Catalytic deoxygenation of terminal-diols under acidic aqueous conditions by the ruthenium complexes [(η6-arene)Ru(X)(N∩N)](OTf)n, X=H2O, H, η6-arene=p-Me-iPr-C6H4, C6Me6, N∩N=bipy, phen, 6,6′-diamino-bipy, 2,9-diamino-phen, n=1, 2)

In Situ Generation of Catalytically Relevant Nanoparticles from a Molecular Pincer Iridium Precatalyst during Polyol Deoxygenation

“…The detection of nanoparticles generated from ( t Bu POCOP)­IrCO under these acidic reducing conditions may have important implications for selective biomass deoxygenation, in particular, the longstanding challenge of converting glycerol to 1,3-propanediol. , A commonly invoked mechanism for this process is the dehydration–hydrogenation mechanism, which has been suggested in previous deoxygenation studies involving ( t Bu POCOP)­IrCO under acidic conditions. − Schlaf and co-workers have noted that heterogeneous catalysts for glycerol deoxygenation by dehydration–hydrogenation mechanism strongly favor the formation of 1-propanol rather than the more valuable 1,3-propanediol and suggest that this can be explained by the surface of the heterogeneous transition metal particle acting as an acid catalyst that promotes dehydration of the sterically favored terminal position . They then propose that an effective catalyst for the deoxygenation of glycerol to 1,3-propanediol by a dehydration–hydrogenation mechanism will need to be homogeneous so that the dehydration step will occur at the electronically favored internal site.…”

Cyclopentadienyl–Ru(II)–Pyridylamine Complexes: Synthesis, X-ray Structure, and Application in Catalytic Transformation of Bio-Derived Furans to Levulinic Acid and Diketones in Water

“…Moreover, as inferred from the Hg poisoning experiments, no decomposition of [Ru]-2 catalysts to Ru nanoparticles is observed under the catalytic reaction conditions (>120 °C in water). The observed high stability of [Ru]-2 catalysts can be attributed to the strong coordination of η 5 -Cp to the Ru center, while η 6 -arene–Ru­(II) complexes decomposed to Ru nanoparticles at a higher temperature. , Moreover, the high aqueous and thermal stability of the studied η 5 -Cp–Ru­(II)–pyridylamine complexes is also reflected in their two-fold higher catalytic activity (84% yield of LA, 6 h, 120 °C, 12 mmol of HCOOH) over the analogous η 6 -arene–Ru­(II) (42% yield of LA, 8 h, 100 °C, 12 mmol of HCOOH) . Notably, previously explored catalysts based on a η 5 -Cp*–Ir complex or other metal nanoparticle catalysts (Pd/Al 2 O 3 or Au/Nb 2 O 5 ) required high H 2 gas pressure (5–80 bar) and higher temperature (120–170 °C) for analogous catalytic transformations (Table S9 in the Supporting Information). − Therefore, the studied η 5 -Cp–Ru­(II)–pyridylamine complexes represent a class of highly active catalysts with high thermal and aqueous stability, showing catalytic activity higher than or on par with that of previously reported catalytic systems.…”

“…Notably, using formic acid is advantageous, as it can act as an efficient hydrogenating source as well as controls the pH of the catalytic reaction and hence the selectivity of the product. Moreover, η 6 -arene–ruthenium complexes usually underwent decomposition to ruthenium metal at higher temperature (>120 °C) and lost their catalytic activity. , On the other hand, the ruthenium–cyclopentadienyl-based complexes displayed high stability in water and acid at a higher temperature in comparison to η 6 -arene–ruthenium complexes. , It has been hypothesized that the anionic cyclopentadienyl ligand bonded strongly with the Ru 2+ center, in comparison to the weakly bonded neutral η 6 -arene ligand. , Moreover, it has also been suggested that, due to the anionic cyclopentadienyl ligand, the metal center may have a higher electron density and it may therefore substantially influence the catalytic activity of the resulting η 5 -Cp–Ru­(II) complexes, in comparison to the η 6 -arene ligand.…”

Proton-responsive Ruthenium(II) Catalysts for the Solvolysis of Ammonia-Borane

“…[Ru­(p-Cym)­Cl 2 ] 2 , 2,2′-bipyridine, amine-boranes, and other general chemicals were obtained from commercial sources and used without further purification. [Ru­(p-Cym)­(dhbp)­Cl]Cl ( 1 ), [Ru­(p-Cym)­(bipy)­Cl]­Cl ( V ), [Ir­(Cp*)­(dhbp)­(H 2 O)]­SO 4 ( VI ), and dhbp were prepared following published methodologies. ,, Solvents were dried by known procedures and distilled under nitrogen from appropriate drying agents prior to use. Manipulations and reactions involving air- and/or moisture-sensitive organometallic compounds were performed under an atmosphere of dry nitrogen using standard Schlenk techniques.…”