and H2(4) addition, were analysed. It is shown that the bis-hydrido Ru-PNP complex 4 provides the unique lowest-energy reaction path involving a direct effectively barrierless hydrogenolysis of the polarized complex 5?. The reaction rate in this case is controlled by the CO2activation by Ru-H that proceeds with a very low barrier of ca. 20 kJ mol-1. The catalytic reaction can be hampered by the formation of a stable formato-complex 5. In this case, the rate is controlled by the H2insertion into the Ru-OCHO coordination bond, for which a barrier of 65 kJ mol-1is predicted. The DFT calculations suggest that the preference for the particular route can be controlled by varying the partial pressure of H2in the reaction mixture. Under H2-rich conditions, the former more facile catalytic path should be preferred. Dedicated kinetic experiments verify these theoretical predictions. The apparent activation energies measured at different H2/CO2molar ratios are in a perfect agreement with the calculated values. Ru-PNP is a highly active CO2hydrogenation catalyst allowing reaching turnover frequencies in the order of 106h-1at elevated temperatures. Moreover, a minor temperature dependency of the reaction rate attainable in excess H2points to the possibility of efficient CO2hydrogenation at near-ambient temperatures. This journal is
- Filonenko, Georgy A.,Hensen, Emiel J. M.,Pidko, Evgeny A.
-
-
Read Online
- A highly active non-precious transition metal catalyst for the hydrogenation of carbon dioxide to formates
-
Herein a highly active non-precious transition metal catalyst system for homogeneous hydrogenation of carbon dioxide to formate is presented. The application of selected nickel(ii) salts in combination with tailored multidentate ligands enabled the effective transformation of carbon dioxide with an exceptional TON of up to 4.65 × 106. This unprecedented productivity based on the novel nickel catalyst not only outmatches that of existing systems containing first row transition metals, but also established catalysts based on precious transition metals.
- Schieweck, Benjamin G.,Westhues, Niklas F.,Klankermayer, Jürgen
-
-
Read Online
- Aperture-Opening Encapsulation of a Transition Metal Catalyst in a Metal-Organic Framework for CO2 Hydrogenation
-
The aperture-opening process resulting from dissociative linker exchange in zirconium-based metal-organic framework (MOF) UiO-66 was used to encapsulate the ruthenium complex (tBuPNP)Ru(CO)HCl in the framework (tBuPNP = 2,6-bis((di-tert-butyl-phosphino)methyl)pyridine). The resulting encapsulated complex, [Ru]@UiO-66, was a very active catalyst for the hydrogenation of CO2 to formate. Unlike the analogous homogeneous catalyst, [Ru]@UiO-66 could be recycled five times, showed no evidence for bimolecular catalyst decomposition, and was less prone to catalyst poisoning. These results demonstrated for the first time how the aperture-opening process in MOFs can be used to synthesize host-guest materials useful for chemical catalysis.
- Li, Zhehui,Rayder, Thomas M.,Luo, Lianshun,Byers, Jeffery A.,Tsung, Chia-Kuang
-
-
Read Online
- Bio-Inspired Mn(I) Complexes for the Hydrogenation of CO2 to Formate and Formamide
-
Developing new, efficient catalysts that contain Earth-abundant metals and simple, robust ligands for CO2 hydrogenation is important to create cost-effective processes of CO2 utilization. Inspired by nature, which utilizes an ortho-OH-substituted pyridine motif in Fe-containing hydrogenases, we developed a Mn complex with a simple N-donor ligand, 6,6′-dihydroxy-2,2′-bipyridine, that acts as an efficient catalyst for CO2 hydrogenation. Turnover numbers of 6250 for hydrogenation of CO2 to formate in the presence of DBU were achieved. Moreover, hydrogenation of CO2 to formamide was achieved in the presence of a secondary amine.
- Dubey, Abhishek,Nencini, Luca,Fayzullin, Robert R.,Nervi, Carlo,Khusnutdinova, Julia R.
