A Cationic Ru(II) Complex Intercalated into Zirconium Phosphate Layers Catalyzes Selective Hydrogenation via Heterolytic Hydrogen Activation

Abstract

Catalytic hydrogenations constitute economic and clean transformations to produce pharmaceutical and a multitude of fine chemicals in chemical industry. Herein, we report a cationic Ru(II) complex intercalated into zirconium phosphate (ZrP) layers that enables the efficient catalytic conversion of furfural and other biomass-derived carbonyl compounds into the corresponding alcohols through selective hydrogenation of C=O group. The ZrP layers acted not only as a support for the Ru-complex, but also as the new ligands to tune the Ru(II) center via forming RuÀ O bond. The resulting catalysts exhibit excellent catalytic performance and can be easily recycled for six times without significant loss of activity and selectivity. The Ru(II) complex-intercalated catalysts have been characterized by XRD, SEM, HRTEM, HAADF-STEM, XPS, FT-IR, DR-UV/Vis, EXAFS and XANES. Especially, it is observed that the appropriate interlayer spacing between ZrP layers is favorable to stabilize the Ru(II) complex. Notably, on the basis of the further characterization and density functional theory (DFT) calculation, it is identified that the interaction of cationic Ru(II) complex and PÀ OH group within ZrP layers leads to the high catalytic performance in selective hydrogenation, and the newly formed RuÀ OÀ P species plays a crucial role in the heterolytic hydrogen activation and selective hydrogenation of biomass-derived compounds containing a carbonyl group.

Ruthenium Single-Atom Anchored in Polyoxometalate-Ionic Liquids for N-Formylation of Amines with CO2 and H2

“…Besides, the peak of Ru 3p 3/2 around 462.3 eV is attributed to Ru 2+ species, confirming that the Ru center maintained its Ru 2+ state after being incorporated into the POM framework (Figure 2d). 60 The X-ray adsorption fine structure (XAFS) is performed to provide more detailed information on the valence state and chemical environment of Ru sites. XANES spectra of the model compounds (Ru foil, RuO 2 ) as well as K-SiWRu and TOMA-SiWRu samples are shown in Figure 3a.…”

Solvent-Assisted Ruthenium Complex Catalyzes Hydrogenation and the Reductive Amination of Carbon Dioxide

“…In our previous work, it has been demonstrated that the substitution of Ru−Cl coordination bond by Ru−O coordination could promote heterolytic hydrogen activation. 63 Therefore, for the present catalytic system, the in situ formed Ru−OAc complex might also facilitate the dissociation of hydrogen into H δ+ and H δ− , which tended to hydrogenate polar unsaturated C�O group (Table S2, entries 9 and 11), enabling the hydrogenation of polar unsaturated carbonyl bond. 76,78 Usually, ancillary ligands like basic bisphosphine and diamine (en) ligands were needed to stabilize the transition state metal center after the hydride transfer step.…”

“…Notably, The Ru−O bond of the Ru−OAc complex could promote the heterolytic cleavage of H 2 (species II) according to our and other group studies. 63,78 The resulting H δ− and H δ+ interacted with the Ru center and the − OAc anion, respectively (species III). Then the hydride attacked the C δ+ of C�O, and − OAc was coordinated to the Ru center to stabilize the H δ+ species (species IV).…”

“…Recently, our group has reported a cationic Ru­(II) complex intercalated into zirconium phosphate layers, which enables the efficient catalytic conversion of furfural and other biomass-derived carbonyl compounds into the corresponding alcohols through selective hydrogenation of CO group. From activity evaluation and DFT calculation, we proposed that the Ru–O active sites on the catalyst were responsible for H 2 heterolytic dissociation, resulting in a crucial intermediate Ru–H δ− species, which favored selective hydrogenation of polar unsaturated CO group . As a continuation of our efforts and the idea of green chemistry to design easily accessible, cheap, stable Ru complexes for catalytic hydrogenation, in this work we attempted to develop a highly efficient, robust catalytic system consisting of a ruthenium hydride complex [RuH­(CO)­(dppp)­(en)]Cl (en = ethylenediamine) and commercially available tetrabutylammonium acetate (TBAOAc) as a low-temperature molten salt solvent for the hydrogenation of ML to GVL under mild conditions (1.0 MPa, 100 °C, 1 h), yielding 99% conversion of ML and 99% GVL selectivity (Scheme C).…”

“…From activity evaluation and DFT calculation, we proposed that the Ru−O active sites on the catalyst were responsible for H 2 heterolytic dissociation, resulting in a crucial intermediate Ru−H δ− species, which favored selective hydrogenation of polar unsaturated C�O group. 63 As a continuation of our efforts and the idea of green chemistry to design easily accessible, cheap, stable Ru complexes for catalytic hydrogenation, in this work we attempted to develop a highly efficient, robust catalytic system consisting of a ruthenium hydride complex [RuH(CO)(dppp)(en)]Cl (en = ethylenediamine) and commercially available tetrabutylammonium acetate (TBAOAc) as a low-temperature molten salt solvent for the hydrogenation of ML to GVL under mild conditions (1.0 MPa, 100 °C, 1 h), yielding 99% conversion of ML and 99% GVL selectivity (Scheme 1C). Based on NMR and HRMS studies, we suggest that [Ru(OAc)(CO)(dppp)(en)] + species could form under reaction conditions, which was more favorable for H 2 activation and dissociation.…”