Ruthenium(II)-Catalyzed Hydrogenation of Carbon Dioxide to Formic Acid. Theoretical Study of Real Catalyst, Ligand Effects, and Solvation Effects

Abstract

Ruthenium-catalyzed hydrogenation of carbon dioxide to formic acid was theoretically investigated with DFT and MP4(SDQ) methods, where a real catalyst, cis-Ru(H)2(PMe3)3, was employed in calculations and compared with a model catalyst, cis-Ru(H)2(PH3)3. Significant differences between the real and model systems are observed in CO2 insertion into the Ru(II)-H bond, isomerization of a ruthenium(II) eta1-formate intermediate, and metathesis of the eta1-formate intermediate with a dihydrogen molecule. All these reactions more easily occur in the real system than in the model system. The differences are interpreted in terms that PMe3 is more donating than PH3 and the trans-influence of PMe3 is stronger than that of PH3. The rate-determining step is the CO2 insertion into the Ru(II)-H bond. Its deltaG(o++) value is 16.8 (6.8) kcal/mol, where the value without parentheses is calculated with the MP4(SDQ) method and that in parentheses is calculated with the DFT method. Because this insertion is considerably endothermic, the coordination of the dihydrogen molecule with the ruthenium(II)-eta1-formate intermediate must necessarily occur to suppress the deinsertion. This means that the reaction rate increases with increase in the pressure of dihydrogen molecule, which is consistent with the experimental results. Solvent effects were investigated with the DPCM method. The activation barrier and reaction energy of the CO2 insertion reaction moderately decrease in the order gas phase > n-heptane > THF, while the activation barrier of the metathesis considerably increases in the order gas phase < n-heptane < THF. Thus, a polar solvent should be used because the insertion reaction is the rate-determining step.

Recent advances in catalytic hydrogenation of carbon dioxide

“…For example, from a theoretical point of review, the rate-determining step is CO 2 insertion into a ruthenium hydride complex, which, in contrast, is a facile step in experimental studies. [292][293][294][295] Musashi and Sakaki presented a mechanistic investigation regarding the rhodium(III)-catalyzed CO 2 hydrogenation to formic acid. 296 The first step of the reaction is the insertion of CO 2 into the Rh(III)-H bond of the active species [RhH 2 (PH 3 ) 2 (H 2 O)] + .…”

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

“…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).…”

Activation and dissociation of CO2 on the (001), (011), and (111) surfaces of mackinawite (FeS): A dispersion-corrected DFT study

“…2 A significant number of studies exist in the literature regarding the adsorption, activation, and conversion of CO 2 using both heterogeneous, e.g., on metal/metal oxide surfaces [8][9][10][11] or metal-organic frameworks, [12][13][14][15] and homogeneous reactions, e.g., transition metal complexes. [16][17][18][19][20][21] More recently, transition metal sulfides have attracted significant attention for catalytic applications owing to their low cost, natural abundance, and prominent catalytic features. MoS 2 for instance has been widely used as an efficient catalyst for water splitting 22,23 and hydrodesulphurization, 24,25 whereas a recent report has shown its superior CO 2 reduction performance in an ionic liquid, compared to the noble metals, with a a) Electronic addresses: N.Y.Dzade@uu.nl and N.H.Deleeuw@uu.nl high current density and low overpotential (54 mV).…”