-
-
Read Online
- Amidines as effective ancillary ligands in copper-catalyzed hydrogenation of carbon dioxide
-
Mononuclear Cu(II) complexes bearing a bidentate bisamidine ligand were newly synthesized and characterized. The catalytic activity was evaluated in the hydrogenation of carbon dioxide to formate salts. A substantial enhancement of the catalyst turnover number was achieved by the imidazoline-based complex, indicating that amidines serve as effective ancillary ligands for homogeneous copper catalysis.
- Kayaki, Yoshihito,Kuwata, Shigeki,Watari, Ryo
-
-
Read Online
- Cellulose-dissolving protic ionic liquids as low cost catalysts for direct transesterification reactions of cellulose
-
Cellulose acetate (CA) is a resin derived from biomass. In addition to its various superior properties, CA is preferable to existing petroleum-derived resins from the viewpoint of green chemistry. Therefore, the acetylation of cellulose is one of the most important subjects in cellulose research. In this study, we found that the acetylation of cellulose could proceed in some protic ionic liquids (PILs) composed of amidine and acetic acid with ΔpKa = ca. 8.4-8.7 under mild conditions without any catalyst. The degree of substitution (DS) of the produced CA was above 1.84, and the maximum DS was 2.87 when the ΔpKa of the PIL was about 8.5. In propionate-based PILs, cellulose was not only acetylated but also propionated; however, the cellulose acetylation did not occur in formate-based PILs. It was revealed that the esterification of cellulose proceeded through the anion exchange between carboxylic anhydride and anion species of the PIL.
- Hanabusa, Hideki,Izgorodina, Ekaterina I.,Suzuki, Shiori,Takeoka, Yuko,Rikukawa, Masahiro,Yoshizawa-Fujita, Masahiro
-
-
Read Online
- Catalytic Formic Acid Dehydrogenation and CO2 Hydrogenation Using Iron PNRP Pincer Complexes with Isonitrile Ligands
-
It has previously been demonstrated that complexes of the form (iPrPNP)Fe(H)(C≡NR) (iPrPNP = N(CH2CH2P(iPr)2)2-, R = 2,6-dimethylphenyl or 4-methoxyphenyl), which contain a pincer ligand capable of metal-ligand cooperation (MLC), are active for CO2 hydrogenation. Herein, the synthesis and catalytic activity of a second-generation of precatalysts containing a tertiary amine ligand, which cannot participate in MLC, are presented. Specifically, the complexes (iPrPNMeP)Fe(H)(HBH3)(C≡NR) (iPrPNMeP = MeN(CH2CH2P(iPr)2)2, R = 2,6-dimethylphenyl (2a), tert-butyl (2b), or adamantyl (2c)) have been prepared and crystallographically characterized. These complexes are precatalysts for both formic acid dehydrogenation and CO2 hydrogenation to formate, and give improved activity compared to first-generation systems with isonitrile ligands. The second-generation systems 2a-c, however, give inferior activity compared to the related carbonyl complexes (iPrPNP)Fe(H)(CO) and (iPrPNMeP)Fe(H)(HBH3)(CO), which have been previously reported. This study demonstrates that a ligand which can participate in MLC is not universally advantageous for promoting the hydrogenation and dehydrogenation reactions studied in this work and provides guidance for the rational design of improved catalysts for reactions relevant to energy storage.
- Curley, Julia B.,Smith, Nicholas E.,Bernskoetter, Wesley H.,Hazari, Nilay,Mercado, Brandon Q.
-
-
Read Online
- Hydrogenation of carbon dioxide to formate catalyzed by a copper/1,8-diazabicyclo[5.4.0]undec-7-ene system
-
Hydrogenation of carbon dioxide to formate was achieved using copper (Cu) catalysts in the presence of strong organic bases including amidines and guanidines. Specifically, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proved to be effective for the transformation of a 1:1 mixture of hydrogen and carbon dioxide into its formate salt under increased pressure in the presence of various Cu(I) and Cu(II) salts at 100°C. A novel complex derived from copper iodide and DBU equally promoted the same reaction, indicating that DBU-Cu species are involved as real catalysts in this hydrogenation.
- Watari, Ryo,Kayaki, Yoshihito,Hirano, Shin-Ichi,Matsumoto, Norio,Ikariya, Takao
-
-
Read Online
- Cu(i) complex bearing a PNP-pincer-Type phosphaalkene ligand with a bulky fused-ring Eind group: Properties and applications to FLP-Type bond activation and catalytic CO2 reduction
-
Herein, we report the synthesis of [Cu(Eind2-BPEP)][PF6] (2) (Eind2-BPEP = 2,6-bis(2-Eind-2-phosphaethenyl)pyridine, Eind = 1,1,3,3,5,5,7,7-octaethyl-1,2,3,5,6,7-hexahydro-s-indacen-4-yl), a three-coordinated Cu(i) complex bearing a PNP-pincer-Type phosphaalkene ligand with bulky fused-ring Eind groups. The Gutmann-Beckett test revealed that complex 2 is highly Lewis acidic and comparable in strength to B(C6F5)3, which is a relatively strong Lewis acid. In addition, 2 is more Lewis acidic than [Cu(Mes?2-BPEP)][PF6] (3), the analogous complex with less-bulky Mes? instead of Eind groups. DFT calculations using model compounds revealed that the higher Lewis acidity of 2 compared to 3 is not due to the electronic effects of the ligand, but due to a reduction in the LUMO energy caused by the steric effect of the bulky Eind groups. When combined with a tertiary amine, the highly Lewis acidic and bulky 2 exhibits the reactivity of a frustrated Lewis pair (FLP) and can activate hydrogen and phenylacetylene. Complexes 2 and 3 were found to catalyze the hydrogenation and hydrosilylation of CO2 in the presence of DBU under relatively mild conditions.
- Choi, Jun-Chul,Ozawa, Fumiyuki,Takeuchi, Katsuhiko,Tanaka, Yuto,Tanigawa, Ippei
-
-
Read Online
- Carbon dioxide hydrogenation to formate catalyzed by a bench-stable, non-pincer-type Mn(I) alkylcarbonyl complex
-
The catalytic reduction of carbon dioxide is a process of growing interest for the use of this simple and abundant molecule as a renewable building block in C1-chemical synthesis and for hydrogen storage. The well-defined, bench-stable alkylcarbonyl Mn(I) bis(phosphine) complex fac-[Mn(CH2CH2CH3)(dippe)(CO)3] [dippe = 1,2-bis(diisopropylphosphino)-ethane] was tested as an efficient and selective non-precious-metal precatalyst for the hydrogenation of CO2 to formate under mild conditions (75 bar total pressure, 80 °C), in the presence of a Lewis acid co-catalyst (LiOTf) and a base (DBU). Mechanistic insight into the catalytic reaction is provided by means of density functional theory (DFT) calculations.
- Gonsalvi, Luca,Kirchner, Karl,Kostera, Sylwia,Peruzzini, Maurizio,Veiros, Luis F.,Weber, Stefan
-
-
Read Online
- Understanding the efficiency of ionic liquids-DMSO as solvents for carbohydrates: use of solvatochromic- And related physicochemical properties
-
The physical dissolution of carbohydrates (cellulose, chitin, and starch),i.e., without the formation of covalent bonds requires the solvent to possess certain physicochemical properties. Concentrating on cellulose, the solvent should act both as a Lewis acid and a Lewis base, and disrupt the present hydrophobic interactions, as the biopolymer exhibits amphiphilic characteristics. The quantification of the relative importance of these physicochemical properties helps in predicting the solvent structures, which are expected to be efficient as cellulose solvents. Ionic liquids (ILs) are extensively used as carbohydrate solvents because they disrupt the intramolecular-, intermolecular-, and hydrophobic interactions within the biopolymer structure, leading to its dissolution. Solvatochromic substances (probes) are especially sensitive to one or more of the above-mentioned biopolymer-solvent interactions. Consequently, they are used to predict and rationalize the solvent efficiency. The solvent parameters (descriptors) most widely employed are empirical polarity,ET(probe), Lewis acidity (SA); Lewis basicity (SB), dipolarity (SD), and polarizability (SP); S refers to the solvent. We synthesized 18 ILs, including derivatives of imidazole, 1,8-diazabicyclo[5.4.0]undec-7-ene, and tetramethylguanidine; the corresponding anions are carboxylates, chloride and dimethylphosphate. We used solvatochromic probes to calculate the descriptors of IL-DMSO (at fixed DMSO mole fraction of 0.6; 40 °C), and correlatedET(probe) with the other descriptors. We also tested the correlations by using a molar volume of the IL (VM) instead of SD, and the Lorentz-Lorenz refractive index functionf(n) of the IL-DMSO mixture instead of SP. The quality of the regression analysis increased noticeably when we limited the ILs correlated with those based on imidazole (13 ILs), and used (VM) andf(n). The regression coefficients showed that SA is the most important descriptor; the solvent empirical polarity is inversely dependent onVM. The value off(n) shows the importance of hydrophobic interactions. By using different probes, we showed that the observed small contribution of SB reflects the steric crowding around the positive nitrogen atoms in some probes. The results obtained help in selecting ILs as solvents for cellulose and other carbohydrates, based on the expected strength of their interactions with the biopolymers. Therefore, using solvatochromism for solvent efficiency screening saves labor and cost.
- Bioni, Thaís A.,de Oliveira, Mayara L.,Dignani, Marcella T.,El Seoud, Omar A.
-
p. 14906 - 14914
(2020/09/23)
-
- An integrated high-throughput strategy enables the discovery of multifunctional ionic liquids for sustainable chemical processes
-
Development of new chemical processes with simplified reaction systems and work-up procedures is a challenging task. Although ionic liquids are a class of potential multifunctional compounds to simplify traditional chemical processes, their rational design is difficult due to complex interactions. In this work, a proof-of-concept strategy has been proposed to achieve an integration of high-throughput preparation of ionic liquids and in situ screening of their reaction-promoting performance in 96-well plates. The integrated approach then enables a facile identification of optimal ionic liquids from a 400-ionic liquid candidate pool to act as the solvent, the catalyst and the separating assistant, simultaneously, for carbonyl-azide cycloaddition reactions. Merits of the ionic liquids-based processes have been demonstrated not only in the convenient and efficient synthesis of 1,2,3-triazolyl compounds but also in the discovery of a new reaction for the chemical post-modification of free peptides.
- Zhu, Anlian,Li, Lingjun,Zhang, Chi,Shen, Yutan,Tang, Mingjie,Bai, Lili,Du, Chunyan,Zhang, Suojiang,Wang, Jianji
-
supporting information
p. 307 - 313
(2019/01/28)
-
- A MOF-assisted phosphine free bifunctional iron complex for the hydrogenation of carbon dioxide, sodium bicarbonate and carbonate to formate
-
The hydrogenation of carbon dioxide into formic acid (FA) with Earth-abundant metals is a vibrant research area because FA is an attractive molecule for hydrogen storage. We report a cyclopentadienyl iron tricarbonyl complex that provides up to 3000 turnover number for carbon dioxide hydrogenation when combined with a catalytic amount of the chromium dicarboxylate MOF MIL-53(Cr). To date, this is the highest turnover number reported in the presence of a phosphine-free iron complex.
- Coufourier, Sébastien,Gaillard, Sylvain,Clet, Guillaume,Serre, Christian,Daturi, Marco,Renaud, Jean-Luc
-
supporting information
p. 4977 - 4980
(2019/05/21)
-
- Ionic liquid [OMIm][OAc] directly inducing oxidation cleavage of the β-O-4 bond of lignin model compounds
-
We explored the oxidation reactions of lignin model compounds directly induced by ionic liquids under metal-free conditions. In this work, it was found that ionic liquid 1-octyl-3-methylimidazolium acetate as a solvent could promote the aerobic oxidation of lignin model compound 2-phenoxyacetophenone (1) and the yields of phenol and benzoic acid from 1 could be as high as 96% and 86%, respectively. A possible reaction pathway was proposed based on a series of control experiments. An acetate anion from the ionic liquid attacked the hydrogen from the β-carbon thereby inducing the cleavage of the C-O bond of the aromatic ether. Furthermore, it was found that 2-(2-methoxyphenoxy)-1-phenylethanone (4) with a methoxyl group could also be transformed into aromatic products in this simple reaction system and the yields of phenol and benzoic acid from 4 could be as high as 98% and 85%, respectively. This work provides a simple way for efficient transformation of lignin model compounds.
- Yang, Yingying,Fan, Honglei,Meng, Qinglei,Zhang, Zhaofu,Yang, Guanying,Han, Buxing
-
supporting information
p. 8850 - 8853
(2017/08/10)
-
- Iron catalyzed CO2 hydrogenation to formate enhanced by Lewis acid co-catalysts
-
A family of iron(ii) carbonyl hydride complexes supported by either a bifunctional PNP ligand containing a secondary amine, or a PNP ligand with a tertiary amine that prevents metal-ligand cooperativity, were found to promote the catalytic hydrogenation of CO2 to formate in the presence of Bronsted base. In both cases a remarkable enhancement in catalytic activity was observed upon the addition of Lewis acid (LA) co-catalysts. For the secondary amine supported system, turnover numbers of approximately 9000 for formate production were achieved, while for catalysts supported by the tertiary amine ligand, nearly 60 000 turnovers were observed; the highest activity reported for an earth abundant catalyst to date. The LA co-catalysts raise the turnover number by more than an order of magnitude in each case. In the secondary amine system, mechanistic investigations implicated the LA in disrupting an intramolecular hydrogen bond between the PNP ligand N-H moiety and the carbonyl oxygen of a formate ligand in the catalytic resting state. This destabilization of the iron-bound formate accelerates product extrusion, the rate-limiting step in catalysis. In systems supported by ligands with the tertiary amine, it was demonstrated that the LA enhancement originates from cation assisted substitution of formate for dihydrogen during the slow step in catalysis.
- Zhang, Yuanyuan,MacIntosh, Alex D.,Wong, Janice L.,Bielinski, Elizabeth A.,Williard, Paul G.,Mercado, Brandon Q.,Hazari, Nilay,Bernskoetter, Wesley H.
-
p. 4291 - 4299
(2015/06/25)
-
- Homogeneous hydrogenation of CO2 to methyl formate utilizing switchable ionic liquids
-
Combined capture of CO2 and subsequent hydrogenation allows for base/methanol-promoted homogeneous hydrogenation of CO2 to methyl formate. The CO2, captured as an amidinium methyl carbonate, reacts with H2 with no applied pressure of CO2 in the presence of a catalyst to produce sequentially amidinium formate, then methyl formate. The production of methyl formate releases the base back into the system, thereby reducing one of the flaws of catalytic hydrogenations of CO2: the notable consumption of one mole of base per mole of formate produced. The reaction proceeds under 20 atm of H2 with selectivity to formate favored by the presence of excess base and lower temperatures (110 °C), while excess alcohol and higher temperatures (140 °C) favor methyl formate. Known CO2 hydrogenation catalysts are active in the ionic liquid medium with turnover numbers as high as 5000. It is unclear as to whether the alkyl carbonate or CO2 is hydrogenated, as we show they are in equilibrium in this system. The availability of both CO2 and the alkyl carbonate as reactive species may result in new catalyst designs and free energy pathways for CO2 that may entail different selectivity or kinetic activity.
- Yadav, Mahendra,Linehan, John C.,Karkamkar, Abhijeet J.,Van Der Eide, Edwin,Heldebrant, David J.
-
p. 9849 - 9854
(2015/02/19)
-
- An integrated process of CO2 capture and in situ hydrogenation to formate using a tunable ethoxyl-functionalized amidine and Rh/bisphosphine system
-
An integrated process of CO2 capture and in situ hydrogenation into formate was achieved in 95-99% yield using a tunable ethoxyl-functionalized amidine and Rh/bisphosphine system, being regarded as an alternative carbon capture and utilization approach to supply fuel-related products, to circumvent the energy penalty in carbon capture and storage. CO2 was captured by non-volatile amidine derivatives with simultaneous activation to form zwitterionic amidinium carbonate, and subsequent hydrogenation was facilitated by Rh/bisphosphine. The adsorption capacity and hydrogenation efficiency can be optimized by tuning the ethoxyl side chain. Particularly, the alkanolamidine bearing an intramolecular hydrogen donor derived from 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) gave both a high CO2 uptake (molar ratio of 0.95:1) and excellent hydrogenation yield (99%). Furthermore, the silica-supported alkanolamidine was readily recovered and reused with the retention of good performance. This kind of carbon capture and utilization pathway could be a potential energy-saving option for industrial upgrading of CO2 from waste to fuel-related products in a carbon neutral manner.
- Li, Yu-Nong,He, Liang-Nian,Lang, Xian-Dong,Liu, Xiao-Fang,Zhang, Shuai
-
p. 49995 - 50002
(2015/01/08)
-
- 1,3-Dimethylimidazolium-2-carboxylate: A zwitterionic salt for the efficient synthesis of vicinal diols from cyclic carbonates
-
The development of efficient, cheap and recyclable catalysts for reactions under mild reaction conditions is a very attractive topic in green chemistry. Herein, a series of basic ionic liquids (ILs) were investigated as catalysts for the synthesis of vicinal diols via the hydrolysis of cyclic carbonates in order to improve this kind of synthetic process. The effects of the IL structure, the molar ratio of cyclic carbonate to water, and various reaction parameters on the catalytic performance were investigated in detail. It was found that 1,3-dimethylimidazolium-2-carboxylate, a simple halogen-free zwitterionic catalyst, showed high activity (a space-time yield of 1086 h-1) and excellent selectivity for the preparation of ethylene glycol via the hydrolysis of ethylene carbonate. The catalyst could be reused over six times without obvious loss of catalytic activity. Also, it was applicable to a variety of cyclic carbonates for the production of their corresponding vicinal diols with high yields and selectivities. A possible catalytic cycle for this kind of catalytic process was proposed based on the experimental results, NMR spectroscopy and theoretical calculations. This reaction protocol opens a new possibility for chemical synthesis as a substitution for traditional base or basic ILs. This journal is the Partner Organisations 2014.
- Sun, Jian,Yao, Xiaoqian,Cheng, Weiguo,Zhang, Suojiang
-
supporting information
p. 3297 - 3304
(2014/06/10)
-
- A rechargeable hydrogen battery based on Ru catalysis
-
Apart from energy generation, the storage and liberation of energy are among the major problems in establishing a sustainable energy supply chain. Herein we report the development of a rechargeable H2 battery which is based on the principle of the Ru-catalyzed hydrogenation of CO2 to formic acid (charging process) and the Ru-catalyzed decomposition of formic acid to CO2 and H2 (discharging process). Both processes are driven by the same catalyst at elevated temperature either under pressure (charging process) or pressure-free conditions (discharging process). Up to five charging-discharging cycles were performed without decrease of storage capacity. The resulting CO2/H2 mixture is free of CO and can be employed directly in fuel-cell technology. Simple but efficient: A readily accessible Ru catalyst is the basis for a reversible H 2/CO2-driven battery. At elevated temperatures both the reduction of CO2 to formic acid and the decomposition of formic acid were realized with 0.075 mol % of the Ru complex. Several charging and discharging cycles were performed with comparable storage-release efficiency. Furthermore, the partial removal of defined gas amounts is possible under pressure.
- Hsu, Shih-Fan,Rommel, Susanne,Eversfield, Philipp,Muller, Keven,Klemm, Elias,Thiel, Werner R.,Plietker, Bernd
-
supporting information
p. 7074 - 7078
(2014/07/08)
-